cubefs

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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build (darwin && !ios) || linux
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// +build darwin,!ios linux
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package unix
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import "unsafe"
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// SysvShmAttach attaches the Sysv shared memory segment associated with the
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// shared memory identifier id.
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func SysvShmAttach(id int, addr uintptr, flag int) ([]byte, error) {
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	addr, errno := shmat(id, addr, flag)
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	if errno != nil {
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		return nil, errno
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	}
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	// Retrieve the size of the shared memory to enable slice creation
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	var info SysvShmDesc
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	_, err := SysvShmCtl(id, IPC_STAT, &info)
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	if err != nil {
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		// release the shared memory if we can't find the size
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		// ignoring error from shmdt as there's nothing sensible to return here
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		shmdt(addr)
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		return nil, err
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	}
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	// Use unsafe to convert addr into a []byte.
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	b := unsafe.Slice((*byte)(unsafe.Pointer(addr)), int(info.Segsz))
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	return b, nil
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}
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// SysvShmDetach unmaps the shared memory slice returned from SysvShmAttach.
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//
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// It is not safe to use the slice after calling this function.
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func SysvShmDetach(data []byte) error {
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	if len(data) == 0 {
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		return EINVAL
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	}
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	return shmdt(uintptr(unsafe.Pointer(&data[0])))
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}
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// SysvShmGet returns the Sysv shared memory identifier associated with key.
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// If the IPC_CREAT flag is specified a new segment is created.
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func SysvShmGet(key, size, flag int) (id int, err error) {
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	return shmget(key, size, flag)
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}
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