Source file src/reflect/value.go

Documentation: reflect

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package reflect
     6  
     7  import (
     8  	"errors"
     9  	"internal/abi"
    10  	"internal/goarch"
    11  	"internal/itoa"
    12  	"internal/unsafeheader"
    13  	"math"
    14  	"runtime"
    15  	"unsafe"
    16  )
    17  
    18  // Value is the reflection interface to a Go value.
    19  //
    20  // Not all methods apply to all kinds of values. Restrictions,
    21  // if any, are noted in the documentation for each method.
    22  // Use the Kind method to find out the kind of value before
    23  // calling kind-specific methods. Calling a method
    24  // inappropriate to the kind of type causes a run time panic.
    25  //
    26  // The zero Value represents no value.
    27  // Its IsValid method returns false, its Kind method returns Invalid,
    28  // its String method returns "<invalid Value>", and all other methods panic.
    29  // Most functions and methods never return an invalid value.
    30  // If one does, its documentation states the conditions explicitly.
    31  //
    32  // A Value can be used concurrently by multiple goroutines provided that
    33  // the underlying Go value can be used concurrently for the equivalent
    34  // direct operations.
    35  //
    36  // To compare two Values, compare the results of the Interface method.
    37  // Using == on two Values does not compare the underlying values
    38  // they represent.
    39  type Value struct {
    40  	// typ holds the type of the value represented by a Value.
    41  	typ *rtype
    42  
    43  	// Pointer-valued data or, if flagIndir is set, pointer to data.
    44  	// Valid when either flagIndir is set or typ.pointers() is true.
    45  	ptr unsafe.Pointer
    46  
    47  	// flag holds metadata about the value.
    48  	// The lowest bits are flag bits:
    49  	//	- flagStickyRO: obtained via unexported not embedded field, so read-only
    50  	//	- flagEmbedRO: obtained via unexported embedded field, so read-only
    51  	//	- flagIndir: val holds a pointer to the data
    52  	//	- flagAddr: v.CanAddr is true (implies flagIndir)
    53  	//	- flagMethod: v is a method value.
    54  	// The next five bits give the Kind of the value.
    55  	// This repeats typ.Kind() except for method values.
    56  	// The remaining 23+ bits give a method number for method values.
    57  	// If flag.kind() != Func, code can assume that flagMethod is unset.
    58  	// If ifaceIndir(typ), code can assume that flagIndir is set.
    59  	flag
    60  
    61  	// A method value represents a curried method invocation
    62  	// like r.Read for some receiver r. The typ+val+flag bits describe
    63  	// the receiver r, but the flag's Kind bits say Func (methods are
    64  	// functions), and the top bits of the flag give the method number
    65  	// in r's type's method table.
    66  }
    67  
    68  type flag uintptr
    69  
    70  const (
    71  	flagKindWidth        = 5 // there are 27 kinds
    72  	flagKindMask    flag = 1<<flagKindWidth - 1
    73  	flagStickyRO    flag = 1 << 5
    74  	flagEmbedRO     flag = 1 << 6
    75  	flagIndir       flag = 1 << 7
    76  	flagAddr        flag = 1 << 8
    77  	flagMethod      flag = 1 << 9
    78  	flagMethodShift      = 10
    79  	flagRO          flag = flagStickyRO | flagEmbedRO
    80  )
    81  
    82  func (f flag) kind() Kind {
    83  	return Kind(f & flagKindMask)
    84  }
    85  
    86  func (f flag) ro() flag {
    87  	if f&flagRO != 0 {
    88  		return flagStickyRO
    89  	}
    90  	return 0
    91  }
    92  
    93  // pointer returns the underlying pointer represented by v.
    94  // v.Kind() must be Pointer, Map, Chan, Func, or UnsafePointer
    95  // if v.Kind() == Pointer, the base type must not be go:notinheap.
    96  func (v Value) pointer() unsafe.Pointer {
    97  	if v.typ.size != goarch.PtrSize || !v.typ.pointers() {
    98  		panic("can't call pointer on a non-pointer Value")
    99  	}
   100  	if v.flag&flagIndir != 0 {
   101  		return *(*unsafe.Pointer)(v.ptr)
   102  	}
   103  	return v.ptr
   104  }
   105  
   106  // packEface converts v to the empty interface.
   107  func packEface(v Value) any {
   108  	t := v.typ
   109  	var i any
   110  	e := (*emptyInterface)(unsafe.Pointer(&i))
   111  	// First, fill in the data portion of the interface.
   112  	switch {
   113  	case ifaceIndir(t):
   114  		if v.flag&flagIndir == 0 {
   115  			panic("bad indir")
   116  		}
   117  		// Value is indirect, and so is the interface we're making.
   118  		ptr := v.ptr
   119  		if v.flag&flagAddr != 0 {
   120  			// TODO: pass safe boolean from valueInterface so
   121  			// we don't need to copy if safe==true?
   122  			c := unsafe_New(t)
   123  			typedmemmove(t, c, ptr)
   124  			ptr = c
   125  		}
   126  		e.word = ptr
   127  	case v.flag&flagIndir != 0:
   128  		// Value is indirect, but interface is direct. We need
   129  		// to load the data at v.ptr into the interface data word.
   130  		e.word = *(*unsafe.Pointer)(v.ptr)
   131  	default:
   132  		// Value is direct, and so is the interface.
   133  		e.word = v.ptr
   134  	}
   135  	// Now, fill in the type portion. We're very careful here not
   136  	// to have any operation between the e.word and e.typ assignments
   137  	// that would let the garbage collector observe the partially-built
   138  	// interface value.
   139  	e.typ = t
   140  	return i
   141  }
   142  
   143  // unpackEface converts the empty interface i to a Value.
   144  func unpackEface(i any) Value {
   145  	e := (*emptyInterface)(unsafe.Pointer(&i))
   146  	// NOTE: don't read e.word until we know whether it is really a pointer or not.
   147  	t := e.typ
   148  	if t == nil {
   149  		return Value{}
   150  	}
   151  	f := flag(t.Kind())
   152  	if ifaceIndir(t) {
   153  		f |= flagIndir
   154  	}
   155  	return Value{t, e.word, f}
   156  }
   157  
   158  // A ValueError occurs when a Value method is invoked on
   159  // a Value that does not support it. Such cases are documented
   160  // in the description of each method.
   161  type ValueError struct {
   162  	Method string
   163  	Kind   Kind
   164  }
   165  
   166  func (e *ValueError) Error() string {
   167  	if e.Kind == 0 {
   168  		return "reflect: call of " + e.Method + " on zero Value"
   169  	}
   170  	return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value"
   171  }
   172  
   173  // valueMethodName returns the name of the exported calling method on Value.
   174  func valueMethodName() string {
   175  	var pc [5]uintptr
   176  	n := runtime.Callers(1, pc[:])
   177  	frames := runtime.CallersFrames(pc[:n])
   178  	var frame runtime.Frame
   179  	for more := true; more; {
   180  		const prefix = "reflect.Value."
   181  		frame, more = frames.Next()
   182  		name := frame.Function
   183  		if len(name) > len(prefix) && name[:len(prefix)] == prefix {
   184  			methodName := name[len(prefix):]
   185  			if len(methodName) > 0 && 'A' <= methodName[0] && methodName[0] <= 'Z' {
   186  				return name
   187  			}
   188  		}
   189  	}
   190  	return "unknown method"
   191  }
   192  
   193  // emptyInterface is the header for an interface{} value.
   194  type emptyInterface struct {
   195  	typ  *rtype
   196  	word unsafe.Pointer
   197  }
   198  
   199  // nonEmptyInterface is the header for an interface value with methods.
   200  type nonEmptyInterface struct {
   201  	// see ../runtime/iface.go:/Itab
   202  	itab *struct {
   203  		ityp *rtype // static interface type
   204  		typ  *rtype // dynamic concrete type
   205  		hash uint32 // copy of typ.hash
   206  		_    [4]byte
   207  		fun  [100000]unsafe.Pointer // method table
   208  	}
   209  	word unsafe.Pointer
   210  }
   211  
   212  // mustBe panics if f's kind is not expected.
   213  // Making this a method on flag instead of on Value
   214  // (and embedding flag in Value) means that we can write
   215  // the very clear v.mustBe(Bool) and have it compile into
   216  // v.flag.mustBe(Bool), which will only bother to copy the
   217  // single important word for the receiver.
   218  func (f flag) mustBe(expected Kind) {
   219  	// TODO(mvdan): use f.kind() again once mid-stack inlining gets better
   220  	if Kind(f&flagKindMask) != expected {
   221  		panic(&ValueError{valueMethodName(), f.kind()})
   222  	}
   223  }
   224  
   225  // mustBeExported panics if f records that the value was obtained using
   226  // an unexported field.
   227  func (f flag) mustBeExported() {
   228  	if f == 0 || f&flagRO != 0 {
   229  		f.mustBeExportedSlow()
   230  	}
   231  }
   232  
   233  func (f flag) mustBeExportedSlow() {
   234  	if f == 0 {
   235  		panic(&ValueError{valueMethodName(), Invalid})
   236  	}
   237  	if f&flagRO != 0 {
   238  		panic("reflect: " + valueMethodName() + " using value obtained using unexported field")
   239  	}
   240  }
   241  
   242  // mustBeAssignable panics if f records that the value is not assignable,
   243  // which is to say that either it was obtained using an unexported field
   244  // or it is not addressable.
   245  func (f flag) mustBeAssignable() {
   246  	if f&flagRO != 0 || f&flagAddr == 0 {
   247  		f.mustBeAssignableSlow()
   248  	}
   249  }
   250  
   251  func (f flag) mustBeAssignableSlow() {
   252  	if f == 0 {
   253  		panic(&ValueError{valueMethodName(), Invalid})
   254  	}
   255  	// Assignable if addressable and not read-only.
   256  	if f&flagRO != 0 {
   257  		panic("reflect: " + valueMethodName() + " using value obtained using unexported field")
   258  	}
   259  	if f&flagAddr == 0 {
   260  		panic("reflect: " + valueMethodName() + " using unaddressable value")
   261  	}
   262  }
   263  
   264  // Addr returns a pointer value representing the address of v.
   265  // It panics if CanAddr() returns false.
   266  // Addr is typically used to obtain a pointer to a struct field
   267  // or slice element in order to call a method that requires a
   268  // pointer receiver.
   269  func (v Value) Addr() Value {
   270  	if v.flag&flagAddr == 0 {
   271  		panic("reflect.Value.Addr of unaddressable value")
   272  	}
   273  	// Preserve flagRO instead of using v.flag.ro() so that
   274  	// v.Addr().Elem() is equivalent to v (#32772)
   275  	fl := v.flag & flagRO
   276  	return Value{v.typ.ptrTo(), v.ptr, fl | flag(Pointer)}
   277  }
   278  
   279  // Bool returns v's underlying value.
   280  // It panics if v's kind is not Bool.
   281  func (v Value) Bool() bool {
   282  	// panicNotBool is split out to keep Bool inlineable.
   283  	if v.kind() != Bool {
   284  		v.panicNotBool()
   285  	}
   286  	return *(*bool)(v.ptr)
   287  }
   288  
   289  func (v Value) panicNotBool() {
   290  	v.mustBe(Bool)
   291  }
   292  
   293  var bytesType = TypeOf(([]byte)(nil)).(*rtype)
   294  
   295  // Bytes returns v's underlying value.
   296  // It panics if v's underlying value is not a slice of bytes or
   297  // an addressable array of bytes.
   298  func (v Value) Bytes() []byte {
   299  	// bytesSlow is split out to keep Bytes inlineable for unnamed []byte.
   300  	if v.typ == bytesType {
   301  		return *(*[]byte)(v.ptr)
   302  	}
   303  	return v.bytesSlow()
   304  }
   305  
   306  func (v Value) bytesSlow() []byte {
   307  	switch v.kind() {
   308  	case Slice:
   309  		if v.typ.Elem().Kind() != Uint8 {
   310  			panic("reflect.Value.Bytes of non-byte slice")
   311  		}
   312  		// Slice is always bigger than a word; assume flagIndir.
   313  		return *(*[]byte)(v.ptr)
   314  	case Array:
   315  		if v.typ.Elem().Kind() != Uint8 {
   316  			panic("reflect.Value.Bytes of non-byte array")
   317  		}
   318  		if !v.CanAddr() {
   319  			panic("reflect.Value.Bytes of unaddressable byte array")
   320  		}
   321  		p := (*byte)(v.ptr)
   322  		n := int((*arrayType)(unsafe.Pointer(v.typ)).len)
   323  		return unsafe.Slice(p, n)
   324  	}
   325  	panic(&ValueError{"reflect.Value.Bytes", v.kind()})
   326  }
   327  
   328  // runes returns v's underlying value.
   329  // It panics if v's underlying value is not a slice of runes (int32s).
   330  func (v Value) runes() []rune {
   331  	v.mustBe(Slice)
   332  	if v.typ.Elem().Kind() != Int32 {
   333  		panic("reflect.Value.Bytes of non-rune slice")
   334  	}
   335  	// Slice is always bigger than a word; assume flagIndir.
   336  	return *(*[]rune)(v.ptr)
   337  }
   338  
   339  // CanAddr reports whether the value's address can be obtained with Addr.
   340  // Such values are called addressable. A value is addressable if it is
   341  // an element of a slice, an element of an addressable array,
   342  // a field of an addressable struct, or the result of dereferencing a pointer.
   343  // If CanAddr returns false, calling Addr will panic.
   344  func (v Value) CanAddr() bool {
   345  	return v.flag&flagAddr != 0
   346  }
   347  
   348  // CanSet reports whether the value of v can be changed.
   349  // A Value can be changed only if it is addressable and was not
   350  // obtained by the use of unexported struct fields.
   351  // If CanSet returns false, calling Set or any type-specific
   352  // setter (e.g., SetBool, SetInt) will panic.
   353  func (v Value) CanSet() bool {
   354  	return v.flag&(flagAddr|flagRO) == flagAddr
   355  }
   356  
   357  // Call calls the function v with the input arguments in.
   358  // For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]).
   359  // Call panics if v's Kind is not Func.
   360  // It returns the output results as Values.
   361  // As in Go, each input argument must be assignable to the
   362  // type of the function's corresponding input parameter.
   363  // If v is a variadic function, Call creates the variadic slice parameter
   364  // itself, copying in the corresponding values.
   365  func (v Value) Call(in []Value) []Value {
   366  	v.mustBe(Func)
   367  	v.mustBeExported()
   368  	return v.call("Call", in)
   369  }
   370  
   371  // CallSlice calls the variadic function v with the input arguments in,
   372  // assigning the slice in[len(in)-1] to v's final variadic argument.
   373  // For example, if len(in) == 3, v.CallSlice(in) represents the Go call v(in[0], in[1], in[2]...).
   374  // CallSlice panics if v's Kind is not Func or if v is not variadic.
   375  // It returns the output results as Values.
   376  // As in Go, each input argument must be assignable to the
   377  // type of the function's corresponding input parameter.
   378  func (v Value) CallSlice(in []Value) []Value {
   379  	v.mustBe(Func)
   380  	v.mustBeExported()
   381  	return v.call("CallSlice", in)
   382  }
   383  
   384  var callGC bool // for testing; see TestCallMethodJump and TestCallArgLive
   385  
   386  const debugReflectCall = false
   387  
   388  func (v Value) call(op string, in []Value) []Value {
   389  	// Get function pointer, type.
   390  	t := (*funcType)(unsafe.Pointer(v.typ))
   391  	var (
   392  		fn       unsafe.Pointer
   393  		rcvr     Value
   394  		rcvrtype *rtype
   395  	)
   396  	if v.flag&flagMethod != 0 {
   397  		rcvr = v
   398  		rcvrtype, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift)
   399  	} else if v.flag&flagIndir != 0 {
   400  		fn = *(*unsafe.Pointer)(v.ptr)
   401  	} else {
   402  		fn = v.ptr
   403  	}
   404  
   405  	if fn == nil {
   406  		panic("reflect.Value.Call: call of nil function")
   407  	}
   408  
   409  	isSlice := op == "CallSlice"
   410  	n := t.NumIn()
   411  	isVariadic := t.IsVariadic()
   412  	if isSlice {
   413  		if !isVariadic {
   414  			panic("reflect: CallSlice of non-variadic function")
   415  		}
   416  		if len(in) < n {
   417  			panic("reflect: CallSlice with too few input arguments")
   418  		}
   419  		if len(in) > n {
   420  			panic("reflect: CallSlice with too many input arguments")
   421  		}
   422  	} else {
   423  		if isVariadic {
   424  			n--
   425  		}
   426  		if len(in) < n {
   427  			panic("reflect: Call with too few input arguments")
   428  		}
   429  		if !isVariadic && len(in) > n {
   430  			panic("reflect: Call with too many input arguments")
   431  		}
   432  	}
   433  	for _, x := range in {
   434  		if x.Kind() == Invalid {
   435  			panic("reflect: " + op + " using zero Value argument")
   436  		}
   437  	}
   438  	for i := 0; i < n; i++ {
   439  		if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) {
   440  			panic("reflect: " + op + " using " + xt.String() + " as type " + targ.String())
   441  		}
   442  	}
   443  	if !isSlice && isVariadic {
   444  		// prepare slice for remaining values
   445  		m := len(in) - n
   446  		slice := MakeSlice(t.In(n), m, m)
   447  		elem := t.In(n).Elem()
   448  		for i := 0; i < m; i++ {
   449  			x := in[n+i]
   450  			if xt := x.Type(); !xt.AssignableTo(elem) {
   451  				panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op)
   452  			}
   453  			slice.Index(i).Set(x)
   454  		}
   455  		origIn := in
   456  		in = make([]Value, n+1)
   457  		copy(in[:n], origIn)
   458  		in[n] = slice
   459  	}
   460  
   461  	nin := len(in)
   462  	if nin != t.NumIn() {
   463  		panic("reflect.Value.Call: wrong argument count")
   464  	}
   465  	nout := t.NumOut()
   466  
   467  	// Register argument space.
   468  	var regArgs abi.RegArgs
   469  
   470  	// Compute frame type.
   471  	frametype, framePool, abid := funcLayout(t, rcvrtype)
   472  
   473  	// Allocate a chunk of memory for frame if needed.
   474  	var stackArgs unsafe.Pointer
   475  	if frametype.size != 0 {
   476  		if nout == 0 {
   477  			stackArgs = framePool.Get().(unsafe.Pointer)
   478  		} else {
   479  			// Can't use pool if the function has return values.
   480  			// We will leak pointer to args in ret, so its lifetime is not scoped.
   481  			stackArgs = unsafe_New(frametype)
   482  		}
   483  	}
   484  	frameSize := frametype.size
   485  
   486  	if debugReflectCall {
   487  		println("reflect.call", t.String())
   488  		abid.dump()
   489  	}
   490  
   491  	// Copy inputs into args.
   492  
   493  	// Handle receiver.
