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