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1 // Copyright 2021 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 //go:build (darwin && !ios) || linux
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6 // +build darwin,!ios linux
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7
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8 package unix
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9
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68
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10 import "unsafe"
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66
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11
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12 // SysvShmAttach attaches the Sysv shared memory segment associated with the
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13 // shared memory identifier id.
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14 func SysvShmAttach(id int, addr uintptr, flag int) ([]byte, error) {
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15 addr, errno := shmat(id, addr, flag)
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16 if errno != nil {
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17 return nil, errno
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18 }
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19
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20 // Retrieve the size of the shared memory to enable slice creation
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21 var info SysvShmDesc
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22
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23 _, err := SysvShmCtl(id, IPC_STAT, &info)
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24 if err != nil {
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25 // release the shared memory if we can't find the size
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26
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27 // ignoring error from shmdt as there's nothing sensible to return here
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28 shmdt(addr)
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29 return nil, err
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30 }
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31
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32 // Use unsafe to convert addr into a []byte.
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33 b := unsafe.Slice((*byte)(unsafe.Pointer(addr)), int(info.Segsz))
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34 return b, nil
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35 }
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36
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37 // SysvShmDetach unmaps the shared memory slice returned from SysvShmAttach.
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38 //
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39 // It is not safe to use the slice after calling this function.
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40 func SysvShmDetach(data []byte) error {
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41 if len(data) == 0 {
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42 return EINVAL
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43 }
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44
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45 return shmdt(uintptr(unsafe.Pointer(&data[0])))
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46 }
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47
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48 // SysvShmGet returns the Sysv shared memory identifier associated with key.
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49 // If the IPC_CREAT flag is specified a new segment is created.
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50 func SysvShmGet(key, size, flag int) (id int, err error) {
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51 return shmget(key, size, flag)
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52 }
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