   494  	inStart := 0
   495  	if rcvrtype != nil {
   496  		// Guaranteed to only be one word in size,
   497  		// so it will only take up exactly 1 abiStep (either
   498  		// in a register or on the stack).
   499  		switch st := abid.call.steps[0]; st.kind {
   500  		case abiStepStack:
   501  			storeRcvr(rcvr, stackArgs)
   502  		case abiStepPointer:
   503  			storeRcvr(rcvr, unsafe.Pointer(&regArgs.Ptrs[st.ireg]))
   504  			fallthrough
   505  		case abiStepIntReg:
   506  			storeRcvr(rcvr, unsafe.Pointer(&regArgs.Ints[st.ireg]))
   507  		case abiStepFloatReg:
   508  			storeRcvr(rcvr, unsafe.Pointer(&regArgs.Floats[st.freg]))
   509  		default:
   510  			panic("unknown ABI parameter kind")
   511  		}
   512  		inStart = 1
   513  	}
   514  
   515  	// Handle arguments.
   516  	for i, v := range in {
   517  		v.mustBeExported()
   518  		targ := t.In(i).(*rtype)
   519  		// TODO(mknyszek): Figure out if it's possible to get some
   520  		// scratch space for this assignment check. Previously, it
   521  		// was possible to use space in the argument frame.
   522  		v = v.assignTo("reflect.Value.Call", targ, nil)
   523  	stepsLoop:
   524  		for _, st := range abid.call.stepsForValue(i + inStart) {
   525  			switch st.kind {
   526  			case abiStepStack:
   527  				// Copy values to the "stack."
   528  				addr := add(stackArgs, st.stkOff, "precomputed stack arg offset")
   529  				if v.flag&flagIndir != 0 {
   530  					typedmemmove(targ, addr, v.ptr)
   531  				} else {
   532  					*(*unsafe.Pointer)(addr) = v.ptr
   533  				}
   534  				// There's only one step for a stack-allocated value.
   535  				break stepsLoop
   536  			case abiStepIntReg, abiStepPointer:
   537  				// Copy values to "integer registers."
   538  				if v.flag&flagIndir != 0 {
   539  					offset := add(v.ptr, st.offset, "precomputed value offset")
   540  					if st.kind == abiStepPointer {
   541  						// Duplicate this pointer in the pointer area of the
   542  						// register space. Otherwise, there's the potential for
   543  						// this to be the last reference to v.ptr.
   544  						regArgs.Ptrs[st.ireg] = *(*unsafe.Pointer)(offset)
   545  					}
   546  					intToReg(&regArgs, st.ireg, st.size, offset)
   547  				} else {
   548  					if st.kind == abiStepPointer {
   549  						// See the comment in abiStepPointer case above.
   550  						regArgs.Ptrs[st.ireg] = v.ptr
   551  					}
   552  					regArgs.Ints[st.ireg] = uintptr(v.ptr)
   553  				}
   554  			case abiStepFloatReg:
   555  				// Copy values to "float registers."
   556  				if v.flag&flagIndir == 0 {
   557  					panic("attempted to copy pointer to FP register")
   558  				}
   559  				offset := add(v.ptr, st.offset, "precomputed value offset")
   560  				floatToReg(&regArgs, st.freg, st.size, offset)
   561  			default:
   562  				panic("unknown ABI part kind")
   563  			}
   564  		}
   565  	}
   566  	// TODO(mknyszek): Remove this when we no longer have
   567  	// caller reserved spill space.
   568  	frameSize = align(frameSize, goarch.PtrSize)
   569  	frameSize += abid.spill
   570  
   571  	// Mark pointers in registers for the return path.
   572  	regArgs.ReturnIsPtr = abid.outRegPtrs
   573  
   574  	if debugReflectCall {
   575  		regArgs.Dump()
   576  	}
   577  
   578  	// For testing; see TestCallArgLive.
   579  	if callGC {
   580  		runtime.GC()
   581  	}
   582  
   583  	// Call.
   584  	call(frametype, fn, stackArgs, uint32(frametype.size), uint32(abid.retOffset), uint32(frameSize), &regArgs)
   585  
   586  	// For testing; see TestCallMethodJump.
   587  	if callGC {
   588  		runtime.GC()
   589  	}
   590  
   591  	var ret []Value
   592  	if nout == 0 {
   593  		if stackArgs != nil {
   594  			typedmemclr(frametype, stackArgs)
   595  			framePool.Put(stackArgs)
   596  		}
   597  	} else {
   598  		if stackArgs != nil {
   599  			// Zero the now unused input area of args,
   600  			// because the Values returned by this function contain pointers to the args object,
   601  			// and will thus keep the args object alive indefinitely.
   602  			typedmemclrpartial(frametype, stackArgs, 0, abid.retOffset)
   603  		}
   604  
   605  		// Wrap Values around return values in args.
   606  		ret = make([]Value, nout)
   607  		for i := 0; i < nout; i++ {
   608  			tv := t.Out(i)
   609  			if tv.Size() == 0 {
   610  				// For zero-sized return value, args+off may point to the next object.
   611  				// In this case, return the zero value instead.
   612  				ret[i] = Zero(tv)
   613  				continue
   614  			}
   615  			steps := abid.ret.stepsForValue(i)
   616  			if st := steps[0]; st.kind == abiStepStack {
   617  				// This value is on the stack. If part of a value is stack
   618  				// allocated, the entire value is according to the ABI. So
   619  				// just make an indirection into the allocated frame.
   620  				fl := flagIndir | flag(tv.Kind())
   621  				ret[i] = Value{tv.common(), add(stackArgs, st.stkOff, "tv.Size() != 0"), fl}
   622  				// Note: this does introduce false sharing between results -
   623  				// if any result is live, they are all live.
   624  				// (And the space for the args is live as well, but as we've
   625  				// cleared that space it isn't as big a deal.)
   626  				continue
   627  			}
   628  
   629  			// Handle pointers passed in registers.
   630  			if !ifaceIndir(tv.common()) {
   631  				// Pointer-valued data gets put directly
   632  				// into v.ptr.
   633  				if steps[0].kind != abiStepPointer {
   634  					print("kind=", steps[0].kind, ", type=", tv.String(), "\n")
   635  					panic("mismatch between ABI description and types")
   636  				}
   637  				ret[i] = Value{tv.common(), regArgs.Ptrs[steps[0].ireg], flag(tv.Kind())}
   638  				continue
   639  			}
   640  
   641  			// All that's left is values passed in registers that we need to
   642  			// create space for and copy values back into.
   643  			//
   644  			// TODO(mknyszek): We make a new allocation for each register-allocated
   645  			// value, but previously we could always point into the heap-allocated
   646  			// stack frame. This is a regression that could be fixed by adding
   647  			// additional space to the allocated stack frame and storing the
   648  			// register-allocated return values into the allocated stack frame and
   649  			// referring there in the resulting Value.
   650  			s := unsafe_New(tv.common())
   651  			for _, st := range steps {
   652  				switch st.kind {
   653  				case abiStepIntReg:
   654  					offset := add(s, st.offset, "precomputed value offset")
   655  					intFromReg(&regArgs, st.ireg, st.size, offset)
   656  				case abiStepPointer:
   657  					s := add(s, st.offset, "precomputed value offset")
   658  					*((*unsafe.Pointer)(s)) = regArgs.Ptrs[st.ireg]
   659  				case abiStepFloatReg:
   660  					offset := add(s, st.offset, "precomputed value offset")
   661  					floatFromReg(&regArgs, st.freg, st.size, offset)
   662  				case abiStepStack:
   663  					panic("register-based return value has stack component")
   664  				default:
   665  					panic("unknown ABI part kind")
   666  				}
   667  			}
   668  			ret[i] = Value{tv.common(), s, flagIndir | flag(tv.Kind())}
   669  		}
   670  	}
   671  
   672  	return ret
   673  }
   674  
   675  // callReflect is the call implementation used by a function
   676  // returned by MakeFunc. In many ways it is the opposite of the
   677  // method Value.call above. The method above converts a call using Values
   678  // into a call of a function with a concrete argument frame, while
   679  // callReflect converts a call of a function with a concrete argument
   680  // frame into a call using Values.
   681  // It is in this file so that it can be next to the call method above.
   682  // The remainder of the MakeFunc implementation is in makefunc.go.
   683  //
   684  // NOTE: This function must be marked as a "wrapper" in the generated code,
   685  // so that the linker can make it work correctly for panic and recover.
   686  // The gc compilers know to do that for the name "reflect.callReflect".
   687  //
   688  // ctxt is the "closure" generated by MakeFunc.
   689  // frame is a pointer to the arguments to that closure on the stack.
   690  // retValid points to a boolean which should be set when the results
   691  // section of frame is set.
   692  //
   693  // regs contains the argument values passed in registers and will contain
   694  // the values returned from ctxt.fn in registers.
   695  func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) {
   696  	if callGC {
   697  		// Call GC upon entry during testing.
   698  		// Getting our stack scanned here is the biggest hazard, because
   699  		// our caller (makeFuncStub) could have failed to place the last
   700  		// pointer to a value in regs' pointer space, in which case it
   701  		// won't be visible to the GC.
   702  		runtime.GC()
   703  	}
   704  	ftyp := ctxt.ftyp
   705  	f := ctxt.fn
   706  
   707  	_, _, abid := funcLayout(ftyp, nil)
   708  
   709  	// Copy arguments into Values.
   710  	ptr := frame
   711  	in := make([]Value, 0, int(ftyp.inCount))
   712  	for i, typ := range ftyp.in() {
   713  		if typ.Size() == 0 {
   714  			in = append(in, Zero(typ))
   715  			continue
   716  		}
   717  		v := Value{typ, nil, flag(typ.Kind())}
   718  		steps := abid.call.stepsForValue(i)
   719  		if st := steps[0]; st.kind == abiStepStack {
   720  			if ifaceIndir(typ) {
   721  				// value cannot be inlined in interface data.
   722  				// Must make a copy, because f might keep a reference to it,
   723  				// and we cannot let f keep a reference to the stack frame
   724  				// after this function returns, not even a read-only reference.
   725  				v.ptr = unsafe_New(typ)
   726  				if typ.size > 0 {
   727  					typedmemmove(typ, v.ptr, add(ptr, st.stkOff, "typ.size > 0"))
   728  				}
   729  				v.flag |= flagIndir
   730  			} else {
   731  				v.ptr = *(*unsafe.Pointer)(add(ptr, st.stkOff, "1-ptr"))
   732  			}
   733  		} else {
   734  			if ifaceIndir(typ) {
   735  				// All that's left is values passed in registers that we need to
   736  				// create space for the values.
   737  				v.flag |= flagIndir
   738  				v.ptr = unsafe_New(typ)
   739  				for _, st := range steps {
   740  					switch st.kind {
   741  					case abiStepIntReg:
   742  						offset := add(v.ptr, st.offset, "precomputed value offset")
   743  						intFromReg(regs, st.ireg, st.size, offset)
   744  					case abiStepPointer:
   745  						s := add(v.ptr, st.offset, "precomputed value offset")
   746  						*((*unsafe.Pointer)(s)) = regs.Ptrs[st.ireg]
   747  					case abiStepFloatReg:
   748  						offset := add(v.ptr, st.offset, "precomputed value offset")
   749  						floatFromReg(regs, st.freg, st.size, offset)
   750  					case abiStepStack:
   751  						panic("register-based return value has stack component")
   752  					default:
   753  						panic("unknown ABI part kind")
   754  					}
   755  				}
   756  			} else {
   757  				// Pointer-valued data gets put directly
   758  				// into v.ptr.
   759  				if steps[0].kind != abiStepPointer {
   760  					print("kind=", steps[0].kind, ", type=", typ.String(), "\n")
   761  					panic("mismatch between ABI description and types")
   762  				}
   763  				v.ptr = regs.Ptrs[steps[0].ireg]
   764  			}
   765  		}
   766  		in = append(in, v)
   767  	}
   768  
   769  	// Call underlying function.
   770  	out := f(in)
   771  	numOut := ftyp.NumOut()
   772  	if len(out) != numOut {
   773  		panic("reflect: wrong return count from function created by MakeFunc")
   774  	}
   775  
   776  	// Copy results back into argument frame and register space.
   777  	if numOut > 0 {
   778  		for i, typ := range ftyp.out() {
   779  			v := out[i]
   780  			if v.typ == nil {
   781  				panic("reflect: function created by MakeFunc using " + funcName(f) +
   782  					" returned zero Value")
   783  			}
   784  			if v.flag&flagRO != 0 {
   785  				panic("reflect: function created by MakeFunc using " + funcName(f) +
   786  					" returned value obtained from unexported field")
   787  			}
   788  			if typ.size == 0 {
   789  				continue
   790  			}
   791  
   792  			// Convert v to type typ if v is assignable to a variable
   793  			// of type t in the language spec.
   794  			// See issue 28761.
   795  			//
   796  			//
   797  			// TODO(mknyszek): In the switch to the register ABI we lost
   798  			// the scratch space here for the register cases (and
   799  			// temporarily for all the cases).
   800  			//
   801  			// If/when this happens, take note of the following:
   802  			//
   803  			// We must clear the destination before calling assignTo,
   804  			// in case assignTo writes (with memory barriers) to the
   805  			// target location used as scratch space. See issue 39541.
   806  			v = v.assignTo("reflect.MakeFunc", typ, nil)
   807  		stepsLoop:
   808  			for _, st := range abid.ret.stepsForValue(i) {
   809  				switch st.kind {
   810  				case abiStepStack:
   811  					// Copy values to the "stack."
   812  					addr := add(ptr, st.stkOff, "precomputed stack arg offset")
   813  					// Do not use write barriers. The stack space used
   814  					// for this call is not adequately zeroed, and we
   815  					// are careful to keep the arguments alive until we
   816  					// return to makeFuncStub's caller.
   817  					if v.flag&flagIndir != 0 {
   818  						memmove(addr, v.ptr, st.size)
   819  					} else {
   820  						// This case must be a pointer type.
   821  						*(*uintptr)(addr) = uintptr(v.ptr)
   822  					}
   823  					// There's only one step for a stack-allocated value.
   824  					break stepsLoop
   825  				case abiStepIntReg, abiStepPointer:
   826  					// Copy values to "integer registers."
   827  					if v.flag&flagIndir != 0 {
   828  						offset := add(v.ptr, st.offset, "precomputed value offset")
   829  						intToReg(regs, st.ireg, st.size, offset)
   830  					} else {
   831  						// Only populate the Ints space on the return path.
   832  						// This is safe because out is kept alive until the
   833  						// end of this function, and the return path through
   834  						// makeFuncStub has no preemption, so these pointers
   835  						// are always visible to the GC.
   836  						regs.Ints[st.ireg] = uintptr(v.ptr)
   837  					}
   838  				case abiStepFloatReg:
   839  					// Copy values to "float registers."
   840  					if v.flag&flagIndir == 0 {
   841  						panic("attempted to copy pointer to FP register")
   842  					}
   843  					offset := add(v.ptr, st.offset, "precomputed value offset")
   844  					floatToReg(regs, st.freg, st.size, offset)
   845  				default:
   846  					panic("unknown ABI part kind")
   847  				}
   848  			}
   849  		}
   850  	}
   851  
   852  	// Announce that the return values are valid.
   853  	// After this point the runtime can depend on the return values being valid.
   854  	*retValid = true
   855  
   856  	// We have to make sure that the out slice lives at least until
   857  	// the runtime knows the return values are valid. Otherwise, the
   858  	// return values might not be scanned by anyone during a GC.
   859  	// (out would be dead, and the return slots not yet alive.)
   860  	runtime.KeepAlive(out)
   861  
   862  	// runtime.getArgInfo expects to be able to find ctxt on the
   863  	// stack when it finds our caller, makeFuncStub. Make sure it
   864  	// doesn't get garbage collected.
   865  	runtime.KeepAlive(ctxt)
   866  }
   867  
   868  // methodReceiver returns information about the receiver
   869  // described by v. The Value v may or may not have the
   870  // flagMethod bit set, so the kind cached in v.flag should
   871  // not be used.
   872  // The return value rcvrtype gives the method's actual receiver type.
   873  // The return value t gives the method type signature (without the receiver).
   874  // The return value fn is a pointer to the method code.
   875  func methodReceiver(op string, v Value, methodIndex int) (rcvrtype *rtype, t *funcType, fn unsafe.Pointer) {
   876  	i := methodIndex
   877  	if v.typ.Kind() == Interface {
   878  		tt := (*interfaceType)(unsafe.Pointer(v.typ))
   879  		if uint(i) >= uint(len(tt.methods)) {
   880  			panic("reflect: internal error: invalid method index")
   881  		}
   882  		m := &tt.methods[i]
   883  		if !tt.nameOff(m.name).isExported() {
   884  			panic("reflect: " + op + " of unexported method")
   885  		}
   886  		iface := (*nonEmptyInterface)(v.ptr)
   887  		if iface.itab == nil {
   888  			panic("reflect: " + op + " of method on nil interface value")
   889  		}
   890  		rcvrtype = iface.itab.typ
   891  		fn = unsafe.Pointer(&iface.itab.fun[i])
   892  		t = (*funcType)(unsafe.Pointer(tt.typeOff(m.typ)))
   893  	} else {
   894  		rcvrtype = v.typ
   895  		ms := v.typ.exportedMethods()
   896  		if uint(i) >= uint(len(ms)) {
   897  			panic("reflect: internal error: invalid method index")
   898  		}
   899  		m := ms[i]
   900  		if !v.typ.nameOff(m.name).isExported() {
   901  			panic("reflect: " + op + " of unexported method")
   902  		}
   903  		ifn := v.typ.textOff(m.ifn)
   904  		fn = unsafe.Pointer(&ifn)
   905  		t = (*funcType)(unsafe.Pointer(v.typ.typeOff(m.mtyp)))
   906  	}
   907  	return
   908  }
   909  
   910  // v is a method receiver. Store at p the word which is used to
   911  // encode that receiver at the start of the argument list.
   912  // Reflect uses the "interface" calling convention for
   913  // methods, which always uses one word to record the receiver.
   914  func storeRcvr(v Value, p unsafe.Pointer) {
   915  	t := v.typ
   916  	if t.Kind() == Interface {
   917  		// the interface data word becomes the receiver word
   918  		iface := (*nonEmptyInterface)(v.ptr)
   919  		*(*unsafe.Pointer)(p) = iface.word
   920  	} else if v.flag&flagIndir != 0 && !ifaceIndir(t) {
   921  		*(*unsafe.Pointer)(p) = *(*unsafe.Pointer)(v.ptr)
   922  	} else {
   923  		*(*unsafe.Pointer)(p) = v.ptr
   924  	}
   925  }
   926  
   927  // align returns the result of rounding x up to a multiple of n.
   928  // n must be a power of two.
   929  func align(x, n uintptr) uintptr {
   930  	return (x + n - 1) &^ (n - 1)
   931  }
   932  
   933  // callMethod is the call implementation used by a function returned
   934  // by makeMethodValue (used by v.Method(i).Interface()).
