mirror of
https://github.com/golang/go
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d2a9e7164e
This CL moves code from code.google.com/p/dvyukov-go-perf-dashboard, which was previously reviewed. LGTM=adg R=adg CC=golang-codereviews https://golang.org/cl/95190043
106 lines
2.6 KiB
Go
106 lines
2.6 KiB
Go
// Copyright 2013 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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package main
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import (
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"sync"
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"syscall"
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"unsafe"
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)
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var (
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modkernel32 = syscall.NewLazyDLL("kernel32.dll")
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procLockFileEx = modkernel32.NewProc("LockFileEx")
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procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
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)
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const (
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INVALID_FILE_HANDLE = ^syscall.Handle(0)
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LOCKFILE_EXCLUSIVE_LOCK = 2
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)
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func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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r1, _, e1 := syscall.Syscall6(procLockFileEx.Addr(), 6, uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
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if r1 == 0 {
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if e1 != 0 {
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err = error(e1)
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} else {
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err = syscall.EINVAL
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}
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}
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return
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}
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func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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r1, _, e1 := syscall.Syscall6(procUnlockFileEx.Addr(), 5, uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
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if r1 == 0 {
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if e1 != 0 {
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err = error(e1)
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} else {
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err = syscall.EINVAL
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}
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}
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return
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}
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// FileMutex is similar to sync.RWMutex, but also synchronizes across processes.
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// This implementation is based on flock syscall.
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type FileMutex struct {
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mu sync.RWMutex
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fd syscall.Handle
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}
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func MakeFileMutex(filename string) *FileMutex {
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if filename == "" {
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return &FileMutex{fd: INVALID_FILE_HANDLE}
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}
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fd, err := syscall.CreateFile(&(syscall.StringToUTF16(filename)[0]), syscall.GENERIC_READ|syscall.GENERIC_WRITE,
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syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE, nil, syscall.OPEN_ALWAYS, syscall.FILE_ATTRIBUTE_NORMAL, 0)
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if err != nil {
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panic(err)
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}
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return &FileMutex{fd: fd}
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}
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func (m *FileMutex) Lock() {
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m.mu.Lock()
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if m.fd != INVALID_FILE_HANDLE {
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var ol syscall.Overlapped
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if err := lockFileEx(m.fd, LOCKFILE_EXCLUSIVE_LOCK, 0, 1, 0, &ol); err != nil {
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panic(err)
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}
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}
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}
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func (m *FileMutex) Unlock() {
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if m.fd != INVALID_FILE_HANDLE {
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var ol syscall.Overlapped
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if err := unlockFileEx(m.fd, 0, 1, 0, &ol); err != nil {
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panic(err)
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}
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}
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m.mu.Unlock()
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}
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func (m *FileMutex) RLock() {
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m.mu.RLock()
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if m.fd != INVALID_FILE_HANDLE {
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var ol syscall.Overlapped
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if err := lockFileEx(m.fd, 0, 0, 1, 0, &ol); err != nil {
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panic(err)
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}
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}
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}
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func (m *FileMutex) RUnlock() {
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if m.fd != INVALID_FILE_HANDLE {
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var ol syscall.Overlapped
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if err := unlockFileEx(m.fd, 0, 1, 0, &ol); err != nil {
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panic(err)
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}
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}
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m.mu.RUnlock()
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}
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