1 // Copyright 2021 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 //go:build (darwin && !ios) || linux 6 // +build darwin,!ios linux 7 8 package unix 9 10 import "unsafe" 11 12 // SysvShmAttach attaches the Sysv shared memory segment associated with the 13 // shared memory identifier id. 14 func SysvShmAttach(id int, addr uintptr, flag int) ([]byte, error) { 15 addr, errno := shmat(id, addr, flag) 16 if errno != nil { 17 return nil, errno 18 } 19 20 // Retrieve the size of the shared memory to enable slice creation 21 var info SysvShmDesc 22 23 _, err := SysvShmCtl(id, IPC_STAT, &info) 24 if err != nil { 25 // release the shared memory if we can't find the size 26 27 // ignoring error from shmdt as there's nothing sensible to return here 28 shmdt(addr) 29 return nil, err 30 } 31 32 // Use unsafe to convert addr into a []byte. 33 b := unsafe.Slice((*byte)(unsafe.Pointer(addr)), int(info.Segsz)) 34 return b, nil 35 } 36 37 // SysvShmDetach unmaps the shared memory slice returned from SysvShmAttach. 38 // 39 // It is not safe to use the slice after calling this function. 40 func SysvShmDetach(data []byte) error { 41 if len(data) == 0 { 42 return EINVAL 43 } 44 45 return shmdt(uintptr(unsafe.Pointer(&data[0]))) 46 } 47 48 // SysvShmGet returns the Sysv shared memory identifier associated with key. 49 // If the IPC_CREAT flag is specified a new segment is created. 50 func SysvShmGet(key, size, flag int) (id int, err error) { 51 return shmget(key, size, flag) 52 } 53