   935  // It is a streamlined version of the usual reflect call: the caller has
   936  // already laid out the argument frame for us, so we don't have
   937  // to deal with individual Values for each argument.
   938  // It is in this file so that it can be next to the two similar functions above.
   939  // The remainder of the makeMethodValue implementation is in makefunc.go.
   940  //
   941  // NOTE: This function must be marked as a "wrapper" in the generated code,
   942  // so that the linker can make it work correctly for panic and recover.
   943  // The gc compilers know to do that for the name "reflect.callMethod".
   944  //
   945  // ctxt is the "closure" generated by makeVethodValue.
   946  // frame is a pointer to the arguments to that closure on the stack.
   947  // retValid points to a boolean which should be set when the results
   948  // section of frame is set.
   949  //
   950  // regs contains the argument values passed in registers and will contain
   951  // the values returned from ctxt.fn in registers.
   952  func callMethod(ctxt *methodValue, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) {
   953  	rcvr := ctxt.rcvr
   954  	rcvrType, valueFuncType, methodFn := methodReceiver("call", rcvr, ctxt.method)
   955  
   956  	// There are two ABIs at play here.
   957  	//
   958  	// methodValueCall was invoked with the ABI assuming there was no
   959  	// receiver ("value ABI") and that's what frame and regs are holding.
   960  	//
   961  	// Meanwhile, we need to actually call the method with a receiver, which
   962  	// has its own ABI ("method ABI"). Everything that follows is a translation
   963  	// between the two.
   964  	_, _, valueABI := funcLayout(valueFuncType, nil)
   965  	valueFrame, valueRegs := frame, regs
   966  	methodFrameType, methodFramePool, methodABI := funcLayout(valueFuncType, rcvrType)
   967  
   968  	// Make a new frame that is one word bigger so we can store the receiver.
   969  	// This space is used for both arguments and return values.
   970  	methodFrame := methodFramePool.Get().(unsafe.Pointer)
   971  	var methodRegs abi.RegArgs
   972  
   973  	// Deal with the receiver. It's guaranteed to only be one word in size.
   974  	switch st := methodABI.call.steps[0]; st.kind {
   975  	case abiStepStack:
   976  		// Only copy the receiver to the stack if the ABI says so.
   977  		// Otherwise, it'll be in a register already.
   978  		storeRcvr(rcvr, methodFrame)
   979  	case abiStepPointer:
   980  		// Put the receiver in a register.
   981  		storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ptrs[st.ireg]))
   982  		fallthrough
   983  	case abiStepIntReg:
   984  		storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ints[st.ireg]))
   985  	case abiStepFloatReg:
   986  		storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Floats[st.freg]))
   987  	default:
   988  		panic("unknown ABI parameter kind")
   989  	}
   990  
   991  	// Translate the rest of the arguments.
   992  	for i, t := range valueFuncType.in() {
   993  		valueSteps := valueABI.call.stepsForValue(i)
   994  		methodSteps := methodABI.call.stepsForValue(i + 1)
   995  
   996  		// Zero-sized types are trivial: nothing to do.
   997  		if len(valueSteps) == 0 {
   998  			if len(methodSteps) != 0 {
   999  				panic("method ABI and value ABI do not align")
  1000  			}
  1001  			continue
  1002  		}
  1003  
  1004  		// There are four cases to handle in translating each
  1005  		// argument:
  1006  		// 1. Stack -> stack translation.
  1007  		// 2. Stack -> registers translation.
  1008  		// 3. Registers -> stack translation.
  1009  		// 4. Registers -> registers translation.
  1010  
  1011  		// If the value ABI passes the value on the stack,
  1012  		// then the method ABI does too, because it has strictly
  1013  		// fewer arguments. Simply copy between the two.
  1014  		if vStep := valueSteps[0]; vStep.kind == abiStepStack {
  1015  			mStep := methodSteps[0]
  1016  			// Handle stack -> stack translation.
  1017  			if mStep.kind == abiStepStack {
  1018  				if vStep.size != mStep.size {
  1019  					panic("method ABI and value ABI do not align")
  1020  				}
  1021  				typedmemmove(t,
  1022  					add(methodFrame, mStep.stkOff, "precomputed stack offset"),
  1023  					add(valueFrame, vStep.stkOff, "precomputed stack offset"))
  1024  				continue
  1025  			}
  1026  			// Handle stack -> register translation.
  1027  			for _, mStep := range methodSteps {
  1028  				from := add(valueFrame, vStep.stkOff+mStep.offset, "precomputed stack offset")
  1029  				switch mStep.kind {
  1030  				case abiStepPointer:
  1031  					// Do the pointer copy directly so we get a write barrier.
  1032  					methodRegs.Ptrs[mStep.ireg] = *(*unsafe.Pointer)(from)
  1033  					fallthrough // We need to make sure this ends up in Ints, too.
  1034  				case abiStepIntReg:
  1035  					intToReg(&methodRegs, mStep.ireg, mStep.size, from)
  1036  				case abiStepFloatReg:
  1037  					floatToReg(&methodRegs, mStep.freg, mStep.size, from)
  1038  				default:
  1039  					panic("unexpected method step")
  1040  				}
  1041  			}
  1042  			continue
  1043  		}
  1044  		// Handle register -> stack translation.
  1045  		if mStep := methodSteps[0]; mStep.kind == abiStepStack {
  1046  			for _, vStep := range valueSteps {
  1047  				to := add(methodFrame, mStep.stkOff+vStep.offset, "precomputed stack offset")
  1048  				switch vStep.kind {
  1049  				case abiStepPointer:
  1050  					// Do the pointer copy directly so we get a write barrier.
  1051  					*(*unsafe.Pointer)(to) = valueRegs.Ptrs[vStep.ireg]
  1052  				case abiStepIntReg:
  1053  					intFromReg(valueRegs, vStep.ireg, vStep.size, to)
  1054  				case abiStepFloatReg:
  1055  					floatFromReg(valueRegs, vStep.freg, vStep.size, to)
  1056  				default:
  1057  					panic("unexpected value step")
  1058  				}
  1059  			}
  1060  			continue
  1061  		}
  1062  		// Handle register -> register translation.
  1063  		if len(valueSteps) != len(methodSteps) {
  1064  			// Because it's the same type for the value, and it's assigned
  1065  			// to registers both times, it should always take up the same
  1066  			// number of registers for each ABI.
  1067  			panic("method ABI and value ABI don't align")
  1068  		}
  1069  		for i, vStep := range valueSteps {
  1070  			mStep := methodSteps[i]
  1071  			if mStep.kind != vStep.kind {
  1072  				panic("method ABI and value ABI don't align")
  1073  			}
  1074  			switch vStep.kind {
  1075  			case abiStepPointer:
  1076  				// Copy this too, so we get a write barrier.
  1077  				methodRegs.Ptrs[mStep.ireg] = valueRegs.Ptrs[vStep.ireg]
  1078  				fallthrough
  1079  			case abiStepIntReg:
  1080  				methodRegs.Ints[mStep.ireg] = valueRegs.Ints[vStep.ireg]
  1081  			case abiStepFloatReg:
  1082  				methodRegs.Floats[mStep.freg] = valueRegs.Floats[vStep.freg]
  1083  			default:
  1084  				panic("unexpected value step")
  1085  			}
  1086  		}
  1087  	}
  1088  
  1089  	methodFrameSize := methodFrameType.size
  1090  	// TODO(mknyszek): Remove this when we no longer have
  1091  	// caller reserved spill space.
  1092  	methodFrameSize = align(methodFrameSize, goarch.PtrSize)
  1093  	methodFrameSize += methodABI.spill
  1094  
  1095  	// Mark pointers in registers for the return path.
  1096  	methodRegs.ReturnIsPtr = methodABI.outRegPtrs
  1097  
  1098  	// Call.
  1099  	// Call copies the arguments from scratch to the stack, calls fn,
  1100  	// and then copies the results back into scratch.
  1101  	call(methodFrameType, methodFn, methodFrame, uint32(methodFrameType.size), uint32(methodABI.retOffset), uint32(methodFrameSize), &methodRegs)
  1102  
  1103  	// Copy return values.
  1104  	//
  1105  	// This is somewhat simpler because both ABIs have an identical
  1106  	// return value ABI (the types are identical). As a result, register
  1107  	// results can simply be copied over. Stack-allocated values are laid
  1108  	// out the same, but are at different offsets from the start of the frame
  1109  	// Ignore any changes to args.
  1110  	// Avoid constructing out-of-bounds pointers if there are no return values.
  1111  	// because the arguments may be laid out differently.
  1112  	if valueRegs != nil {
  1113  		*valueRegs = methodRegs
  1114  	}
  1115  	if retSize := methodFrameType.size - methodABI.retOffset; retSize > 0 {
  1116  		valueRet := add(valueFrame, valueABI.retOffset, "valueFrame's size > retOffset")
  1117  		methodRet := add(methodFrame, methodABI.retOffset, "methodFrame's size > retOffset")
  1118  		// This copies to the stack. Write barriers are not needed.
  1119  		memmove(valueRet, methodRet, retSize)
  1120  	}
  1121  
  1122  	// Tell the runtime it can now depend on the return values
  1123  	// being properly initialized.
  1124  	*retValid = true
  1125  
  1126  	// Clear the scratch space and put it back in the pool.
  1127  	// This must happen after the statement above, so that the return
  1128  	// values will always be scanned by someone.
  1129  	typedmemclr(methodFrameType, methodFrame)
  1130  	methodFramePool.Put(methodFrame)
  1131  
  1132  	// See the comment in callReflect.
  1133  	runtime.KeepAlive(ctxt)
  1134  
  1135  	// Keep valueRegs alive because it may hold live pointer results.
  1136  	// The caller (methodValueCall) has it as a stack object, which is only
  1137  	// scanned when there is a reference to it.
  1138  	runtime.KeepAlive(valueRegs)
  1139  }
  1140  
  1141  // funcName returns the name of f, for use in error messages.
  1142  func funcName(f func([]Value) []Value) string {
  1143  	pc := *(*uintptr)(unsafe.Pointer(&f))
  1144  	rf := runtime.FuncForPC(pc)
  1145  	if rf != nil {
  1146  		return rf.Name()
  1147  	}
  1148  	return "closure"
  1149  }
  1150  
  1151  // Cap returns v's capacity.
  1152  // It panics if v's Kind is not Array, Chan, Slice or pointer to Array.
  1153  func (v Value) Cap() int {
  1154  	// capNonSlice is split out to keep Cap inlineable for slice kinds.
  1155  	if v.kind() == Slice {
  1156  		return (*unsafeheader.Slice)(v.ptr).Cap
  1157  	}
  1158  	return v.capNonSlice()
  1159  }
  1160  
  1161  func (v Value) capNonSlice() int {
  1162  	k := v.kind()
  1163  	switch k {
  1164  	case Array:
  1165  		return v.typ.Len()
  1166  	case Chan:
  1167  		return chancap(v.pointer())
  1168  	case Ptr:
  1169  		if v.typ.Elem().Kind() == Array {
  1170  			return v.typ.Elem().Len()
  1171  		}
  1172  		panic("reflect: call of reflect.Value.Cap on ptr to non-array Value")
  1173  	}
  1174  	panic(&ValueError{"reflect.Value.Cap", v.kind()})
  1175  }
  1176  
  1177  // Close closes the channel v.
  1178  // It panics if v's Kind is not Chan.
  1179  func (v Value) Close() {
  1180  	v.mustBe(Chan)
  1181  	v.mustBeExported()
  1182  	chanclose(v.pointer())
  1183  }
  1184  
  1185  // CanComplex reports whether Complex can be used without panicking.
  1186  func (v Value) CanComplex() bool {
  1187  	switch v.kind() {
  1188  	case Complex64, Complex128:
  1189  		return true
  1190  	default:
  1191  		return false
  1192  	}
  1193  }
  1194  
  1195  // Complex returns v's underlying value, as a complex128.
  1196  // It panics if v's Kind is not Complex64 or Complex128
  1197  func (v Value) Complex() complex128 {
  1198  	k := v.kind()
  1199  	switch k {
  1200  	case Complex64:
  1201  		return complex128(*(*complex64)(v.ptr))
  1202  	case Complex128:
  1203  		return *(*complex128)(v.ptr)
  1204  	}
  1205  	panic(&ValueError{"reflect.Value.Complex", v.kind()})
  1206  }
  1207  
  1208  // Elem returns the value that the interface v contains
  1209  // or that the pointer v points to.
  1210  // It panics if v's Kind is not Interface or Pointer.
  1211  // It returns the zero Value if v is nil.
  1212  func (v Value) Elem() Value {
  1213  	k := v.kind()
  1214  	switch k {
  1215  	case Interface:
  1216  		var eface any
  1217  		if v.typ.NumMethod() == 0 {
  1218  			eface = *(*any)(v.ptr)
  1219  		} else {
  1220  			eface = (any)(*(*interface {
  1221  				M()
  1222  			})(v.ptr))
  1223  		}
  1224  		x := unpackEface(eface)
  1225  		if x.flag != 0 {
  1226  			x.flag |= v.flag.ro()
  1227  		}
  1228  		return x
  1229  	case Pointer:
  1230  		ptr := v.ptr
  1231  		if v.flag&flagIndir != 0 {
  1232  			if ifaceIndir(v.typ) {
  1233  				// This is a pointer to a not-in-heap object. ptr points to a uintptr
  1234  				// in the heap. That uintptr is the address of a not-in-heap object.
  1235  				// In general, pointers to not-in-heap objects can be total junk.
  1236  				// But Elem() is asking to dereference it, so the user has asserted
  1237  				// that at least it is a valid pointer (not just an integer stored in
  1238  				// a pointer slot). So let's check, to make sure that it isn't a pointer
  1239  				// that the runtime will crash on if it sees it during GC or write barriers.
  1240  				// Since it is a not-in-heap pointer, all pointers to the heap are
  1241  				// forbidden! That makes the test pretty easy.
  1242  				// See issue 48399.
  1243  				if !verifyNotInHeapPtr(*(*uintptr)(ptr)) {
  1244  					panic("reflect: reflect.Value.Elem on an invalid notinheap pointer")
  1245  				}
  1246  			}
  1247  			ptr = *(*unsafe.Pointer)(ptr)
  1248  		}
  1249  		// The returned value's address is v's value.
  1250  		if ptr == nil {
  1251  			return Value{}
  1252  		}
  1253  		tt := (*ptrType)(unsafe.Pointer(v.typ))
  1254  		typ := tt.elem
  1255  		fl := v.flag&flagRO | flagIndir | flagAddr
  1256  		fl |= flag(typ.Kind())
  1257  		return Value{typ, ptr, fl}
  1258  	}
  1259  	panic(&ValueError{"reflect.Value.Elem", v.kind()})
  1260  }
  1261  
  1262  // Field returns the i'th field of the struct v.
  1263  // It panics if v's Kind is not Struct or i is out of range.
  1264  func (v Value) Field(i int) Value {
  1265  	if v.kind() != Struct {
  1266  		panic(&ValueError{"reflect.Value.Field", v.kind()})
  1267  	}
  1268  	tt := (*structType)(unsafe.Pointer(v.typ))
  1269  	if uint(i) >= uint(len(tt.fields)) {
  1270  		panic("reflect: Field index out of range")
  1271  	}
  1272  	field := &tt.fields[i]
  1273  	typ := field.typ
  1274  
  1275  	// Inherit permission bits from v, but clear flagEmbedRO.
  1276  	fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
  1277  	// Using an unexported field forces flagRO.
  1278  	if !field.name.isExported() {
  1279  		if field.embedded() {
  1280  			fl |= flagEmbedRO
  1281  		} else {
  1282  			fl |= flagStickyRO
  1283  		}
  1284  	}
  1285  	// Either flagIndir is set and v.ptr points at struct,
  1286  	// or flagIndir is not set and v.ptr is the actual struct data.
  1287  	// In the former case, we want v.ptr + offset.
  1288  	// In the latter case, we must have field.offset = 0,
  1289  	// so v.ptr + field.offset is still the correct address.
  1290  	ptr := add(v.ptr, field.offset, "same as non-reflect &v.field")
  1291  	return Value{typ, ptr, fl}
  1292  }
  1293  
  1294  // FieldByIndex returns the nested field corresponding to index.
  1295  // It panics if evaluation requires stepping through a nil
  1296  // pointer or a field that is not a struct.
  1297  func (v Value) FieldByIndex(index []int) Value {
  1298  	if len(index) == 1 {
  1299  		return v.Field(index[0])
  1300  	}
  1301  	v.mustBe(Struct)
  1302  	for i, x := range index {
  1303  		if i > 0 {
  1304  			if v.Kind() == Pointer && v.typ.Elem().Kind() == Struct {
  1305  				if v.IsNil() {
  1306  					panic("reflect: indirection through nil pointer to embedded struct")
  1307  				}
  1308  				v = v.Elem()
  1309  			}
  1310  		}
  1311  		v = v.Field(x)
  1312  	}
  1313  	return v
  1314  }
  1315  
  1316  // FieldByIndexErr returns the nested field corresponding to index.
  1317  // It returns an error if evaluation requires stepping through a nil
  1318  // pointer, but panics if it must step through a field that
  1319  // is not a struct.
  1320  func (v Value) FieldByIndexErr(index []int) (Value, error) {
  1321  	if len(index) == 1 {
  1322  		return v.Field(index[0]), nil
  1323  	}
  1324  	v.mustBe(Struct)
  1325  	for i, x := range index {
  1326  		if i > 0 {
  1327  			if v.Kind() == Ptr && v.typ.Elem().Kind() == Struct {
  1328  				if v.IsNil() {
  1329  					return Value{}, errors.New("reflect: indirection through nil pointer to embedded struct field " + v.typ.Elem().Name())
  1330  				}
  1331  				v = v.Elem()
  1332  			}
  1333  		}
  1334  		v = v.Field(x)
  1335  	}
  1336  	return v, nil
  1337  }
  1338  
  1339  // FieldByName returns the struct field with the given name.
  1340  // It returns the zero Value if no field was found.
  1341  // It panics if v's Kind is not struct.
  1342  func (v Value) FieldByName(name string) Value {
  1343  	v.mustBe(Struct)
  1344  	if f, ok := v.typ.FieldByName(name); ok {
  1345  		return v.FieldByIndex(f.Index)
  1346  	}
  1347  	return Value{}
  1348  }
  1349  
  1350  // FieldByNameFunc returns the struct field with a name
  1351  // that satisfies the match function.
  1352  // It panics if v's Kind is not struct.
  1353  // It returns the zero Value if no field was found.
  1354  func (v Value) FieldByNameFunc(match func(string) bool) Value {
  1355  	if f, ok := v.typ.FieldByNameFunc(match); ok {
  1356  		return v.FieldByIndex(f.Index)
  1357  	}
  1358  	return Value{}
  1359  }
  1360  
  1361  // CanFloat reports whether Float can be used without panicking.
