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