kesavand | c71914f | 2022-03-25 11:19:03 +0530 | [diff] [blame] | 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 ( |
| 11 | "unsafe" |
| 12 | |
| 13 | "golang.org/x/sys/internal/unsafeheader" |
| 14 | ) |
| 15 | |
| 16 | // SysvShmAttach attaches the Sysv shared memory segment associated with the |
| 17 | // shared memory identifier id. |
| 18 | func SysvShmAttach(id int, addr uintptr, flag int) ([]byte, error) { |
| 19 | addr, errno := shmat(id, addr, flag) |
| 20 | if errno != nil { |
| 21 | return nil, errno |
| 22 | } |
| 23 | |
| 24 | // Retrieve the size of the shared memory to enable slice creation |
| 25 | var info SysvShmDesc |
| 26 | |
| 27 | _, err := SysvShmCtl(id, IPC_STAT, &info) |
| 28 | if err != nil { |
| 29 | // release the shared memory if we can't find the size |
| 30 | |
| 31 | // ignoring error from shmdt as there's nothing sensible to return here |
| 32 | shmdt(addr) |
| 33 | return nil, err |
| 34 | } |
| 35 | |
| 36 | // Use unsafe to convert addr into a []byte. |
| 37 | // TODO: convert to unsafe.Slice once we can assume Go 1.17 |
| 38 | var b []byte |
| 39 | hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b)) |
| 40 | hdr.Data = unsafe.Pointer(addr) |
| 41 | hdr.Cap = int(info.Segsz) |
| 42 | hdr.Len = int(info.Segsz) |
| 43 | return b, nil |
| 44 | } |
| 45 | |
| 46 | // SysvShmDetach unmaps the shared memory slice returned from SysvShmAttach. |
| 47 | // |
| 48 | // It is not safe to use the slice after calling this function. |
| 49 | func SysvShmDetach(data []byte) error { |
| 50 | if len(data) == 0 { |
| 51 | return EINVAL |
| 52 | } |
| 53 | |
| 54 | return shmdt(uintptr(unsafe.Pointer(&data[0]))) |
| 55 | } |
| 56 | |
| 57 | // SysvShmGet returns the Sysv shared memory identifier associated with key. |
| 58 | // If the IPC_CREAT flag is specified a new segment is created. |
| 59 | func SysvShmGet(key, size, flag int) (id int, err error) { |
| 60 | return shmget(key, size, flag) |
| 61 | } |