  1362  func (v Value) CanFloat() bool {
  1363  	switch v.kind() {
  1364  	case Float32, Float64:
  1365  		return true
  1366  	default:
  1367  		return false
  1368  	}
  1369  }
  1370  
  1371  // Float returns v's underlying value, as a float64.
  1372  // It panics if v's Kind is not Float32 or Float64
  1373  func (v Value) Float() float64 {
  1374  	k := v.kind()
  1375  	switch k {
  1376  	case Float32:
  1377  		return float64(*(*float32)(v.ptr))
  1378  	case Float64:
  1379  		return *(*float64)(v.ptr)
  1380  	}
  1381  	panic(&ValueError{"reflect.Value.Float", v.kind()})
  1382  }
  1383  
  1384  var uint8Type = TypeOf(uint8(0)).(*rtype)
  1385  
  1386  // Index returns v's i'th element.
  1387  // It panics if v's Kind is not Array, Slice, or String or i is out of range.
  1388  func (v Value) Index(i int) Value {
  1389  	switch v.kind() {
  1390  	case Array:
  1391  		tt := (*arrayType)(unsafe.Pointer(v.typ))
  1392  		if uint(i) >= uint(tt.len) {
  1393  			panic("reflect: array index out of range")
  1394  		}
  1395  		typ := tt.elem
  1396  		offset := uintptr(i) * typ.size
  1397  
  1398  		// Either flagIndir is set and v.ptr points at array,
  1399  		// or flagIndir is not set and v.ptr is the actual array data.
  1400  		// In the former case, we want v.ptr + offset.
  1401  		// In the latter case, we must be doing Index(0), so offset = 0,
  1402  		// so v.ptr + offset is still the correct address.
  1403  		val := add(v.ptr, offset, "same as &v[i], i < tt.len")
  1404  		fl := v.flag&(flagIndir|flagAddr) | v.flag.ro() | flag(typ.Kind()) // bits same as overall array
  1405  		return Value{typ, val, fl}
  1406  
  1407  	case Slice:
  1408  		// Element flag same as Elem of Pointer.
  1409  		// Addressable, indirect, possibly read-only.
  1410  		s := (*unsafeheader.Slice)(v.ptr)
  1411  		if uint(i) >= uint(s.Len) {
  1412  			panic("reflect: slice index out of range")
  1413  		}
  1414  		tt := (*sliceType)(unsafe.Pointer(v.typ))
  1415  		typ := tt.elem
  1416  		val := arrayAt(s.Data, i, typ.size, "i < s.Len")
  1417  		fl := flagAddr | flagIndir | v.flag.ro() | flag(typ.Kind())
  1418  		return Value{typ, val, fl}
  1419  
  1420  	case String:
  1421  		s := (*unsafeheader.String)(v.ptr)
  1422  		if uint(i) >= uint(s.Len) {
  1423  			panic("reflect: string index out of range")
  1424  		}
  1425  		p := arrayAt(s.Data, i, 1, "i < s.Len")
  1426  		fl := v.flag.ro() | flag(Uint8) | flagIndir
  1427  		return Value{uint8Type, p, fl}
  1428  	}
  1429  	panic(&ValueError{"reflect.Value.Index", v.kind()})
  1430  }
  1431  
  1432  // CanInt reports whether Int can be used without panicking.
  1433  func (v Value) CanInt() bool {
  1434  	switch v.kind() {
  1435  	case Int, Int8, Int16, Int32, Int64:
  1436  		return true
  1437  	default:
  1438  		return false
  1439  	}
  1440  }
  1441  
  1442  // Int returns v's underlying value, as an int64.
  1443  // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
  1444  func (v Value) Int() int64 {
  1445  	k := v.kind()
  1446  	p := v.ptr
  1447  	switch k {
  1448  	case Int:
  1449  		return int64(*(*int)(p))
  1450  	case Int8:
  1451  		return int64(*(*int8)(p))
  1452  	case Int16:
  1453  		return int64(*(*int16)(p))
  1454  	case Int32:
  1455  		return int64(*(*int32)(p))
  1456  	case Int64:
  1457  		return *(*int64)(p)
  1458  	}
  1459  	panic(&ValueError{"reflect.Value.Int", v.kind()})
  1460  }
  1461  
  1462  // CanInterface reports whether Interface can be used without panicking.
  1463  func (v Value) CanInterface() bool {
  1464  	if v.flag == 0 {
  1465  		panic(&ValueError{"reflect.Value.CanInterface", Invalid})
  1466  	}
  1467  	return v.flag&flagRO == 0
  1468  }
  1469  
  1470  // Interface returns v's current value as an interface{}.
  1471  // It is equivalent to:
  1472  //
  1473  //	var i interface{} = (v's underlying value)
  1474  //
  1475  // It panics if the Value was obtained by accessing
  1476  // unexported struct fields.
  1477  func (v Value) Interface() (i any) {
  1478  	return valueInterface(v, true)
  1479  }
  1480  
  1481  func valueInterface(v Value, safe bool) any {
  1482  	if v.flag == 0 {
  1483  		panic(&ValueError{"reflect.Value.Interface", Invalid})
  1484  	}
  1485  	if safe && v.flag&flagRO != 0 {
  1486  		// Do not allow access to unexported values via Interface,
  1487  		// because they might be pointers that should not be
  1488  		// writable or methods or function that should not be callable.
  1489  		panic("reflect.Value.Interface: cannot return value obtained from unexported field or method")
  1490  	}
  1491  	if v.flag&flagMethod != 0 {
  1492  		v = makeMethodValue("Interface", v)
  1493  	}
  1494  
  1495  	if v.kind() == Interface {
  1496  		// Special case: return the element inside the interface.
  1497  		// Empty interface has one layout, all interfaces with
  1498  		// methods have a second layout.
  1499  		if v.NumMethod() == 0 {
  1500  			return *(*any)(v.ptr)
  1501  		}
  1502  		return *(*interface {
  1503  			M()
  1504  		})(v.ptr)
  1505  	}
  1506  
  1507  	// TODO: pass safe to packEface so we don't need to copy if safe==true?
  1508  	return packEface(v)
  1509  }
  1510  
  1511  // InterfaceData returns a pair of unspecified uintptr values.
  1512  // It panics if v's Kind is not Interface.
  1513  //
  1514  // In earlier versions of Go, this function returned the interface's
  1515  // value as a uintptr pair. As of Go 1.4, the implementation of
  1516  // interface values precludes any defined use of InterfaceData.
  1517  //
  1518  // Deprecated: The memory representation of interface values is not
  1519  // compatible with InterfaceData.
  1520  func (v Value) InterfaceData() [2]uintptr {
  1521  	v.mustBe(Interface)
  1522  	// We treat this as a read operation, so we allow
  1523  	// it even for unexported data, because the caller
  1524  	// has to import "unsafe" to turn it into something
  1525  	// that can be abused.
  1526  	// Interface value is always bigger than a word; assume flagIndir.
  1527  	return *(*[2]uintptr)(v.ptr)
  1528  }
  1529  
  1530  // IsNil reports whether its argument v is nil. The argument must be
  1531  // a chan, func, interface, map, pointer, or slice value; if it is
  1532  // not, IsNil panics. Note that IsNil is not always equivalent to a
  1533  // regular comparison with nil in Go. For example, if v was created
  1534  // by calling ValueOf with an uninitialized interface variable i,
  1535  // i==nil will be true but v.IsNil will panic as v will be the zero
  1536  // Value.
  1537  func (v Value) IsNil() bool {
  1538  	k := v.kind()
  1539  	switch k {
  1540  	case Chan, Func, Map, Pointer, UnsafePointer:
  1541  		if v.flag&flagMethod != 0 {
  1542  			return false
  1543  		}
  1544  		ptr := v.ptr
  1545  		if v.flag&flagIndir != 0 {
  1546  			ptr = *(*unsafe.Pointer)(ptr)
  1547  		}
  1548  		return ptr == nil
  1549  	case Interface, Slice:
  1550  		// Both interface and slice are nil if first word is 0.
  1551  		// Both are always bigger than a word; assume flagIndir.
  1552  		return *(*unsafe.Pointer)(v.ptr) == nil
  1553  	}
  1554  	panic(&ValueError{"reflect.Value.IsNil", v.kind()})
  1555  }
  1556  
  1557  // IsValid reports whether v represents a value.
  1558  // It returns false if v is the zero Value.
  1559  // If IsValid returns false, all other methods except String panic.
  1560  // Most functions and methods never return an invalid Value.
  1561  // If one does, its documentation states the conditions explicitly.
  1562  func (v Value) IsValid() bool {
  1563  	return v.flag != 0
  1564  }
  1565  
  1566  // IsZero reports whether v is the zero value for its type.
  1567  // It panics if the argument is invalid.
  1568  func (v Value) IsZero() bool {
  1569  	switch v.kind() {
  1570  	case Bool:
  1571  		return !v.Bool()
  1572  	case Int, Int8, Int16, Int32, Int64:
  1573  		return v.Int() == 0
  1574  	case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  1575  		return v.Uint() == 0
  1576  	case Float32, Float64:
  1577  		return math.Float64bits(v.Float()) == 0
  1578  	case Complex64, Complex128:
  1579  		c := v.Complex()
  1580  		return math.Float64bits(real(c)) == 0 && math.Float64bits(imag(c)) == 0
  1581  	case Array:
  1582  		for i := 0; i < v.Len(); i++ {
  1583  			if !v.Index(i).IsZero() {
  1584  				return false
  1585  			}
  1586  		}
  1587  		return true
  1588  	case Chan, Func, Interface, Map, Pointer, Slice, UnsafePointer:
  1589  		return v.IsNil()
  1590  	case String:
  1591  		return v.Len() == 0
  1592  	case Struct:
  1593  		for i := 0; i < v.NumField(); i++ {
  1594  			if !v.Field(i).IsZero() {
  1595  				return false
  1596  			}
  1597  		}
  1598  		return true
  1599  	default:
  1600  		// This should never happens, but will act as a safeguard for
  1601  		// later, as a default value doesn't makes sense here.
  1602  		panic(&ValueError{"reflect.Value.IsZero", v.Kind()})
  1603  	}
  1604  }
  1605  
  1606  // Kind returns v's Kind.
  1607  // If v is the zero Value (IsValid returns false), Kind returns Invalid.
  1608  func (v Value) Kind() Kind {
  1609  	return v.kind()
  1610  }
  1611  
  1612  // Len returns v's length.
  1613  // It panics if v's Kind is not Array, Chan, Map, Slice, String, or pointer to Array.
  1614  func (v Value) Len() int {
  1615  	// lenNonSlice is split out to keep Len inlineable for slice kinds.
  1616  	if v.kind() == Slice {
  1617  		return (*unsafeheader.Slice)(v.ptr).Len
  1618  	}
  1619  	return v.lenNonSlice()
  1620  }
  1621  
  1622  func (v Value) lenNonSlice() int {
  1623  	switch k := v.kind(); k {
  1624  	case Array:
  1625  		tt := (*arrayType)(unsafe.Pointer(v.typ))
  1626  		return int(tt.len)
  1627  	case Chan:
  1628  		return chanlen(v.pointer())
  1629  	case Map:
  1630  		return maplen(v.pointer())
  1631  	case String:
  1632  		// String is bigger than a word; assume flagIndir.
  1633  		return (*unsafeheader.String)(v.ptr).Len
  1634  	case Ptr:
  1635  		if v.typ.Elem().Kind() == Array {
  1636  			return v.typ.Elem().Len()
  1637  		}
  1638  		panic("reflect: call of reflect.Value.Len on ptr to non-array Value")
  1639  	}
  1640  	panic(&ValueError{"reflect.Value.Len", v.kind()})
  1641  }
  1642  
  1643  var stringType = TypeOf("").(*rtype)
  1644  
  1645  // MapIndex returns the value associated with key in the map v.
  1646  // It panics if v's Kind is not Map.
  1647  // It returns the zero Value if key is not found in the map or if v represents a nil map.
  1648  // As in Go, the key's value must be assignable to the map's key type.
  1649  func (v Value) MapIndex(key Value) Value {
  1650  	v.mustBe(Map)
  1651  	tt := (*mapType)(unsafe.Pointer(v.typ))
  1652  
  1653  	// Do not require key to be exported, so that DeepEqual
  1654  	// and other programs can use all the keys returned by
  1655  	// MapKeys as arguments to MapIndex. If either the map
  1656  	// or the key is unexported, though, the result will be
  1657  	// considered unexported. This is consistent with the
  1658  	// behavior for structs, which allow read but not write
  1659  	// of unexported fields.
  1660  
  1661  	var e unsafe.Pointer
  1662  	if (tt.key == stringType || key.kind() == String) && tt.key == key.typ && tt.elem.size <= maxValSize {
  1663  		k := *(*string)(key.ptr)
  1664  		e = mapaccess_faststr(v.typ, v.pointer(), k)
  1665  	} else {
  1666  		key = key.assignTo("reflect.Value.MapIndex", tt.key, nil)
  1667  		var k unsafe.Pointer
  1668  		if key.flag&flagIndir != 0 {
  1669  			k = key.ptr
  1670  		} else {
  1671  			k = unsafe.Pointer(&key.ptr)
  1672  		}
  1673  		e = mapaccess(v.typ, v.pointer(), k)
  1674  	}
  1675  	if e == nil {
  1676  		return Value{}
  1677  	}
  1678  	typ := tt.elem
  1679  	fl := (v.flag | key.flag).ro()
  1680  	fl |= flag(typ.Kind())
  1681  	return copyVal(typ, fl, e)
  1682  }
  1683  
  1684  // MapKeys returns a slice containing all the keys present in the map,
  1685  // in unspecified order.
  1686  // It panics if v's Kind is not Map.
  1687  // It returns an empty slice if v represents a nil map.
  1688  func (v Value) MapKeys() []Value {
  1689  	v.mustBe(Map)
  1690  	tt := (*mapType)(unsafe.Pointer(v.typ))
  1691  	keyType := tt.key
  1692  
  1693  	fl := v.flag.ro() | flag(keyType.Kind())
  1694  
  1695  	m := v.pointer()
  1696  	mlen := int(0)
  1697  	if m != nil {
  1698  		mlen = maplen(m)
  1699  	}
  1700  	var it hiter
  1701  	mapiterinit(v.typ, m, &it)
  1702  	a := make([]Value, mlen)
  1703  	var i int
  1704  	for i = 0; i < len(a); i++ {
  1705  		key := mapiterkey(&it)
  1706  		if key == nil {
  1707  			// Someone deleted an entry from the map since we
  1708  			// called maplen above. It's a data race, but nothing
  1709  			// we can do about it.
  1710  			break
  1711  		}
  1712  		a[i] = copyVal(keyType, fl, key)
  1713  		mapiternext(&it)
  1714  	}
  1715  	return a[:i]
  1716  }
  1717  
  1718  // hiter's structure matches runtime.hiter's structure.
  1719  // Having a clone here allows us to embed a map iterator
  1720  // inside type MapIter so that MapIters can be re-used
  1721  // without doing any allocations.
  1722  type hiter struct {
  1723  	key         unsafe.Pointer
  1724  	elem        unsafe.Pointer
  1725  	t           unsafe.Pointer
  1726  	h           unsafe.Pointer
  1727  	buckets     unsafe.Pointer
  1728  	bptr        unsafe.Pointer
  1729  	overflow    *[]unsafe.Pointer
  1730  	oldoverflow *[]unsafe.Pointer
  1731  	startBucket uintptr
  1732  	offset      uint8
  1733  	wrapped     bool
  1734  	B           uint8
  1735  	i           uint8
  1736  	bucket      uintptr
  1737  	checkBucket uintptr
  1738  }
  1739  
  1740  func (h *hiter) initialized() bool {
  1741  	return h.t != nil
  1742  }
  1743  
  1744  // A MapIter is an iterator for ranging over a map.
  1745  // See Value.MapRange.
  1746  type MapIter struct {
  1747  	m     Value
  1748  	hiter hiter
  1749  }
  1750  
  1751  // Key returns the key of iter's current map entry.
  1752  func (iter *MapIter) Key() Value {
  1753  	if !iter.hiter.initialized() {
  1754  		panic("MapIter.Key called before Next")
  1755  	}
  1756  	iterkey := mapiterkey(&iter.hiter)
  1757  	if iterkey == nil {
  1758  		panic("MapIter.Key called on exhausted iterator")
  1759  	}
  1760  
  1761  	t := (*mapType)(unsafe.Pointer(iter.m.typ))
  1762  	ktype := t.key
  1763  	return copyVal(ktype, iter.m.flag.ro()|flag(ktype.Kind()), iterkey)
  1764  }
  1765  
  1766  // SetIterKey assigns to v the key of iter's current map entry.
  1767  // It is equivalent to v.Set(iter.Key()), but it avoids allocating a new Value.
  1768  // As in Go, the key must be assignable to v's type.
  1769  func (v Value) SetIterKey(iter *MapIter) {
  1770  	if !iter.hiter.initialized() {
  1771  		panic("reflect: Value.SetIterKey called before Next")
  1772  	}
  1773  	iterkey := mapiterkey(&iter.hiter)
  1774  	if iterkey == nil {
  1775  		panic("reflect: Value.SetIterKey called on exhausted iterator")
  1776  	}
  1777  
  1778  	v.mustBeAssignable()
  1779  	var target unsafe.Pointer
  1780  	if v.kind() == Interface {
  1781  		target = v.ptr
  1782  	}
  1783  
  1784  	t := (*mapType)(unsafe.Pointer(iter.m.typ))
  1785  	ktype := t.key
  1786  
  1787  	key := Value{ktype, iterkey, iter.m.flag | flag(ktype.Kind()) | flagIndir}
  1788  	key = key.assignTo("reflect.MapIter.SetKey", v.typ, target)
  1789  	typedmemmove(v.typ, v.ptr, key.ptr)
  1790  }
  1791  
  1792  // Value returns the value of iter's current map entry.
  1793  func (iter *MapIter) Value() Value {
  1794  	if !iter.hiter.initialized() {
  1795  		panic("MapIter.Value called before Next")
  1796  	}
  1797  	iterelem := mapiterelem(&iter.hiter)
  1798  	if iterelem == nil {
  1799  		panic("MapIter.Value called on exhausted iterator")
  1800  	}
  1801  
  1802  	t := (*mapType)(unsafe.Pointer(iter.m.typ))
  1803  	vtype := t.elem
  1804  	return copyVal(vtype, iter.m.flag.ro()|flag(vtype.Kind()), iterelem)
  1805  }
  1806  
  1807  // SetIterValue assigns to v the value of iter's current map entry.
  1808  // It is equivalent to v.Set(iter.Value()), but it avoids allocating a new Value.
  1809  // As in Go, the value must be assignable to v's type.
