1 // Copyright 2010 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 rand implements a cryptographically secure 6 // random number generator. 7 package rand 8 9 import "io" 10 11 // Reader is a global, shared instance of a cryptographically 12 // secure random number generator. 13 // 14 // On Linux, FreeBSD, Dragonfly and Solaris, Reader uses getrandom(2) if 15 // available, /dev/urandom otherwise. 16 // On OpenBSD and macOS, Reader uses getentropy(2). 17 // On other Unix-like systems, Reader reads from /dev/urandom. 18 // On Windows systems, Reader uses the RtlGenRandom API. 19 // On Wasm, Reader uses the Web Crypto API. 20 var Reader io.Reader 21 22 // Read is a helper function that calls Reader.Read using io.ReadFull. 23 // On return, n == len(b) if and only if err == nil. 24 func Read(b []byte) (n int, err error) { 25 return io.ReadFull(Reader, b) 26 } 27 28 // batched returns a function that calls f to populate a []byte by chunking it 29 // into subslices of, at most, readMax bytes. 30 func batched(f func([]byte) error, readMax int) func([]byte) error { 31 return func(out []byte) error { 32 for len(out) > 0 { 33 read := len(out) 34 if read > readMax { 35 read = readMax 36 } 37 if err := f(out[:read]); err != nil { 38 return err 39 } 40 out = out[read:] 41 } 42 return nil 43 } 44 } 45