296 lines
7 KiB
Go
296 lines
7 KiB
Go
// +build windows
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package winio
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import (
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"errors"
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"io"
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"runtime"
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"sync"
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"sync/atomic"
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"syscall"
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"time"
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)
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//sys cancelIoEx(file syscall.Handle, o *syscall.Overlapped) (err error) = CancelIoEx
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//sys createIoCompletionPort(file syscall.Handle, port syscall.Handle, key uintptr, threadCount uint32) (newport syscall.Handle, err error) = CreateIoCompletionPort
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//sys getQueuedCompletionStatus(port syscall.Handle, bytes *uint32, key *uintptr, o **ioOperation, timeout uint32) (err error) = GetQueuedCompletionStatus
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//sys setFileCompletionNotificationModes(h syscall.Handle, flags uint8) (err error) = SetFileCompletionNotificationModes
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//sys timeBeginPeriod(period uint32) (n int32) = winmm.timeBeginPeriod
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type atomicBool int32
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func (b *atomicBool) isSet() bool { return atomic.LoadInt32((*int32)(b)) != 0 }
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func (b *atomicBool) setFalse() { atomic.StoreInt32((*int32)(b), 0) }
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func (b *atomicBool) setTrue() { atomic.StoreInt32((*int32)(b), 1) }
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const (
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cFILE_SKIP_COMPLETION_PORT_ON_SUCCESS = 1
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cFILE_SKIP_SET_EVENT_ON_HANDLE = 2
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)
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var (
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ErrFileClosed = errors.New("file has already been closed")
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ErrTimeout = &timeoutError{}
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)
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type timeoutError struct{}
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func (e *timeoutError) Error() string { return "i/o timeout" }
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func (e *timeoutError) Timeout() bool { return true }
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func (e *timeoutError) Temporary() bool { return true }
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type timeoutChan chan struct{}
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var ioInitOnce sync.Once
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var ioCompletionPort syscall.Handle
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// ioResult contains the result of an asynchronous IO operation
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type ioResult struct {
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bytes uint32
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err error
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}
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// ioOperation represents an outstanding asynchronous Win32 IO
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type ioOperation struct {
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o syscall.Overlapped
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ch chan ioResult
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}
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func initIo() {
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h, err := createIoCompletionPort(syscall.InvalidHandle, 0, 0, 0xffffffff)
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if err != nil {
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panic(err)
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}
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ioCompletionPort = h
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go ioCompletionProcessor(h)
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}
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// win32File implements Reader, Writer, and Closer on a Win32 handle without blocking in a syscall.
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// It takes ownership of this handle and will close it if it is garbage collected.
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type win32File struct {
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handle syscall.Handle
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wg sync.WaitGroup
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closing bool
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readDeadline deadlineHandler
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writeDeadline deadlineHandler
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}
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type deadlineHandler struct {
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setLock sync.Mutex
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channel timeoutChan
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channelLock sync.RWMutex
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timer *time.Timer
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timedout atomicBool
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}
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// makeWin32File makes a new win32File from an existing file handle
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func makeWin32File(h syscall.Handle) (*win32File, error) {
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f := &win32File{handle: h}
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ioInitOnce.Do(initIo)
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_, err := createIoCompletionPort(h, ioCompletionPort, 0, 0xffffffff)
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if err != nil {
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return nil, err
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}
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err = setFileCompletionNotificationModes(h, cFILE_SKIP_COMPLETION_PORT_ON_SUCCESS|cFILE_SKIP_SET_EVENT_ON_HANDLE)
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if err != nil {
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return nil, err
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}
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f.readDeadline.channel = make(timeoutChan)
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f.writeDeadline.channel = make(timeoutChan)
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return f, nil
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}
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func MakeOpenFile(h syscall.Handle) (io.ReadWriteCloser, error) {
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return makeWin32File(h)
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}
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// closeHandle closes the resources associated with a Win32 handle
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func (f *win32File) closeHandle() {
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if !f.closing {
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// cancel all IO and wait for it to complete
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f.closing = true
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cancelIoEx(f.handle, nil)
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f.wg.Wait()
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// at this point, no new IO can start
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syscall.Close(f.handle)
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f.handle = 0
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}
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}
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// Close closes a win32File.
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func (f *win32File) Close() error {
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f.closeHandle()
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return nil
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}
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// prepareIo prepares for a new IO operation.
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// The caller must call f.wg.Done() when the IO is finished, prior to Close() returning.