  1810  func (v Value) SetIterValue(iter *MapIter) {
  1811  	if !iter.hiter.initialized() {
  1812  		panic("reflect: Value.SetIterValue called before Next")
  1813  	}
  1814  	iterelem := mapiterelem(&iter.hiter)
  1815  	if iterelem == nil {
  1816  		panic("reflect: Value.SetIterValue called on exhausted iterator")
  1817  	}
  1818  
  1819  	v.mustBeAssignable()
  1820  	var target unsafe.Pointer
  1821  	if v.kind() == Interface {
  1822  		target = v.ptr
  1823  	}
  1824  
  1825  	t := (*mapType)(unsafe.Pointer(iter.m.typ))
  1826  	vtype := t.elem
  1827  
  1828  	elem := Value{vtype, iterelem, iter.m.flag | flag(vtype.Kind()) | flagIndir}
  1829  	elem = elem.assignTo("reflect.MapIter.SetValue", v.typ, target)
  1830  	typedmemmove(v.typ, v.ptr, elem.ptr)
  1831  }
  1832  
  1833  // Next advances the map iterator and reports whether there is another
  1834  // entry. It returns false when iter is exhausted; subsequent
  1835  // calls to Key, Value, or Next will panic.
  1836  func (iter *MapIter) Next() bool {
  1837  	if !iter.m.IsValid() {
  1838  		panic("MapIter.Next called on an iterator that does not have an associated map Value")
  1839  	}
  1840  	if !iter.hiter.initialized() {
  1841  		mapiterinit(iter.m.typ, iter.m.pointer(), &iter.hiter)
  1842  	} else {
  1843  		if mapiterkey(&iter.hiter) == nil {
  1844  			panic("MapIter.Next called on exhausted iterator")
  1845  		}
  1846  		mapiternext(&iter.hiter)
  1847  	}
  1848  	return mapiterkey(&iter.hiter) != nil
  1849  }
  1850  
  1851  // Reset modifies iter to iterate over v.
  1852  // It panics if v's Kind is not Map and v is not the zero Value.
  1853  // Reset(Value{}) causes iter to not to refer to any map,
  1854  // which may allow the previously iterated-over map to be garbage collected.
  1855  func (iter *MapIter) Reset(v Value) {
  1856  	if v.IsValid() {
  1857  		v.mustBe(Map)
  1858  	}
  1859  	iter.m = v
  1860  	iter.hiter = hiter{}
  1861  }
  1862  
  1863  // MapRange returns a range iterator for a map.
  1864  // It panics if v's Kind is not Map.
  1865  //
  1866  // Call Next to advance the iterator, and Key/Value to access each entry.
  1867  // Next returns false when the iterator is exhausted.
  1868  // MapRange follows the same iteration semantics as a range statement.
  1869  //
  1870  // Example:
  1871  //
  1872  //	iter := reflect.ValueOf(m).MapRange()
  1873  //	for iter.Next() {
  1874  //		k := iter.Key()
  1875  //		v := iter.Value()
  1876  //		...
  1877  //	}
  1878  func (v Value) MapRange() *MapIter {
  1879  	// This is inlinable to take advantage of "function outlining".
  1880  	// The allocation of MapIter can be stack allocated if the caller
  1881  	// does not allow it to escape.
  1882  	// See https://blog.filippo.io/efficient-go-apis-with-the-inliner/
  1883  	if v.kind() != Map {
  1884  		v.panicNotMap()
  1885  	}
  1886  	return &MapIter{m: v}
  1887  }
  1888  
  1889  func (f flag) panicNotMap() {
  1890  	f.mustBe(Map)
  1891  }
  1892  
  1893  // copyVal returns a Value containing the map key or value at ptr,
  1894  // allocating a new variable as needed.
  1895  func copyVal(typ *rtype, fl flag, ptr unsafe.Pointer) Value {
  1896  	if ifaceIndir(typ) {
  1897  		// Copy result so future changes to the map
  1898  		// won't change the underlying value.
  1899  		c := unsafe_New(typ)
  1900  		typedmemmove(typ, c, ptr)
  1901  		return Value{typ, c, fl | flagIndir}
  1902  	}
  1903  	return Value{typ, *(*unsafe.Pointer)(ptr), fl}
  1904  }
  1905  
  1906  // Method returns a function value corresponding to v's i'th method.
  1907  // The arguments to a Call on the returned function should not include
  1908  // a receiver; the returned function will always use v as the receiver.
  1909  // Method panics if i is out of range or if v is a nil interface value.
  1910  func (v Value) Method(i int) Value {
  1911  	if v.typ == nil {
  1912  		panic(&ValueError{"reflect.Value.Method", Invalid})
  1913  	}
  1914  	if v.flag&flagMethod != 0 || uint(i) >= uint(v.typ.NumMethod()) {
  1915  		panic("reflect: Method index out of range")
  1916  	}
  1917  	if v.typ.Kind() == Interface && v.IsNil() {
  1918  		panic("reflect: Method on nil interface value")
  1919  	}
  1920  	fl := v.flag.ro() | (v.flag & flagIndir)
  1921  	fl |= flag(Func)
  1922  	fl |= flag(i)<<flagMethodShift | flagMethod
  1923  	return Value{v.typ, v.ptr, fl}
  1924  }
  1925  
  1926  // NumMethod returns the number of methods in the value's method set.
  1927  //
  1928  // For a non-interface type, it returns the number of exported methods.
  1929  //
  1930  // For an interface type, it returns the number of exported and unexported methods.
  1931  func (v Value) NumMethod() int {
  1932  	if v.typ == nil {
  1933  		panic(&ValueError{"reflect.Value.NumMethod", Invalid})
  1934  	}
  1935  	if v.flag&flagMethod != 0 {
  1936  		return 0
  1937  	}
  1938  	return v.typ.NumMethod()
  1939  }
  1940  
  1941  // MethodByName returns a function value corresponding to the method
  1942  // of v with the given name.
  1943  // The arguments to a Call on the returned function should not include
  1944  // a receiver; the returned function will always use v as the receiver.
  1945  // It returns the zero Value if no method was found.
  1946  func (v Value) MethodByName(name string) Value {
  1947  	if v.typ == nil {
  1948  		panic(&ValueError{"reflect.Value.MethodByName", Invalid})
  1949  	}
  1950  	if v.flag&flagMethod != 0 {
  1951  		return Value{}
  1952  	}
  1953  	m, ok := v.typ.MethodByName(name)
  1954  	if !ok {
  1955  		return Value{}
  1956  	}
  1957  	return v.Method(m.Index)
  1958  }
  1959  
  1960  // NumField returns the number of fields in the struct v.
  1961  // It panics if v's Kind is not Struct.
  1962  func (v Value) NumField() int {
  1963  	v.mustBe(Struct)
  1964  	tt := (*structType)(unsafe.Pointer(v.typ))
  1965  	return len(tt.fields)
  1966  }
  1967  
  1968  // OverflowComplex reports whether the complex128 x cannot be represented by v's type.
  1969  // It panics if v's Kind is not Complex64 or Complex128.
  1970  func (v Value) OverflowComplex(x complex128) bool {
  1971  	k := v.kind()
  1972  	switch k {
  1973  	case Complex64:
  1974  		return overflowFloat32(real(x)) || overflowFloat32(imag(x))
  1975  	case Complex128:
  1976  		return false
  1977  	}
  1978  	panic(&ValueError{"reflect.Value.OverflowComplex", v.kind()})
  1979  }
  1980  
  1981  // OverflowFloat reports whether the float64 x cannot be represented by v's type.
  1982  // It panics if v's Kind is not Float32 or Float64.
  1983  func (v Value) OverflowFloat(x float64) bool {
  1984  	k := v.kind()
  1985  	switch k {
  1986  	case Float32:
  1987  		return overflowFloat32(x)
  1988  	case Float64:
  1989  		return false
  1990  	}
  1991  	panic(&ValueError{"reflect.Value.OverflowFloat", v.kind()})
  1992  }
  1993  
  1994  func overflowFloat32(x float64) bool {
  1995  	if x < 0 {
  1996  		x = -x
  1997  	}
  1998  	return math.MaxFloat32 < x && x <= math.MaxFloat64
  1999  }
  2000  
  2001  // OverflowInt reports whether the int64 x cannot be represented by v's type.
  2002  // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
  2003  func (v Value) OverflowInt(x int64) bool {
  2004  	k := v.kind()
  2005  	switch k {
  2006  	case Int, Int8, Int16, Int32, Int64:
  2007  		bitSize := v.typ.size * 8
  2008  		trunc := (x << (64 - bitSize)) >> (64 - bitSize)
  2009  		return x != trunc
  2010  	}
  2011  	panic(&ValueError{"reflect.Value.OverflowInt", v.kind()})
  2012  }
  2013  
  2014  // OverflowUint reports whether the uint64 x cannot be represented by v's type.
  2015  // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
  2016  func (v Value) OverflowUint(x uint64) bool {
  2017  	k := v.kind()
  2018  	switch k {
  2019  	case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64:
  2020  		bitSize := v.typ.size * 8
  2021  		trunc := (x << (64 - bitSize)) >> (64 - bitSize)
  2022  		return x != trunc
  2023  	}
  2024  	panic(&ValueError{"reflect.Value.OverflowUint", v.kind()})
  2025  }
  2026  
  2027  //go:nocheckptr
  2028  // This prevents inlining Value.Pointer when -d=checkptr is enabled,
  2029  // which ensures cmd/compile can recognize unsafe.Pointer(v.Pointer())
  2030  // and make an exception.
  2031  
  2032  // Pointer returns v's value as a uintptr.
  2033  // It returns uintptr instead of unsafe.Pointer so that
  2034  // code using reflect cannot obtain unsafe.Pointers
  2035  // without importing the unsafe package explicitly.
  2036  // It panics if v's Kind is not Chan, Func, Map, Pointer, Slice, or UnsafePointer.
  2037  //
  2038  // If v's Kind is Func, the returned pointer is an underlying
  2039  // code pointer, but not necessarily enough to identify a
  2040  // single function uniquely. The only guarantee is that the
  2041  // result is zero if and only if v is a nil func Value.
  2042  //
  2043  // If v's Kind is Slice, the returned pointer is to the first
  2044  // element of the slice. If the slice is nil the returned value
  2045  // is 0.  If the slice is empty but non-nil the return value is non-zero.
  2046  //
  2047  // It's preferred to use uintptr(Value.UnsafePointer()) to get the equivalent result.
  2048  func (v Value) Pointer() uintptr {
  2049  	k := v.kind()
  2050  	switch k {
  2051  	case Pointer:
  2052  		if v.typ.ptrdata == 0 {
  2053  			val := *(*uintptr)(v.ptr)
  2054  			// Since it is a not-in-heap pointer, all pointers to the heap are
  2055  			// forbidden! See comment in Value.Elem and issue #48399.
  2056  			if !verifyNotInHeapPtr(val) {
  2057  				panic("reflect: reflect.Value.Pointer on an invalid notinheap pointer")
  2058  			}
  2059  			return val
  2060  		}
  2061  		fallthrough
  2062  	case Chan, Map, UnsafePointer:
  2063  		return uintptr(v.pointer())
  2064  	case Func:
  2065  		if v.flag&flagMethod != 0 {
  2066  			// As the doc comment says, the returned pointer is an
  2067  			// underlying code pointer but not necessarily enough to
  2068  			// identify a single function uniquely. All method expressions
  2069  			// created via reflect have the same underlying code pointer,
  2070  			// so their Pointers are equal. The function used here must
  2071  			// match the one used in makeMethodValue.
  2072  			return methodValueCallCodePtr()
  2073  		}
  2074  		p := v.pointer()
  2075  		// Non-nil func value points at data block.
  2076  		// First word of data block is actual code.
  2077  		if p != nil {
  2078  			p = *(*unsafe.Pointer)(p)
  2079  		}
  2080  		return uintptr(p)
  2081  
  2082  	case Slice:
  2083  		return (*SliceHeader)(v.ptr).Data
  2084  	}
  2085  	panic(&ValueError{"reflect.Value.Pointer", v.kind()})
  2086  }
  2087  
  2088  // Recv receives and returns a value from the channel v.
  2089  // It panics if v's Kind is not Chan.
  2090  // The receive blocks until a value is ready.
  2091  // The boolean value ok is true if the value x corresponds to a send
  2092  // on the channel, false if it is a zero value received because the channel is closed.
  2093  func (v Value) Recv() (x Value, ok bool) {
  2094  	v.mustBe(Chan)
  2095  	v.mustBeExported()
  2096  	return v.recv(false)
  2097  }
  2098  
  2099  // internal recv, possibly non-blocking (nb).
  2100  // v is known to be a channel.
  2101  func (v Value) recv(nb bool) (val Value, ok bool) {
  2102  	tt := (*chanType)(unsafe.Pointer(v.typ))
  2103  	if ChanDir(tt.dir)&RecvDir == 0 {
  2104  		panic("reflect: recv on send-only channel")
  2105  	}
  2106  	t := tt.elem
  2107  	val = Value{t, nil, flag(t.Kind())}
  2108  	var p unsafe.Pointer
  2109  	if ifaceIndir(t) {
  2110  		p = unsafe_New(t)
  2111  		val.ptr = p
  2112  		val.flag |= flagIndir
  2113  	} else {
  2114  		p = unsafe.Pointer(&val.ptr)
  2115  	}
  2116  	selected, ok := chanrecv(v.pointer(), nb, p)
  2117  	if !selected {
  2118  		val = Value{}
  2119  	}
  2120  	return
  2121  }
  2122  
  2123  // Send sends x on the channel v.
  2124  // It panics if v's kind is not Chan or if x's type is not the same type as v's element type.
  2125  // As in Go, x's value must be assignable to the channel's element type.
  2126  func (v Value) Send(x Value) {
  2127  	v.mustBe(Chan)
  2128  	v.mustBeExported()
  2129  	v.send(x, false)
  2130  }
  2131  
  2132  // internal send, possibly non-blocking.
  2133  // v is known to be a channel.
  2134  func (v Value) send(x Value, nb bool) (selected bool) {
  2135  	tt := (*chanType)(unsafe.Pointer(v.typ))
  2136  	if ChanDir(tt.dir)&SendDir == 0 {
  2137  		panic("reflect: send on recv-only channel")
  2138  	}
  2139  	x.mustBeExported()
  2140  	x = x.assignTo("reflect.Value.Send", tt.elem, nil)
  2141  	var p unsafe.Pointer
  2142  	if x.flag&flagIndir != 0 {
  2143  		p = x.ptr
  2144  	} else {
  2145  		p = unsafe.Pointer(&x.ptr)
  2146  	}
  2147  	return chansend(v.pointer(), p, nb)
  2148  }
  2149  
  2150  // Set assigns x to the value v.
  2151  // It panics if CanSet returns false.
  2152  // As in Go, x's value must be assignable to v's type.
  2153  func (v Value) Set(x Value) {
  2154  	v.mustBeAssignable()
  2155  	x.mustBeExported() // do not let unexported x leak
  2156  	var target unsafe.Pointer
  2157  	if v.kind() == Interface {
  2158  		target = v.ptr
  2159  	}
  2160  	x = x.assignTo("reflect.Set", v.typ, target)
  2161  	if x.flag&flagIndir != 0 {
  2162  		if x.ptr == unsafe.Pointer(&zeroVal[0]) {
  2163  			typedmemclr(v.typ, v.ptr)
  2164  		} else {
  2165  			typedmemmove(v.typ, v.ptr, x.ptr)
  2166  		}
  2167  	} else {
  2168  		*(*unsafe.Pointer)(v.ptr) = x.ptr
  2169  	}
  2170  }
  2171  
  2172  // SetBool sets v's underlying value.
  2173  // It panics if v's Kind is not Bool or if CanSet() is false.
  2174  func (v Value) SetBool(x bool) {
  2175  	v.mustBeAssignable()
  2176  	v.mustBe(Bool)
  2177  	*(*bool)(v.ptr) = x
  2178  }
  2179  
  2180  // SetBytes sets v's underlying value.
  2181  // It panics if v's underlying value is not a slice of bytes.
  2182  func (v Value) SetBytes(x []byte) {
  2183  	v.mustBeAssignable()
  2184  	v.mustBe(Slice)
  2185  	if v.typ.Elem().Kind() != Uint8 {
  2186  		panic("reflect.Value.SetBytes of non-byte slice")
  2187  	}
  2188  	*(*[]byte)(v.ptr) = x
  2189  }
  2190  
  2191  // setRunes sets v's underlying value.
  2192  // It panics if v's underlying value is not a slice of runes (int32s).
  2193  func (v Value) setRunes(x []rune) {
  2194  	v.mustBeAssignable()
  2195  	v.mustBe(Slice)
  2196  	if v.typ.Elem().Kind() != Int32 {
  2197  		panic("reflect.Value.setRunes of non-rune slice")
  2198  	}
  2199  	*(*[]rune)(v.ptr) = x
  2200  }
  2201  
  2202  // SetComplex sets v's underlying value to x.
  2203  // It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false.
  2204  func (v Value) SetComplex(x complex128) {
  2205  	v.mustBeAssignable()
  2206  	switch k := v.kind(); k {
  2207  	default:
  2208  		panic(&ValueError{"reflect.Value.SetComplex", v.kind()})
  2209  	case Complex64:
  2210  		*(*complex64)(v.ptr) = complex64(x)
  2211  	case Complex128:
  2212  		*(*complex128)(v.ptr) = x
  2213  	}
  2214  }
  2215  
  2216  // SetFloat sets v's underlying value to x.
  2217  // It panics if v's Kind is not Float32 or Float64, or if CanSet() is false.
  2218  func (v Value) SetFloat(x float64) {
  2219  	v.mustBeAssignable()
  2220  	switch k := v.kind(); k {
  2221  	default:
  2222  		panic(&ValueError{"reflect.Value.SetFloat", v.kind()})
  2223  	case Float32:
  2224  		*(*float32)(v.ptr) = float32(x)
  2225  	case Float64:
  2226  		*(*float64)(v.ptr) = x
  2227  	}
  2228  }
  2229  
  2230  // SetInt sets v's underlying value to x.
  2231  // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false.
  2232  func (v Value) SetInt(x int64) {
  2233  	v.mustBeAssignable()
  2234  	switch k := v.kind(); k {
  2235  	default:
  2236  		panic(&ValueError{"reflect.Value.SetInt", v.kind()})
  2237  	case Int:
  2238  		*(*int)(v.ptr) = int(x)
  2239  	case Int8:
  2240  		*(*int8)(v.ptr) = int8(x)
  2241  	case Int16:
  2242  		*(*int16)(v.ptr) = int16(x)
  2243  	case Int32:
  2244  		*(*int32)(v.ptr) = int32(x)
  2245  	case Int64:
  2246  		*(*int64)(v.ptr) = x
  2247  	}
  2248  }
  2249  
  2250  // SetLen sets v's length to n.
  2251  // It panics if v's Kind is not Slice or if n is negative or
  2252  // greater than the capacity of the slice.
  2253  func (v Value) SetLen(n int) {
  2254  	v.mustBeAssignable()
  2255  	v.mustBe(Slice)
  2256  	s := (*unsafeheader.Slice)(v.ptr)
  2257  	if uint(n) > uint(s.Cap) {
  2258  		panic("reflect: slice length out of range in SetLen")
  2259  	}
  2260  	s.Len = n
  2261  }
  2262  
  2263  // SetCap sets v's capacity to n.
