// Created by cgo -godefs - DO NOT EDIT
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// cgo -godefs sem_linux.go
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package shm
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import (
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"sync/atomic"
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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type Semaphore [32]byte
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type newSem struct {
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Value uint32
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Private int32
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NWaiters uint64
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}
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func New(value uint) (*Semaphore, error) {
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sem := new(Semaphore)
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if err := sem.Init(value); err != nil {
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return nil, err
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}
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return sem, nil
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}
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func atomicDecrementIfPositive(mem *uint32) uint32 {
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for {
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if old := atomic.LoadUint32(mem); old == 0 || atomic.CompareAndSwapUint32(mem, old, old-1) {
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return old
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}
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}
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}
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func (sem *Semaphore) Wait() error {
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isem := (*newSem)(unsafe.Pointer(sem))
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if atomicDecrementIfPositive(&isem.Value) > 0 {
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return nil
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}
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atomic.AddUint64(&isem.NWaiters, 1)
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for {
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t := syscall.Timeval{3 /*sec*/, 0 /*usec*/}
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if _, _, err := unix.Syscall6(unix.SYS_FUTEX, uintptr(unsafe.Pointer(&isem.Value)), uintptr(0x0), 0, uintptr(unsafe.Pointer(&t)), 0, 0); err != 0 && err != unix.EWOULDBLOCK {
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atomic.AddUint64(&isem.NWaiters, ^uint64(0))
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return err
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}
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if atomicDecrementIfPositive(&isem.Value) > 0 {
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atomic.AddUint64(&isem.NWaiters, ^uint64(0))
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return nil
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}
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}
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}
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func (sem *Semaphore) TryWait() error {
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isem := (*newSem)(unsafe.Pointer(sem))
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if atomicDecrementIfPositive(&isem.Value) > 0 {
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return nil
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}
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return unix.EAGAIN
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}
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func (sem *Semaphore) Post() error {
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isem := (*newSem)(unsafe.Pointer(sem))
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for {
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cur := atomic.LoadUint32(&isem.Value)
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if cur == 0x7fffffff {
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return unix.EOVERFLOW
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}
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if atomic.CompareAndSwapUint32(&isem.Value, cur, cur+1) {
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break
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}
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}
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if atomic.LoadUint64(&isem.NWaiters) <= 0 {
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return nil
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}
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if _, _, err := unix.Syscall6(unix.SYS_FUTEX, uintptr(unsafe.Pointer(&isem.Value)), uintptr(0x1), 1, 0, 0, 0); err != 0 {
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return err
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}
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return nil
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}
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func (sem *Semaphore) Init(value uint) error {
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if value > 0x7fffffff {
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return unix.EINVAL
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}
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isem := (*newSem)(unsafe.Pointer(sem))
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isem.Value = uint32(value)
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isem.Private = 0
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isem.NWaiters = 0
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return nil
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}
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func (sem *Semaphore) Destroy() error {
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return nil
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}
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