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func (f *win32File) prepareIo() (*ioOperation, error) {
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f.wg.Add(1)
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if f.closing {
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return nil, ErrFileClosed
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}
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c := &ioOperation{}
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c.ch = make(chan ioResult)
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return c, nil
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}
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// ioCompletionProcessor processes completed async IOs forever
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func ioCompletionProcessor(h syscall.Handle) {
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// Set the timer resolution to 1. This fixes a performance regression in golang 1.6.
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timeBeginPeriod(1)
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for {
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var bytes uint32
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var key uintptr
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var op *ioOperation
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err := getQueuedCompletionStatus(h, &bytes, &key, &op, syscall.INFINITE)
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if op == nil {
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panic(err)
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}
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op.ch <- ioResult{bytes, err}
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}
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}
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// asyncIo processes the return value from ReadFile or WriteFile, blocking until
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// the operation has actually completed.
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func (f *win32File) asyncIo(c *ioOperation, d *deadlineHandler, bytes uint32, err error) (int, error) {
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if err != syscall.ERROR_IO_PENDING {
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return int(bytes), err
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}
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if f.closing {
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cancelIoEx(f.handle, &c.o)
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}
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var timeout timeoutChan
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if d != nil {
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d.channelLock.Lock()
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timeout = d.channel
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d.channelLock.Unlock()
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}
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var r ioResult
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select {
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case r = <-c.ch:
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err = r.err
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if err == syscall.ERROR_OPERATION_ABORTED {
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if f.closing {
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err = ErrFileClosed
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}
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}
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case <-timeout:
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cancelIoEx(f.handle, &c.o)
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r = <-c.ch
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err = r.err
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if err == syscall.ERROR_OPERATION_ABORTED {
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err = ErrTimeout
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}
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}
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// runtime.KeepAlive is needed, as c is passed via native
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// code to ioCompletionProcessor, c must remain alive
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// until the channel read is complete.
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runtime.KeepAlive(c)
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return int(r.bytes), err
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}
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// Read reads from a file handle.
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func (f *win32File) Read(b []byte) (int, error) {
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c, err := f.prepareIo()
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if err != nil {
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return 0, err
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}
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defer f.wg.Done()
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if f.readDeadline.timedout.isSet() {
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return 0, ErrTimeout
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}
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var bytes uint32
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err = syscall.ReadFile(f.handle, b, &bytes, &c.o)
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n, err := f.asyncIo(c, &f.readDeadline, bytes, err)
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runtime.KeepAlive(b)
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// Handle EOF conditions.
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if err == nil && n == 0 && len(b) != 0 {
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return 0, io.EOF
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} else if err == syscall.ERROR_BROKEN_PIPE {
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return 0, io.EOF
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} else {
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return n, err
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}
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}
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// Write writes to a file handle.
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func (f *win32File) Write(b []byte) (int, error) {
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c, err := f.prepareIo()
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if err != nil {
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return 0, err
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}
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defer f.wg.Done()
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if f.writeDeadline.timedout.isSet() {
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return 0, ErrTimeout
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}
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var bytes uint32
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err = syscall.WriteFile(f.handle, b, &bytes, &c.o)
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n, err := f.asyncIo(c, &f.writeDeadline, bytes, err)
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runtime.KeepAlive(b)
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return n, err
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}
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func (f *win32File) SetReadDeadline(deadline time.Time) error {
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return f.readDeadline.set(deadline)
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}
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func (f *win32File) SetWriteDeadline(deadline time.Time) error {
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return f.writeDeadline.set(deadline)
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}
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func (f *win32File) Flush() error {
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return syscall.FlushFileBuffers(f.handle)
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}
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func (d *deadlineHandler) set(deadline time.Time) error {
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d.setLock.Lock()
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defer d.setLock.Unlock()
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if d.timer != nil {
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if !d.timer.Stop() {
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<-d.channel
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}
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d.timer = nil
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}
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d.timedout.setFalse()
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select {
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case <-d.channel:
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d.channelLock.Lock()
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d.channel = make(chan struct{})
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d.channelLock.Unlock()
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default:
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}
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if deadline.IsZero() {
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return nil
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}
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timeoutIO := func() {
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d.timedout.setTrue()
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close(d.channel)
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}
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now := time.Now()
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duration := deadline.Sub(now)
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if deadline.After(now) {
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// Deadline is in the future, set a timer to wait
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d.timer = time.AfterFunc(duration, timeoutIO)
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} else {
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// Deadline is in the past. Cancel all pending IO now.
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timeoutIO()
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}
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return nil
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}
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