  2264  // It panics if v's Kind is not Slice or if n is smaller than the length or
  2265  // greater than the capacity of the slice.
  2266  func (v Value) SetCap(n int) {
  2267  	v.mustBeAssignable()
  2268  	v.mustBe(Slice)
  2269  	s := (*unsafeheader.Slice)(v.ptr)
  2270  	if n < s.Len || n > s.Cap {
  2271  		panic("reflect: slice capacity out of range in SetCap")
  2272  	}
  2273  	s.Cap = n
  2274  }
  2275  
  2276  // SetMapIndex sets the element associated with key in the map v to elem.
  2277  // It panics if v's Kind is not Map.
  2278  // If elem is the zero Value, SetMapIndex deletes the key from the map.
  2279  // Otherwise if v holds a nil map, SetMapIndex will panic.
  2280  // As in Go, key's elem must be assignable to the map's key type,
  2281  // and elem's value must be assignable to the map's elem type.
  2282  func (v Value) SetMapIndex(key, elem Value) {
  2283  	v.mustBe(Map)
  2284  	v.mustBeExported()
  2285  	key.mustBeExported()
  2286  	tt := (*mapType)(unsafe.Pointer(v.typ))
  2287  
  2288  	if (tt.key == stringType || key.kind() == String) && tt.key == key.typ && tt.elem.size <= maxValSize {
  2289  		k := *(*string)(key.ptr)
  2290  		if elem.typ == nil {
  2291  			mapdelete_faststr(v.typ, v.pointer(), k)
  2292  			return
  2293  		}
  2294  		elem.mustBeExported()
  2295  		elem = elem.assignTo("reflect.Value.SetMapIndex", tt.elem, nil)
  2296  		var e unsafe.Pointer
  2297  		if elem.flag&flagIndir != 0 {
  2298  			e = elem.ptr
  2299  		} else {
  2300  			e = unsafe.Pointer(&elem.ptr)
  2301  		}
  2302  		mapassign_faststr(v.typ, v.pointer(), k, e)
  2303  		return
  2304  	}
  2305  
  2306  	key = key.assignTo("reflect.Value.SetMapIndex", tt.key, nil)
  2307  	var k unsafe.Pointer
  2308  	if key.flag&flagIndir != 0 {
  2309  		k = key.ptr
  2310  	} else {
  2311  		k = unsafe.Pointer(&key.ptr)
  2312  	}
  2313  	if elem.typ == nil {
  2314  		mapdelete(v.typ, v.pointer(), k)
  2315  		return
  2316  	}
  2317  	elem.mustBeExported()
  2318  	elem = elem.assignTo("reflect.Value.SetMapIndex", tt.elem, nil)
  2319  	var e unsafe.Pointer
  2320  	if elem.flag&flagIndir != 0 {
  2321  		e = elem.ptr
  2322  	} else {
  2323  		e = unsafe.Pointer(&elem.ptr)
  2324  	}
  2325  	mapassign(v.typ, v.pointer(), k, e)
  2326  }
  2327  
  2328  // SetUint sets v's underlying value to x.
  2329  // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false.
  2330  func (v Value) SetUint(x uint64) {
  2331  	v.mustBeAssignable()
  2332  	switch k := v.kind(); k {
  2333  	default:
  2334  		panic(&ValueError{"reflect.Value.SetUint", v.kind()})
  2335  	case Uint:
  2336  		*(*uint)(v.ptr) = uint(x)
  2337  	case Uint8:
  2338  		*(*uint8)(v.ptr) = uint8(x)
  2339  	case Uint16:
  2340  		*(*uint16)(v.ptr) = uint16(x)
  2341  	case Uint32:
  2342  		*(*uint32)(v.ptr) = uint32(x)
  2343  	case Uint64:
  2344  		*(*uint64)(v.ptr) = x
  2345  	case Uintptr:
  2346  		*(*uintptr)(v.ptr) = uintptr(x)
  2347  	}
  2348  }
  2349  
  2350  // SetPointer sets the unsafe.Pointer value v to x.
  2351  // It panics if v's Kind is not UnsafePointer.
  2352  func (v Value) SetPointer(x unsafe.Pointer) {
  2353  	v.mustBeAssignable()
  2354  	v.mustBe(UnsafePointer)
  2355  	*(*unsafe.Pointer)(v.ptr) = x
  2356  }
  2357  
  2358  // SetString sets v's underlying value to x.
  2359  // It panics if v's Kind is not String or if CanSet() is false.
  2360  func (v Value) SetString(x string) {
  2361  	v.mustBeAssignable()
  2362  	v.mustBe(String)
  2363  	*(*string)(v.ptr) = x
  2364  }
  2365  
  2366  // Slice returns v[i:j].
  2367  // It panics if v's Kind is not Array, Slice or String, or if v is an unaddressable array,
  2368  // or if the indexes are out of bounds.
  2369  func (v Value) Slice(i, j int) Value {
  2370  	var (
  2371  		cap  int
  2372  		typ  *sliceType
  2373  		base unsafe.Pointer
  2374  	)
  2375  	switch kind := v.kind(); kind {
  2376  	default:
  2377  		panic(&ValueError{"reflect.Value.Slice", v.kind()})
  2378  
  2379  	case Array:
  2380  		if v.flag&flagAddr == 0 {
  2381  			panic("reflect.Value.Slice: slice of unaddressable array")
  2382  		}
  2383  		tt := (*arrayType)(unsafe.Pointer(v.typ))
  2384  		cap = int(tt.len)
  2385  		typ = (*sliceType)(unsafe.Pointer(tt.slice))
  2386  		base = v.ptr
  2387  
  2388  	case Slice:
  2389  		typ = (*sliceType)(unsafe.Pointer(v.typ))
  2390  		s := (*unsafeheader.Slice)(v.ptr)
  2391  		base = s.Data
  2392  		cap = s.Cap
  2393  
  2394  	case String:
  2395  		s := (*unsafeheader.String)(v.ptr)
  2396  		if i < 0 || j < i || j > s.Len {
  2397  			panic("reflect.Value.Slice: string slice index out of bounds")
  2398  		}
  2399  		var t unsafeheader.String
  2400  		if i < s.Len {
  2401  			t = unsafeheader.String{Data: arrayAt(s.Data, i, 1, "i < s.Len"), Len: j - i}
  2402  		}
  2403  		return Value{v.typ, unsafe.Pointer(&t), v.flag}
  2404  	}
  2405  
  2406  	if i < 0 || j < i || j > cap {
  2407  		panic("reflect.Value.Slice: slice index out of bounds")
  2408  	}
  2409  
  2410  	// Declare slice so that gc can see the base pointer in it.
  2411  	var x []unsafe.Pointer
  2412  
  2413  	// Reinterpret as *unsafeheader.Slice to edit.
  2414  	s := (*unsafeheader.Slice)(unsafe.Pointer(&x))
  2415  	s.Len = j - i
  2416  	s.Cap = cap - i
  2417  	if cap-i > 0 {
  2418  		s.Data = arrayAt(base, i, typ.elem.Size(), "i < cap")
  2419  	} else {
  2420  		// do not advance pointer, to avoid pointing beyond end of slice
  2421  		s.Data = base
  2422  	}
  2423  
  2424  	fl := v.flag.ro() | flagIndir | flag(Slice)
  2425  	return Value{typ.common(), unsafe.Pointer(&x), fl}
  2426  }
  2427  
  2428  // Slice3 is the 3-index form of the slice operation: it returns v[i:j:k].
  2429  // It panics if v's Kind is not Array or Slice, or if v is an unaddressable array,
  2430  // or if the indexes are out of bounds.
  2431  func (v Value) Slice3(i, j, k int) Value {
  2432  	var (
  2433  		cap  int
  2434  		typ  *sliceType
  2435  		base unsafe.Pointer
  2436  	)
  2437  	switch kind := v.kind(); kind {
  2438  	default:
  2439  		panic(&ValueError{"reflect.Value.Slice3", v.kind()})
  2440  
  2441  	case Array:
  2442  		if v.flag&flagAddr == 0 {
  2443  			panic("reflect.Value.Slice3: slice of unaddressable array")
  2444  		}
  2445  		tt := (*arrayType)(unsafe.Pointer(v.typ))
  2446  		cap = int(tt.len)
  2447  		typ = (*sliceType)(unsafe.Pointer(tt.slice))
  2448  		base = v.ptr
  2449  
  2450  	case Slice:
  2451  		typ = (*sliceType)(unsafe.Pointer(v.typ))
  2452  		s := (*unsafeheader.Slice)(v.ptr)
  2453  		base = s.Data
  2454  		cap = s.Cap
  2455  	}
  2456  
  2457  	if i < 0 || j < i || k < j || k > cap {
  2458  		panic("reflect.Value.Slice3: slice index out of bounds")
  2459  	}
  2460  
  2461  	// Declare slice so that the garbage collector
  2462  	// can see the base pointer in it.
  2463  	var x []unsafe.Pointer
  2464  
  2465  	// Reinterpret as *unsafeheader.Slice to edit.
  2466  	s := (*unsafeheader.Slice)(unsafe.Pointer(&x))
  2467  	s.Len = j - i
  2468  	s.Cap = k - i
  2469  	if k-i > 0 {
  2470  		s.Data = arrayAt(base, i, typ.elem.Size(), "i < k <= cap")
  2471  	} else {
  2472  		// do not advance pointer, to avoid pointing beyond end of slice
  2473  		s.Data = base
  2474  	}
  2475  
  2476  	fl := v.flag.ro() | flagIndir | flag(Slice)
  2477  	return Value{typ.common(), unsafe.Pointer(&x), fl}
  2478  }
  2479  
  2480  // String returns the string v's underlying value, as a string.
  2481  // String is a special case because of Go's String method convention.
  2482  // Unlike the other getters, it does not panic if v's Kind is not String.
  2483  // Instead, it returns a string of the form "<T value>" where T is v's type.
  2484  // The fmt package treats Values specially. It does not call their String
  2485  // method implicitly but instead prints the concrete values they hold.
  2486  func (v Value) String() string {
  2487  	// stringNonString is split out to keep String inlineable for string kinds.
  2488  	if v.kind() == String {
  2489  		return *(*string)(v.ptr)
  2490  	}
  2491  	return v.stringNonString()
  2492  }
  2493  
  2494  func (v Value) stringNonString() string {
  2495  	if v.kind() == Invalid {
  2496  		return "<invalid Value>"
  2497  	}
  2498  	// If you call String on a reflect.Value of other type, it's better to
  2499  	// print something than to panic. Useful in debugging.
  2500  	return "<" + v.Type().String() + " Value>"
  2501  }
  2502  
  2503  // TryRecv attempts to receive a value from the channel v but will not block.
  2504  // It panics if v's Kind is not Chan.
  2505  // If the receive delivers a value, x is the transferred value and ok is true.
  2506  // If the receive cannot finish without blocking, x is the zero Value and ok is false.
  2507  // If the channel is closed, x is the zero value for the channel's element type and ok is false.
  2508  func (v Value) TryRecv() (x Value, ok bool) {
  2509  	v.mustBe(Chan)
  2510  	v.mustBeExported()
  2511  	return v.recv(true)
  2512  }
  2513  
  2514  // TrySend attempts to send x on the channel v but will not block.
  2515  // It panics if v's Kind is not Chan.
  2516  // It reports whether the value was sent.
  2517  // As in Go, x's value must be assignable to the channel's element type.
  2518  func (v Value) TrySend(x Value) bool {
  2519  	v.mustBe(Chan)
  2520  	v.mustBeExported()
  2521  	return v.send(x, true)
  2522  }
  2523  
  2524  // Type returns v's type.
  2525  func (v Value) Type() Type {
  2526  	if v.flag != 0 && v.flag&flagMethod == 0 {
  2527  		return v.typ
  2528  	}
  2529  	return v.typeSlow()
  2530  }
  2531  
  2532  func (v Value) typeSlow() Type {
  2533  	if v.flag == 0 {
  2534  		panic(&ValueError{"reflect.Value.Type", Invalid})
  2535  	}
  2536  	if v.flag&flagMethod == 0 {
  2537  		return v.typ
  2538  	}
  2539  
  2540  	// Method value.
  2541  	// v.typ describes the receiver, not the method type.
  2542  	i := int(v.flag) >> flagMethodShift
  2543  	if v.typ.Kind() == Interface {
  2544  		// Method on interface.
  2545  		tt := (*interfaceType)(unsafe.Pointer(v.typ))
  2546  		if uint(i) >= uint(len(tt.methods)) {
  2547  			panic("reflect: internal error: invalid method index")
  2548  		}
  2549  		m := &tt.methods[i]
  2550  		return v.typ.typeOff(m.typ)
  2551  	}
  2552  	// Method on concrete type.
  2553  	ms := v.typ.exportedMethods()
  2554  	if uint(i) >= uint(len(ms)) {
  2555  		panic("reflect: internal error: invalid method index")
  2556  	}
  2557  	m := ms[i]
  2558  	return v.typ.typeOff(m.mtyp)
  2559  }
  2560  
  2561  // CanUint reports whether Uint can be used without panicking.
  2562  func (v Value) CanUint() bool {
  2563  	switch v.kind() {
  2564  	case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  2565  		return true
  2566  	default:
  2567  		return false
  2568  	}
  2569  }
  2570  
  2571  // Uint returns v's underlying value, as a uint64.
  2572  // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
  2573  func (v Value) Uint() uint64 {
  2574  	k := v.kind()
  2575  	p := v.ptr
  2576  	switch k {
  2577  	case Uint:
  2578  		return uint64(*(*uint)(p))
  2579  	case Uint8:
  2580  		return uint64(*(*uint8)(p))
  2581  	case Uint16:
  2582  		return uint64(*(*uint16)(p))
  2583  	case Uint32:
  2584  		return uint64(*(*uint32)(p))
  2585  	case Uint64:
  2586  		return *(*uint64)(p)
  2587  	case Uintptr:
  2588  		return uint64(*(*uintptr)(p))
  2589  	}
  2590  	panic(&ValueError{"reflect.Value.Uint", v.kind()})
  2591  }
  2592  
  2593  //go:nocheckptr
  2594  // This prevents inlining Value.UnsafeAddr when -d=checkptr is enabled,
  2595  // which ensures cmd/compile can recognize unsafe.Pointer(v.UnsafeAddr())
  2596  // and make an exception.
  2597  
  2598  // UnsafeAddr returns a pointer to v's data, as a uintptr.
  2599  // It is for advanced clients that also import the "unsafe" package.
  2600  // It panics if v is not addressable.
  2601  //
  2602  // It's preferred to use uintptr(Value.Addr().UnsafePointer()) to get the equivalent result.
  2603  func (v Value) UnsafeAddr() uintptr {
  2604  	if v.typ == nil {
  2605  		panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid})
  2606  	}
  2607  	if v.flag&flagAddr == 0 {
  2608  		panic("reflect.Value.UnsafeAddr of unaddressable value")
  2609  	}
  2610  	return uintptr(v.ptr)
  2611  }
  2612  
  2613  // UnsafePointer returns v's value as a unsafe.Pointer.
  2614  // It panics if v's Kind is not Chan, Func, Map, Pointer, Slice, or UnsafePointer.
  2615  //
  2616  // If v's Kind is Func, the returned pointer is an underlying
  2617  // code pointer, but not necessarily enough to identify a
  2618  // single function uniquely. The only guarantee is that the
  2619  // result is zero if and only if v is a nil func Value.
  2620  //
  2621  // If v's Kind is Slice, the returned pointer is to the first
  2622  // element of the slice. If the slice is nil the returned value
  2623  // is nil.  If the slice is empty but non-nil the return value is non-nil.
  2624  func (v Value) UnsafePointer() unsafe.Pointer {
  2625  	k := v.kind()
  2626  	switch k {
  2627  	case Pointer:
  2628  		if v.typ.ptrdata == 0 {
  2629  			// Since it is a not-in-heap pointer, all pointers to the heap are
  2630  			// forbidden! See comment in Value.Elem and issue #48399.
  2631  			if !verifyNotInHeapPtr(*(*uintptr)(v.ptr)) {
  2632  				panic("reflect: reflect.Value.UnsafePointer on an invalid notinheap pointer")
  2633  			}
  2634  			return *(*unsafe.Pointer)(v.ptr)
  2635  		}
  2636  		fallthrough
  2637  	case Chan, Map, UnsafePointer:
  2638  		return v.pointer()
  2639  	case Func:
  2640  		if v.flag&flagMethod != 0 {
  2641  			// As the doc comment says, the returned pointer is an
  2642  			// underlying code pointer but not necessarily enough to
  2643  			// identify a single function uniquely. All method expressions
  2644  			// created via reflect have the same underlying code pointer,
  2645  			// so their Pointers are equal. The function used here must
  2646  			// match the one used in makeMethodValue.
  2647  			code := methodValueCallCodePtr()
  2648  			return *(*unsafe.Pointer)(unsafe.Pointer(&code))
  2649  		}
  2650  		p := v.pointer()
  2651  		// Non-nil func value points at data block.
  2652  		// First word of data block is actual code.
  2653  		if p != nil {
  2654  			p = *(*unsafe.Pointer)(p)
  2655  		}
  2656  		return p
  2657  
  2658  	case Slice:
  2659  		return (*unsafeheader.Slice)(v.ptr).Data
  2660  	}
  2661  	panic(&ValueError{"reflect.Value.UnsafePointer", v.kind()})
  2662  }
  2663  
  2664  // StringHeader is the runtime representation of a string.
  2665  // It cannot be used safely or portably and its representation may
  2666  // change in a later release.
  2667  // Moreover, the Data field is not sufficient to guarantee the data
  2668  // it references will not be garbage collected, so programs must keep
  2669  // a separate, correctly typed pointer to the underlying data.
  2670  type StringHeader struct {
  2671  	Data uintptr
  2672  	Len  int
  2673  }
  2674  
  2675  // SliceHeader is the runtime representation of a slice.
  2676  // It cannot be used safely or portably and its representation may
  2677  // change in a later release.
  2678  // Moreover, the Data field is not sufficient to guarantee the data
  2679  // it references will not be garbage collected, so programs must keep
  2680  // a separate, correctly typed pointer to the underlying data.
  2681  type SliceHeader struct {
  2682  	Data uintptr
  2683  	Len  int
  2684  	Cap  int
  2685  }
  2686  
  2687  func typesMustMatch(what string, t1, t2 Type) {
  2688  	if t1 != t2 {
  2689  		panic(what + ": " + t1.String() + " != " + t2.String())
  2690  	}
  2691  }
  2692  
  2693  // arrayAt returns the i-th element of p,
  2694  // an array whose elements are eltSize bytes wide.
  2695  // The array pointed at by p must have at least i+1 elements:
  2696  // it is invalid (but impossible to check here) to pass i >= len,
  2697  // because then the result will point outside the array.
