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package winio
import (
"errors"
"io"
"runtime"
"sync"
"syscall"
"time"
)
//sys cancelIoEx(file syscall.Handle, o *syscall.Overlapped) (err error) = CancelIoEx
//sys createIoCompletionPort(file syscall.Handle, port syscall.Handle, key uintptr, threadCount uint32) (newport syscall.Handle, err error) = CreateIoCompletionPort
//sys getQueuedCompletionStatus(port syscall.Handle, bytes *uint32, key *uintptr, o **ioOperation, timeout uint32) (err error) = GetQueuedCompletionStatus
//sys setFileCompletionNotificationModes(h syscall.Handle, flags uint8) (err error) = SetFileCompletionNotificationModes
//sys timeBeginPeriod(period uint32) (n int32) = winmm.timeBeginPeriod
const (
cFILE_SKIP_COMPLETION_PORT_ON_SUCCESS = 1
cFILE_SKIP_SET_EVENT_ON_HANDLE = 2
)
var (
ErrFileClosed = errors.New("file has already been closed")
ErrTimeout = &timeoutError{}
)
type timeoutError struct{}
func (e *timeoutError) Error() string { return "i/o timeout" }
func (e *timeoutError) Timeout() bool { return true }
func (e *timeoutError) Temporary() bool { return true }
var ioInitOnce sync.Once
var ioCompletionPort syscall.Handle
// ioResult contains the result of an asynchronous IO operation
type ioResult struct {
bytes uint32
err error
}
// ioOperation represents an outstanding asynchronous Win32 IO
type ioOperation struct {
o syscall.Overlapped
ch chan ioResult
}
func initIo() {
h, err := createIoCompletionPort(syscall.InvalidHandle, 0, 0, 0xffffffff)
if err != nil {
panic(err)
}
ioCompletionPort = h
go ioCompletionProcessor(h)
}
// win32File implements Reader, Writer, and Closer on a Win32 handle without blocking in a syscall.
// It takes ownership of this handle and will close it if it is garbage collected.
type win32File struct {
handle syscall.Handle
wg sync.WaitGroup
closing bool
readDeadline time.Time
writeDeadline time.Time
}
// makeWin32File makes a new win32File from an existing file handle
func makeWin32File(h syscall.Handle) (*win32File, error) {
f := &win32File{handle: h}
ioInitOnce.Do(initIo)
_, err := createIoCompletionPort(h, ioCompletionPort, 0, 0xffffffff)
if err != nil {
return nil, err
}
err = setFileCompletionNotificationModes(h, cFILE_SKIP_COMPLETION_PORT_ON_SUCCESS|cFILE_SKIP_SET_EVENT_ON_HANDLE)
if err != nil {
return nil, err
}
runtime.SetFinalizer(f, (*win32File).closeHandle)
return f, nil
}
func MakeOpenFile(h syscall.Handle) (io.ReadWriteCloser, error) {
return makeWin32File(h)
}
// closeHandle closes the resources associated with a Win32 handle
func (f *win32File) closeHandle() {
if !f.closing {
// cancel all IO and wait for it to complete
f.closing = true
cancelIoEx(f.handle, nil)
f.wg.Wait()
// at this point, no new IO can start
syscall.Close(f.handle)
f.handle = 0
}
}
// Close closes a win32File.
func (f *win32File) Close() error {
f.closeHandle()
runtime.SetFinalizer(f, nil)
return nil
}
// prepareIo prepares for a new IO operation
func (f *win32File) prepareIo() (*ioOperation, error) {
f.wg.Add(1)
if f.closing {
return nil, ErrFileClosed
}
c := &ioOperation{}
c.ch = make(chan ioResult)
return c, nil
}
// ioCompletionProcessor processes completed async IOs forever
func ioCompletionProcessor(h syscall.Handle) {
// Set the timer resolution to 1. This fixes a performance regression in golang 1.6.
timeBeginPeriod(1)
for {
var bytes uint32
var key uintptr
var op *ioOperation
err := getQueuedCompletionStatus(h, &bytes, &key, &op, syscall.INFINITE)
if op == nil {
panic(err)
}
op.ch <- ioResult{bytes, err}
}
}
// asyncIo processes the return value from ReadFile or WriteFile, blocking until
// the operation has actually completed.
func (f *win32File) asyncIo(c *ioOperation, deadline time.Time, bytes uint32, err error) (int, error) {
if err != syscall.ERROR_IO_PENDING {
f.wg.Done()
return int(bytes), err
} else {
var r ioResult
wait := true
timedout := false
if f.closing {
cancelIoEx(f.handle, &c.o)
} else if !deadline.IsZero() {
now := time.Now()
if !deadline.After(now) {
timedout = true
} else {
timeout := time.After(deadline.Sub(now))
select {
case r = <-c.ch:
wait = false
case <-timeout:
timedout = true
}
}
}
if timedout {
cancelIoEx(f.handle, &c.o)
}
if wait {
r = <-c.ch
}
err = r.err
if err == syscall.ERROR_OPERATION_ABORTED {
if f.closing {
err = ErrFileClosed
} else if timedout {
err = ErrTimeout
}
}
f.wg.Done()
return int(r.bytes), err
}
}
// Read reads from a file handle.
func (f *win32File) Read(b []byte) (int, error) {
c, err := f.prepareIo()
if err != nil {
return 0, err
}
var bytes uint32
err = syscall.ReadFile(f.handle, b, &bytes, &c.o)
n, err := f.asyncIo(c, f.readDeadline, bytes, err)
// Handle EOF conditions.
if err == nil && n == 0 && len(b) != 0 {
return 0, io.EOF
} else if err == syscall.ERROR_BROKEN_PIPE {
return 0, io.EOF
} else {
return n, err
}
}
// Write writes to a file handle.
func (f *win32File) Write(b []byte) (int, error) {
c, err := f.prepareIo()
if err != nil {
return 0, err
}
var bytes uint32
err = syscall.WriteFile(f.handle, b, &bytes, &c.o)
return f.asyncIo(c, f.writeDeadline, bytes, err)
}
func (f *win32File) SetReadDeadline(t time.Time) error {
f.readDeadline = t
return nil
}
func (f *win32File) SetWriteDeadline(t time.Time) error {
f.writeDeadline = t
return nil
}
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