  2698  // whySafe must explain why i < len. (Passing "i < len" is fine;
  2699  // the benefit is to surface this assumption at the call site.)
  2700  func arrayAt(p unsafe.Pointer, i int, eltSize uintptr, whySafe string) unsafe.Pointer {
  2701  	return add(p, uintptr(i)*eltSize, "i < len")
  2702  }
  2703  
  2704  // grow grows the slice s so that it can hold extra more values, allocating
  2705  // more capacity if needed. It also returns the old and new slice lengths.
  2706  func grow(s Value, extra int) (Value, int, int) {
  2707  	i0 := s.Len()
  2708  	i1 := i0 + extra
  2709  	if i1 < i0 {
  2710  		panic("reflect.Append: slice overflow")
  2711  	}
  2712  	m := s.Cap()
  2713  	if i1 <= m {
  2714  		return s.Slice(0, i1), i0, i1
  2715  	}
  2716  	if m == 0 {
  2717  		m = extra
  2718  	} else {
  2719  		const threshold = 256
  2720  		for m < i1 {
  2721  			if i0 < threshold {
  2722  				m += m
  2723  			} else {
  2724  				m += (m + 3*threshold) / 4
  2725  			}
  2726  		}
  2727  	}
  2728  	t := MakeSlice(s.Type(), i1, m)
  2729  	Copy(t, s)
  2730  	return t, i0, i1
  2731  }
  2732  
  2733  // Append appends the values x to a slice s and returns the resulting slice.
  2734  // As in Go, each x's value must be assignable to the slice's element type.
  2735  func Append(s Value, x ...Value) Value {
  2736  	s.mustBe(Slice)
  2737  	s, i0, i1 := grow(s, len(x))
  2738  	for i, j := i0, 0; i < i1; i, j = i+1, j+1 {
  2739  		s.Index(i).Set(x[j])
  2740  	}
  2741  	return s
  2742  }
  2743  
  2744  // AppendSlice appends a slice t to a slice s and returns the resulting slice.
  2745  // The slices s and t must have the same element type.
  2746  func AppendSlice(s, t Value) Value {
  2747  	s.mustBe(Slice)
  2748  	t.mustBe(Slice)
  2749  	typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem())
  2750  	s, i0, i1 := grow(s, t.Len())
  2751  	Copy(s.Slice(i0, i1), t)
  2752  	return s
  2753  }
  2754  
  2755  // Copy copies the contents of src into dst until either
  2756  // dst has been filled or src has been exhausted.
  2757  // It returns the number of elements copied.
  2758  // Dst and src each must have kind Slice or Array, and
  2759  // dst and src must have the same element type.
  2760  //
  2761  // As a special case, src can have kind String if the element type of dst is kind Uint8.
  2762  func Copy(dst, src Value) int {
  2763  	dk := dst.kind()
  2764  	if dk != Array && dk != Slice {
  2765  		panic(&ValueError{"reflect.Copy", dk})
  2766  	}
  2767  	if dk == Array {
  2768  		dst.mustBeAssignable()
  2769  	}
  2770  	dst.mustBeExported()
  2771  
  2772  	sk := src.kind()
  2773  	var stringCopy bool
  2774  	if sk != Array && sk != Slice {
  2775  		stringCopy = sk == String && dst.typ.Elem().Kind() == Uint8
  2776  		if !stringCopy {
  2777  			panic(&ValueError{"reflect.Copy", sk})
  2778  		}
  2779  	}
  2780  	src.mustBeExported()
  2781  
  2782  	de := dst.typ.Elem()
  2783  	if !stringCopy {
  2784  		se := src.typ.Elem()
  2785  		typesMustMatch("reflect.Copy", de, se)
  2786  	}
  2787  
  2788  	var ds, ss unsafeheader.Slice
  2789  	if dk == Array {
  2790  		ds.Data = dst.ptr
  2791  		ds.Len = dst.Len()
  2792  		ds.Cap = ds.Len
  2793  	} else {
  2794  		ds = *(*unsafeheader.Slice)(dst.ptr)
  2795  	}
  2796  	if sk == Array {
  2797  		ss.Data = src.ptr
  2798  		ss.Len = src.Len()
  2799  		ss.Cap = ss.Len
  2800  	} else if sk == Slice {
  2801  		ss = *(*unsafeheader.Slice)(src.ptr)
  2802  	} else {
  2803  		sh := *(*unsafeheader.String)(src.ptr)
  2804  		ss.Data = sh.Data
  2805  		ss.Len = sh.Len
  2806  		ss.Cap = sh.Len
  2807  	}
  2808  
  2809  	return typedslicecopy(de.common(), ds, ss)
  2810  }
  2811  
  2812  // A runtimeSelect is a single case passed to rselect.
  2813  // This must match ../runtime/select.go:/runtimeSelect
  2814  type runtimeSelect struct {
  2815  	dir SelectDir      // SelectSend, SelectRecv or SelectDefault
  2816  	typ *rtype         // channel type
  2817  	ch  unsafe.Pointer // channel
  2818  	val unsafe.Pointer // ptr to data (SendDir) or ptr to receive buffer (RecvDir)
  2819  }
  2820  
  2821  // rselect runs a select. It returns the index of the chosen case.
  2822  // If the case was a receive, val is filled in with the received value.
  2823  // The conventional OK bool indicates whether the receive corresponds
  2824  // to a sent value.
  2825  //
  2826  //go:noescape
  2827  func rselect([]runtimeSelect) (chosen int, recvOK bool)
  2828  
  2829  // A SelectDir describes the communication direction of a select case.
  2830  type SelectDir int
  2831  
  2832  // NOTE: These values must match ../runtime/select.go:/selectDir.
  2833  
  2834  const (
  2835  	_             SelectDir = iota
  2836  	SelectSend              // case Chan <- Send
  2837  	SelectRecv              // case <-Chan:
  2838  	SelectDefault           // default
  2839  )
  2840  
  2841  // A SelectCase describes a single case in a select operation.
  2842  // The kind of case depends on Dir, the communication direction.
  2843  //
  2844  // If Dir is SelectDefault, the case represents a default case.
  2845  // Chan and Send must be zero Values.
  2846  //
  2847  // If Dir is SelectSend, the case represents a send operation.
  2848  // Normally Chan's underlying value must be a channel, and Send's underlying value must be
  2849  // assignable to the channel's element type. As a special case, if Chan is a zero Value,
  2850  // then the case is ignored, and the field Send will also be ignored and may be either zero
  2851  // or non-zero.
  2852  //
  2853  // If Dir is SelectRecv, the case represents a receive operation.
  2854  // Normally Chan's underlying value must be a channel and Send must be a zero Value.
  2855  // If Chan is a zero Value, then the case is ignored, but Send must still be a zero Value.
  2856  // When a receive operation is selected, the received Value is returned by Select.
  2857  type SelectCase struct {
  2858  	Dir  SelectDir // direction of case
  2859  	Chan Value     // channel to use (for send or receive)
  2860  	Send Value     // value to send (for send)
  2861  }
  2862  
  2863  // Select executes a select operation described by the list of cases.
  2864  // Like the Go select statement, it blocks until at least one of the cases
  2865  // can proceed, makes a uniform pseudo-random choice,
  2866  // and then executes that case. It returns the index of the chosen case
  2867  // and, if that case was a receive operation, the value received and a
  2868  // boolean indicating whether the value corresponds to a send on the channel
  2869  // (as opposed to a zero value received because the channel is closed).
  2870  // Select supports a maximum of 65536 cases.
  2871  func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool) {
  2872  	if len(cases) > 65536 {
  2873  		panic("reflect.Select: too many cases (max 65536)")
  2874  	}
  2875  	// NOTE: Do not trust that caller is not modifying cases data underfoot.
  2876  	// The range is safe because the caller cannot modify our copy of the len
  2877  	// and each iteration makes its own copy of the value c.
  2878  	var runcases []runtimeSelect
  2879  	if len(cases) > 4 {
  2880  		// Slice is heap allocated due to runtime dependent capacity.
  2881  		runcases = make([]runtimeSelect, len(cases))
  2882  	} else {
  2883  		// Slice can be stack allocated due to constant capacity.
  2884  		runcases = make([]runtimeSelect, len(cases), 4)
  2885  	}
  2886  
  2887  	haveDefault := false
  2888  	for i, c := range cases {
  2889  		rc := &runcases[i]
  2890  		rc.dir = c.Dir
  2891  		switch c.Dir {
  2892  		default:
  2893  			panic("reflect.Select: invalid Dir")
  2894  
  2895  		case SelectDefault: // default
  2896  			if haveDefault {
  2897  				panic("reflect.Select: multiple default cases")
  2898  			}
  2899  			haveDefault = true
  2900  			if c.Chan.IsValid() {
  2901  				panic("reflect.Select: default case has Chan value")
  2902  			}
  2903  			if c.Send.IsValid() {
  2904  				panic("reflect.Select: default case has Send value")
  2905  			}
  2906  
  2907  		case SelectSend:
  2908  			ch := c.Chan
  2909  			if !ch.IsValid() {
  2910  				break
  2911  			}
  2912  			ch.mustBe(Chan)
  2913  			ch.mustBeExported()
  2914  			tt := (*chanType)(unsafe.Pointer(ch.typ))
  2915  			if ChanDir(tt.dir)&SendDir == 0 {
  2916  				panic("reflect.Select: SendDir case using recv-only channel")
  2917  			}
  2918  			rc.ch = ch.pointer()
  2919  			rc.typ = &tt.rtype
  2920  			v := c.Send
  2921  			if !v.IsValid() {
  2922  				panic("reflect.Select: SendDir case missing Send value")
  2923  			}
  2924  			v.mustBeExported()
  2925  			v = v.assignTo("reflect.Select", tt.elem, nil)
  2926  			if v.flag&flagIndir != 0 {
  2927  				rc.val = v.ptr
  2928  			} else {
  2929  				rc.val = unsafe.Pointer(&v.ptr)
  2930  			}
  2931  
  2932  		case SelectRecv:
  2933  			if c.Send.IsValid() {
  2934  				panic("reflect.Select: RecvDir case has Send value")
  2935  			}
  2936  			ch := c.Chan
  2937  			if !ch.IsValid() {
  2938  				break
  2939  			}
  2940  			ch.mustBe(Chan)
  2941  			ch.mustBeExported()
  2942  			tt := (*chanType)(unsafe.Pointer(ch.typ))
  2943  			if ChanDir(tt.dir)&RecvDir == 0 {
  2944  				panic("reflect.Select: RecvDir case using send-only channel")
  2945  			}
  2946  			rc.ch = ch.pointer()
  2947  			rc.typ = &tt.rtype
  2948  			rc.val = unsafe_New(tt.elem)
  2949  		}
  2950  	}
  2951  
  2952  	chosen, recvOK = rselect(runcases)
  2953  	if runcases[chosen].dir == SelectRecv {
  2954  		tt := (*chanType)(unsafe.Pointer(runcases[chosen].typ))
  2955  		t := tt.elem
  2956  		p := runcases[chosen].val
  2957  		fl := flag(t.Kind())
  2958  		if ifaceIndir(t) {
  2959  			recv = Value{t, p, fl | flagIndir}
  2960  		} else {
  2961  			recv = Value{t, *(*unsafe.Pointer)(p), fl}
  2962  		}
  2963  	}
  2964  	return chosen, recv, recvOK
  2965  }
  2966  
  2967  /*
  2968   * constructors
  2969   */
  2970  
  2971  // implemented in package runtime
  2972  func unsafe_New(*rtype) unsafe.Pointer
  2973  func unsafe_NewArray(*rtype, int) unsafe.Pointer
  2974  
  2975  // MakeSlice creates a new zero-initialized slice value
  2976  // for the specified slice type, length, and capacity.
  2977  func MakeSlice(typ Type, len, cap int) Value {
  2978  	if typ.Kind() != Slice {
  2979  		panic("reflect.MakeSlice of non-slice type")
  2980  	}
  2981  	if len < 0 {
  2982  		panic("reflect.MakeSlice: negative len")
  2983  	}
  2984  	if cap < 0 {
  2985  		panic("reflect.MakeSlice: negative cap")
  2986  	}
  2987  	if len > cap {
  2988  		panic("reflect.MakeSlice: len > cap")
  2989  	}
  2990  
  2991  	s := unsafeheader.Slice{Data: unsafe_NewArray(typ.Elem().(*rtype), cap), Len: len, Cap: cap}
  2992  	return Value{typ.(*rtype), unsafe.Pointer(&s), flagIndir | flag(Slice)}
  2993  }
  2994  
  2995  // MakeChan creates a new channel with the specified type and buffer size.
  2996  func MakeChan(typ Type, buffer int) Value {
  2997  	if typ.Kind() != Chan {
  2998  		panic("reflect.MakeChan of non-chan type")
  2999  	}
  3000  	if buffer < 0 {
  3001  		panic("reflect.MakeChan: negative buffer size")
  3002  	}
  3003  	if typ.ChanDir() != BothDir {
  3004  		panic("reflect.MakeChan: unidirectional channel type")
  3005  	}
  3006  	t := typ.(*rtype)
  3007  	ch := makechan(t, buffer)
  3008  	return Value{t, ch, flag(Chan)}
  3009  }
  3010  
  3011  // MakeMap creates a new map with the specified type.
  3012  func MakeMap(typ Type) Value {
  3013  	return MakeMapWithSize(typ, 0)
  3014  }
  3015  
  3016  // MakeMapWithSize creates a new map with the specified type
  3017  // and initial space for approximately n elements.
  3018  func MakeMapWithSize(typ Type, n int) Value {
  3019  	if typ.Kind() != Map {
  3020  		panic("reflect.MakeMapWithSize of non-map type")
  3021  	}
  3022  	t := typ.(*rtype)
  3023  	m := makemap(t, n)
  3024  	return Value{t, m, flag(Map)}
  3025  }
  3026  
  3027  // Indirect returns the value that v points to.
  3028  // If v is a nil pointer, Indirect returns a zero Value.
  3029  // If v is not a pointer, Indirect returns v.
  3030  func Indirect(v Value) Value {
  3031  	if v.Kind() != Pointer {
  3032  		return v
  3033  	}
  3034  	return v.Elem()
  3035  }
  3036  
  3037  // ValueOf returns a new Value initialized to the concrete value
  3038  // stored in the interface i. ValueOf(nil) returns the zero Value.
  3039  func ValueOf(i any) Value {
  3040  	if i == nil {
  3041  		return Value{}
  3042  	}
  3043  
  3044  	// TODO: Maybe allow contents of a Value to live on the stack.
  3045  	// For now we make the contents always escape to the heap. It
  3046  	// makes life easier in a few places (see chanrecv/mapassign
  3047  	// comment below).
  3048  	escapes(i)
  3049  
  3050  	return unpackEface(i)
  3051  }
  3052  
  3053  // Zero returns a Value representing the zero value for the specified type.
  3054  // The result is different from the zero value of the Value struct,
  3055  // which represents no value at all.
  3056  // For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0.
  3057  // The returned value is neither addressable nor settable.
  3058  func Zero(typ Type) Value {
  3059  	if typ == nil {
  3060  		panic("reflect: Zero(nil)")
  3061  	}
  3062  	t := typ.(*rtype)
  3063  	fl := flag(t.Kind())
  3064  	if ifaceIndir(t) {
  3065  		var p unsafe.Pointer
  3066  		if t.size <= maxZero {
  3067  			p = unsafe.Pointer(&zeroVal[0])
  3068  		} else {
  3069  			p = unsafe_New(t)
  3070  		}
  3071  		return Value{t, p, fl | flagIndir}
  3072  	}
  3073  	return Value{t, nil, fl}
  3074  }
  3075  
  3076  // must match declarations in runtime/map.go.
  3077  const maxZero = 1024
  3078  
  3079  //go:linkname zeroVal runtime.zeroVal
  3080  var zeroVal [maxZero]byte
  3081  
  3082  // New returns a Value representing a pointer to a new zero value
  3083  // for the specified type. That is, the returned Value's Type is PointerTo(typ).
  3084  func New(typ Type) Value {
  3085  	if typ == nil {
  3086  		panic("reflect: New(nil)")
  3087  	}
  3088  	t := typ.(*rtype)
  3089  	pt := t.ptrTo()
  3090  	if ifaceIndir(pt) {
  3091  		// This is a pointer to a go:notinheap type.
  3092  		panic("reflect: New of type that may not be allocated in heap (possibly undefined cgo C type)")
  3093  	}
  3094  	ptr := unsafe_New(t)
  3095  	fl := flag(Pointer)
  3096  	return Value{pt, ptr, fl}
  3097  }
  3098  
  3099  // NewAt returns a Value representing a pointer to a value of the
  3100  // specified type, using p as that pointer.
  3101  func NewAt(typ Type, p unsafe.Pointer) Value {
  3102  	fl := flag(Pointer)
  3103  	t := typ.(*rtype)
  3104  	return Value{t.ptrTo(), p, fl}
  3105  }
  3106  
  3107  // assignTo returns a value v that can be assigned directly to dst.
  3108  // It panics if v is not assignable to dst.
  3109  // For a conversion to an interface type, target, if not nil,
  3110  // is a suggested scratch space to use.
  3111  // target must be initialized memory (or nil).
  3112  func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value {
  3113  	if v.flag&flagMethod != 0 {
  3114  		v = makeMethodValue(context, v)
  3115  	}
  3116  
  3117  	switch {
  3118  	case directlyAssignable(dst, v.typ):
  3119  		// Overwrite type so that they match.
  3120  		// Same memory layout, so no harm done.
  3121  		fl := v.flag&(flagAddr|flagIndir) | v.flag.ro()
  3122  		fl |= flag(dst.Kind())
  3123  		return Value{dst, v.ptr, fl}
  3124  
  3125  	case implements(dst, v.typ):
  3126  		if v.Kind() == Interface && v.IsNil() {
  3127  			// A nil ReadWriter passed to nil Reader is OK,
  3128  			// but using ifaceE2I below will panic.
  3129  			// Avoid the panic by returning a nil dst (e.g., Reader) explicitly.
  3130  			return Value{dst, nil, flag(Interface)}
  3131  		}
  3132  		x := valueInterface(v, false)
  3133  		if target == nil {
  3134  			target = unsafe_New(dst)
  3135  		}
  3136  		if dst.NumMethod() == 0 {
  3137  			*(*any)(target) = x
  3138  		} else {
  3139  			ifaceE2I(dst, x, target)
  3140  		}
  3141  		return Value{dst, target, flagIndir | flag(Interface)}
  3142  	}
  3143  
  3144  	// Failed.
  3145  	panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String())
  3146  }
  3147  
  3148  // Convert returns the value v converted to type t.
  3149  // If the usual Go conversion rules do not allow conversion
  3150  // of the value v to type t, or if converting v to type t panics, Convert panics.
  3151  func (v Value) Convert(t Type) Value {
  3152  	if v.flag&flagMethod != 0 {
  3153  		v = makeMethodValue("Convert", v)
  3154  	}
  3155  	op := convertOp(t.common(), v.typ)
  3156  	if op == nil {
  3157  		panic("reflect.Value.Convert: value of type " + v.typ.String() + " cannot be converted to type " + t.String())
  3158  	}
  3159  	return op(v, t)
  3160  }
  3161  
  3162  // CanConvert reports whether the value v can be converted to type t.
  3163  // If v.CanConvert(t) returns true then v.Convert(t) will not panic.
  3164  func (v Value) CanConvert(t Type) bool {
  3165  	vt := v.Type()
  3166  	if !vt.ConvertibleTo(t) {
  3167  		return false
  3168  	}
  3169  	// Currently the only conversion that is OK in terms of type
  3170  	// but that can panic depending on the value is converting
  3171  	// from slice to pointer-to-array.
  3172  	if vt.Kind() == Slice && t.Kind() == Pointer && t.Elem().Kind() == Array {
  3173  		n := t.Elem().Len()
  3174  		if n > v.Len() {
  3175  			return false
  3176  		}
  3177  	}
  3178  	return true
  3179  }
  3180  
  3181  // convertOp returns the function to convert a value of type src
  3182  // to a value of type dst. If the conversion is illegal, convertOp returns nil.
  3183  func convertOp(dst, src *rtype) func(Value, Type) Value {
  3184  	switch src.Kind() {
  3185  	case Int, Int8, Int16, Int32, Int64:
  3186  		switch dst.Kind() {
  3187  		case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  3188  			return cvtInt
  3189  		case Float32, Float64:
  3190  			return cvtIntFloat
  3191  		case String:
  3192  			return cvtIntString
  3193  		}
  3194  
  3195  	case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  3196  		switch dst.Kind() {
  3197  		case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  3198  			return cvtUint
  3199  		case Float32, Float64:
  3200  			return cvtUintFloat
  3201  		case String:
  3202  			return cvtUintString
  3203  		}
  3204  
  3205  	case Float32, Float64:
  3206  		switch dst.Kind() {
  3207  		case Int, Int8, Int16, Int32, Int64:
  3208  			return cvtFloatInt
  3209  		case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
  3210  			return cvtFloatUint
  3211  		case Float32, Float64:
  3212  			return cvtFloat
  3213  		}
  3214  
  3215  	case Complex64, Complex128:
  3216  		switch dst.Kind() {
  3217  		case Complex64, Complex128:
  3218  			return cvtComplex
  3219  		}
  3220  
  3221  	case String:
  3222  		if dst.Kind() == Slice && dst.Elem().PkgPath() == "" {
  3223  			switch dst.Elem().Kind() {
  3224  			case Uint8:
  3225  				return cvtStringBytes
  3226  			case Int32:
  3227  				return cvtStringRunes
  3228  			}
  3229  		}
  3230  
  3231  	case Slice:
  3232  		if dst.Kind() == String && src.Elem().PkgPath() == "" {
  3233  			switch src.Elem().Kind() {
  3234  			case Uint8:
  3235  				return cvtBytesString
  3236  			case Int32:
  3237  				return cvtRunesString
  3238  			}
  3239  		}
  3240  		// "x is a slice, T is a pointer-to-array type,
  3241  		// and the slice and array types have identical element types."
  3242  		if dst.Kind() == Pointer && dst.Elem().Kind() == Array && src.Elem() == dst.Elem().Elem() {
  3243  			return cvtSliceArrayPtr
  3244  		}
  3245  
  3246  	case Chan:
  3247  		if dst.Kind() == Chan && specialChannelAssignability(dst, src) {
  3248  			return cvtDirect
  3249  		}
  3250  	}
  3251  
  3252  	// dst and src have same underlying type.
  3253  	if haveIdenticalUnderlyingType(dst, src, false) {
  3254  		return cvtDirect
  3255  	}
  3256  
  3257  	// dst and src are non-defined pointer types with same underlying base type.
  3258  	if dst.Kind() == Pointer && dst.Name() == "" &&
  3259  		src.Kind() == Pointer && src.Name() == "" &&
  3260  		haveIdenticalUnderlyingType(dst.Elem().common(), src.Elem().common(), false) {
  3261  		return cvtDirect
  3262  	}
  3263  
  3264  	if implements(dst, src) {
  3265  		if src.Kind() == Interface {
  3266  			return cvtI2I
  3267  		}
  3268  		return cvtT2I
  3269  	}
  3270  
  3271  	return nil
  3272  }
  3273  
  3274  // makeInt returns a Value of type t equal to bits (possibly truncated),
  3275  // where t is a signed or unsigned int type.
  3276  func makeInt(f flag, bits uint64, t Type) Value {
  3277  	typ := t.common()
  3278  	ptr := unsafe_New(typ)
  3279  	switch typ.size {
  3280  	case 1:
  3281  		*(*uint8)(ptr) = uint8(bits)
  3282  	case 2:
  3283  		*(*uint16)(ptr) = uint16(bits)
  3284  	case 4:
  3285  		*(*uint32)(ptr) = uint32(bits)
  3286  	case 8:
  3287  		*(*uint64)(ptr) = bits
  3288  	}
  3289  	return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
  3290  }
  3291  
  3292  // makeFloat returns a Value of type t equal to v (possibly truncated to float32),
  3293  // where t is a float32 or float64 type.
  3294  func makeFloat(f flag, v float64, t Type) Value {
  3295  	typ := t.common()
  3296  	ptr := unsafe_New(typ)
  3297  	switch typ.size {
  3298  	case 4:
  3299  		*(*float32)(ptr) = float32(v)
  3300  	case 8:
  3301  		*(*float64)(ptr) = v
  3302  	}
  3303  	return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
  3304  }
  3305  
  3306  // makeFloat returns a Value of type t equal to v, where t is a float32 type.
  3307  func makeFloat32(f flag, v float32, t Type) Value {
  3308  	typ := t.common()
  3309  	ptr := unsafe_New(typ)
  3310  	*(*float32)(ptr) = v
  3311  	return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
  3312  }
  3313  
  3314  // makeComplex returns a Value of type t equal to v (possibly truncated to complex64),
  3315  // where t is a complex64 or complex128 type.
  3316  func makeComplex(f flag, v complex128, t Type) Value {
  3317  	typ := t.common()
  3318  	ptr := unsafe_New(typ)
  3319  	switch typ.size {
  3320  	case 8:
  3321  		*(*complex64)(ptr) = complex64(v)
  3322  	case 16:
  3323  		*(*complex128)(ptr) = v
  3324  	}
  3325  	return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
  3326  }
  3327  
  3328  func makeString(f flag, v string, t Type) Value {
  3329  	ret := New(t).Elem()
  3330  	ret.SetString(v)
  3331  	ret.flag = ret.flag&^flagAddr | f
  3332  	return ret
  3333  }
  3334  
  3335  func makeBytes(f flag, v []byte, t Type) Value {
  3336  	ret := New(t).Elem()
  3337  	ret.SetBytes(v)
  3338  	ret.flag = ret.flag&^flagAddr | f
  3339  	return ret
  3340  }
  3341  
  3342  func makeRunes(f flag, v []rune, t Type) Value {
  3343  	ret := New(t).Elem()
  3344  	ret.setRunes(v)
  3345  	ret.flag = ret.flag&^flagAddr | f
  3346  	return ret
  3347  }
  3348  
  3349  // These conversion functions are returned by convertOp
  3350  // for classes of conversions. For example, the first function, cvtInt,
  3351  // takes any value v of signed int type and returns the value converted
  3352  // to type t, where t is any signed or unsigned int type.
  3353  
  3354  // convertOp: intXX -> [u]intXX
  3355  func cvtInt(v Value, t Type) Value {
  3356  	return makeInt(v.flag.ro(), uint64(v.Int()), t)
  3357  }
  3358  
  3359  // convertOp: uintXX -> [u]intXX
  3360  func cvtUint(v Value, t Type) Value {
  3361  	return makeInt(v.flag.ro(), v.Uint(), t)
  3362  }
  3363  
  3364  // convertOp: floatXX -> intXX
  3365  func cvtFloatInt(v Value, t Type) Value {
  3366  	return makeInt(v.flag.ro(), uint64(int64(v.Float())), t)
  3367  }
  3368  
  3369  // convertOp: floatXX -> uintXX
  3370  func cvtFloatUint(v Value, t Type) Value {
  3371  	return makeInt(v.flag.ro(), uint64(v.Float()), t)
  3372  }
  3373  
  3374  // convertOp: intXX -> floatXX
  3375  func cvtIntFloat(v Value, t Type) Value {
  3376  	return makeFloat(v.flag.ro(), float64(v.Int()), t)
  3377  }
  3378  
  3379  // convertOp: uintXX -> floatXX
  3380  func cvtUintFloat(v Value, t Type) Value {
  3381  	return makeFloat(v.flag.ro(), float64(v.Uint()), t)
  3382  }
  3383  
  3384  // convertOp: floatXX -> floatXX
  3385  func cvtFloat(v Value, t Type) Value {
  3386  	if v.Type().Kind() == Float32 && t.Kind() == Float32 {
  3387  		// Don't do any conversion if both types have underlying type float32.
  3388  		// This avoids converting to float64 and back, which will
  3389  		// convert a signaling NaN to a quiet NaN. See issue 36400.
  3390  		return makeFloat32(v.flag.ro(), *(*float32)(v.ptr), t)
  3391  	}
  3392  	return makeFloat(v.flag.ro(), v.Float(), t)
  3393  }
  3394  
  3395  // convertOp: complexXX -> complexXX
  3396  func cvtComplex(v Value, t Type) Value {
  3397  	return makeComplex(v.flag.ro(), v.Complex(), t)
  3398  }
  3399  
  3400  // convertOp: intXX -> string
  3401  func cvtIntString(v Value, t Type) Value {
  3402  	s := "\uFFFD"
  3403  	if x := v.Int(); int64(rune(x)) == x {
  3404  		s = string(rune(x))
  3405  	}
  3406  	return makeString(v.flag.ro(), s, t)
  3407  }
  3408  
  3409  // convertOp: uintXX -> string
  3410  func cvtUintString(v Value, t Type) Value {
  3411  	s := "\uFFFD"
  3412  	if x := v.Uint(); uint64(rune(x)) == x {
  3413  		s = string(rune(x))
  3414  	}
  3415  	return makeString(v.flag.ro(), s, t)
  3416  }
  3417  
  3418  // convertOp: []byte -> string
  3419  func cvtBytesString(v Value, t Type) Value {
  3420  	return makeString(v.flag.ro(), string(v.Bytes()), t)
  3421  }
  3422  
  3423  // convertOp: string -> []byte
  3424  func cvtStringBytes(v Value, t Type) Value {
  3425  	return makeBytes(v.flag.ro(), []byte(v.String()), t)
  3426  }
  3427  
  3428  // convertOp: []rune -> string
  3429  func cvtRunesString(v Value, t Type) Value {
  3430  	return makeString(v.flag.ro(), string(v.runes()), t)
  3431  }
  3432  
  3433  // convertOp: string -> []rune
  3434  func cvtStringRunes(v Value, t Type) Value {
  3435  	return makeRunes(v.flag.ro(), []rune(v.String()), t)
  3436  }
  3437  
  3438  // convertOp: []T -> *[N]T
  3439  func cvtSliceArrayPtr(v Value, t Type) Value {
  3440  	n := t.Elem().Len()
  3441  	if n > v.Len() {
  3442  		panic("reflect: cannot convert slice with length " + itoa.Itoa(v.Len()) + " to pointer to array with length " + itoa.Itoa(n))
  3443  	}
  3444  	h := (*unsafeheader.Slice)(v.ptr)
  3445  	return Value{t.common(), h.Data, v.flag&^(flagIndir|flagAddr|flagKindMask) | flag(Pointer)}
  3446  }
  3447  
  3448  // convertOp: direct copy
  3449  func cvtDirect(v Value, typ Type) Value {
  3450  	f := v.flag
  3451  	t := typ.common()
  3452  	ptr := v.ptr
  3453  	if f&flagAddr != 0 {
  3454  		// indirect, mutable word - make a copy
  3455  		c := unsafe_New(t)
  3456  		typedmemmove(t, c, ptr)
  3457  		ptr = c
  3458  		f &^= flagAddr
  3459  	}
  3460  	return Value{t, ptr, v.flag.ro() | f} // v.flag.ro()|f == f?
  3461  }
  3462  
  3463  // convertOp: concrete -> interface
  3464  func cvtT2I(v Value, typ Type) Value {
  3465  	target := unsafe_New(typ.common())
  3466  	x := valueInterface(v, false)
  3467  	if typ.NumMethod() == 0 {
  3468  		*(*any)(target) = x
  3469  	} else {
  3470  		ifaceE2I(typ.(*rtype), x, target)
  3471  	}
  3472  	return Value{typ.common(), target, v.flag.ro() | flagIndir | flag(Interface)}
  3473  }
  3474  
  3475  // convertOp: interface -> interface
  3476  func cvtI2I(v Value, typ Type) Value {
  3477  	if v.IsNil() {
  3478  		ret := Zero(typ)
  3479  		ret.flag |= v.flag.ro()
  3480  		return ret
  3481  	}
  3482  	return cvtT2I(v.Elem(), typ)
  3483  }
  3484  
  3485  // implemented in ../runtime
  3486  func chancap(ch unsafe.Pointer) int
  3487  func chanclose(ch unsafe.Pointer)
  3488  func chanlen(ch unsafe.Pointer) int
  3489  
  3490  // Note: some of the noescape annotations below are technically a lie,
  3491  // but safe in the context of this package. Functions like chansend
  3492  // and mapassign don't escape the referent, but may escape anything
  3493  // the referent points to (they do shallow copies of the referent).
  3494  // It is safe in this package because the referent may only point
  3495  // to something a Value may point to, and that is always in the heap
  3496  // (due to the escapes() call in ValueOf).
  3497  
  3498  //go:noescape
  3499  func chanrecv(ch unsafe.Pointer, nb bool, val unsafe.Pointer) (selected, received bool)
  3500  
  3501  //go:noescape
  3502  func chansend(ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool
  3503  
  3504  func makechan(typ *rtype, size int) (ch unsafe.Pointer)
  3505  func makemap(t *rtype, cap int) (m unsafe.Pointer)
  3506  
  3507  //go:noescape
  3508  func mapaccess(t *rtype, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer)
  3509  
  3510  //go:noescape
  3511  func mapaccess_faststr(t *rtype, m unsafe.Pointer, key string) (val unsafe.Pointer)
  3512  
  3513  //go:noescape
  3514  func mapassign(t *rtype, m unsafe.Pointer, key, val unsafe.Pointer)
  3515  
  3516  //go:noescape
  3517  func mapassign_faststr(t *rtype, m unsafe.Pointer, key string, val unsafe.Pointer)
  3518  
  3519  //go:noescape
  3520  func mapdelete(t *rtype, m unsafe.Pointer, key unsafe.Pointer)
  3521  
  3522  //go:noescape
  3523  func mapdelete_faststr(t *rtype, m unsafe.Pointer, key string)
  3524  
  3525  //go:noescape
  3526  func mapiterinit(t *rtype, m unsafe.Pointer, it *hiter)
  3527  
  3528  //go:noescape
  3529  func mapiterkey(it *hiter) (key unsafe.Pointer)
  3530  
  3531  //go:noescape
  3532  func mapiterelem(it *hiter) (elem unsafe.Pointer)
  3533  
  3534  //go:noescape
  3535  func mapiternext(it *hiter)
  3536  
  3537  //go:noescape
  3538  func maplen(m unsafe.Pointer) int
  3539  
  3540  // call calls fn with "stackArgsSize" bytes of stack arguments laid out
  3541  // at stackArgs and register arguments laid out in regArgs. frameSize is
  3542  // the total amount of stack space that will be reserved by call, so this
  3543  // should include enough space to spill register arguments to the stack in
  3544  // case of preemption.
  3545  //
  3546  // After fn returns, call copies stackArgsSize-stackRetOffset result bytes
  3547  // back into stackArgs+stackRetOffset before returning, for any return
  3548  // values passed on the stack. Register-based return values will be found
  3549  // in the same regArgs structure.
  3550  //
  3551  // regArgs must also be prepared with an appropriate ReturnIsPtr bitmap
  3552  // indicating which registers will contain pointer-valued return values. The
  3553  // purpose of this bitmap is to keep pointers visible to the GC between
  3554  // returning from reflectcall and actually using them.
  3555  //
  3556  // If copying result bytes back from the stack, the caller must pass the
  3557  // argument frame type as stackArgsType, so that call can execute appropriate
  3558  // write barriers during the copy.
  3559  //
  3560  // Arguments passed through to call do not escape. The type is used only in a
  3561  // very limited callee of call, the stackArgs are copied, and regArgs is only
  3562  // used in the call frame.
  3563  //
  3564  //go:noescape
  3565  //go:linkname call runtime.reflectcall
  3566  func call(stackArgsType *rtype, f, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs)
  3567  
  3568  func ifaceE2I(t *rtype, src any, dst unsafe.Pointer)
  3569  
  3570  // memmove copies size bytes to dst from src. No write barriers are used.
  3571  //
  3572  //go:noescape
  3573  func memmove(dst, src unsafe.Pointer, size uintptr)
  3574  
  3575  // typedmemmove copies a value of type t to dst from src.
  3576  //
  3577  //go:noescape
  3578  func typedmemmove(t *rtype, dst, src unsafe.Pointer)
  3579  
  3580  // typedmemmovepartial is like typedmemmove but assumes that
  3581  // dst and src point off bytes into the value and only copies size bytes.
  3582  //
  3583  //go:noescape
  3584  func typedmemmovepartial(t *rtype, dst, src unsafe.Pointer, off, size uintptr)
  3585  
  3586  // typedmemclr zeros the value at ptr of type t.
  3587  //
  3588  //go:noescape
  3589  func typedmemclr(t *rtype, ptr unsafe.Pointer)
  3590  
  3591  // typedmemclrpartial is like typedmemclr but assumes that
  3592  // dst points off bytes into the value and only clears size bytes.
  3593  //
  3594  //go:noescape
  3595  func typedmemclrpartial(t *rtype, ptr unsafe.Pointer, off, size uintptr)
  3596  
  3597  // typedslicecopy copies a slice of elemType values from src to dst,
  3598  // returning the number of elements copied.
  3599  //
  3600  //go:noescape
  3601  func typedslicecopy(elemType *rtype, dst, src unsafeheader.Slice) int
  3602  
  3603  //go:noescape
  3604  func typehash(t *rtype, p unsafe.Pointer, h uintptr) uintptr
  3605  
  3606  func verifyNotInHeapPtr(p uintptr) bool
  3607  
  3608  // Dummy annotation marking that the value x escapes,
  3609  // for use in cases where the reflect code is so clever that
  3610  // the compiler cannot follow.
  3611  func escapes(x any) {
  3612  	if dummy.b {
  3613  		dummy.x = x
  3614  	}
  3615  }
  3616  
  3617  var dummy struct {
  3618  	b bool
  3619  	x any
  3620  }
  3621  

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