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add DialExisting #35

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add DialExisting #35

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42 changes: 30 additions & 12 deletions npipe_windows.go
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Original file line number Diff line number Diff line change
Expand Up @@ -103,27 +103,45 @@ func (e PipeError) Temporary() bool {
// Dial will return a PipeError if you pass in a badly formatted pipe name.
//
// Examples:
// // local pipe
// conn, err := Dial(`\\.\pipe\mypipename`)
//
// // remote pipe
// conn, err := Dial(`\\othercomp\pipe\mypipename`)
// // local pipe
// conn, err := Dial(`\\.\pipe\mypipename`)
//
// // remote pipe
// conn, err := Dial(`\\othercomp\pipe\mypipename`)
func Dial(address string) (*PipeConn, error) {
return dialImpl(address, true)
}

// DialExisting acts like Dial but fails right away if the pipe doesn't exist
func DialExisting(address string) (*PipeConn, error) {
return dialImpl(address, false)
}

// DialTimeout acts like Dial, but will time out after the duration of timeout
func DialTimeout(address string, timeout time.Duration) (*PipeConn, error) {
return dialTimeoutImpl(address, timeout, true)
}

// DialTimeoutExisting acts like DialTimeout but fails right away if the pipe doesn't exist
func DialTimeoutExisting(address string, timeout time.Duration) (*PipeConn, error) {
return dialTimeoutImpl(address, timeout, false)
}

func dialImpl(address string, waitForPipe bool) (*PipeConn, error) {
for {
conn, err := dial(address, nmpwait_wait_forever)
if err == nil {
return conn, nil
}
if isPipeNotReady(err) {
if isPipeNotReady(err, waitForPipe) {
<-time.After(100 * time.Millisecond)
continue
}
return nil, err
}
}

// DialTimeout acts like Dial, but will time out after the duration of timeout
func DialTimeout(address string, timeout time.Duration) (*PipeConn, error) {
func dialTimeoutImpl(address string, timeout time.Duration, waitForPipe bool) (*PipeConn, error) {
deadline := time.Now().Add(timeout)

now := time.Now()
Expand All @@ -138,7 +156,7 @@ func DialTimeout(address string, timeout time.Duration) (*PipeConn, error) {
return nil, PipeError{fmt.Sprintf(
"Timed out waiting for pipe '%s' to come available", address), true}
}
if isPipeNotReady(err) {
if isPipeNotReady(err, waitForPipe) {
left := deadline.Sub(time.Now())
retry := 100 * time.Millisecond
if left > retry {
Expand All @@ -156,13 +174,13 @@ func DialTimeout(address string, timeout time.Duration) (*PipeConn, error) {
}

// isPipeNotReady checks the error to see if it indicates the pipe is not ready
func isPipeNotReady(err error) bool {
func isPipeNotReady(err error, waitForPipe bool) bool {
// Pipe Busy means another client just grabbed the open pipe end,
// and the server hasn't made a new one yet.
// File Not Found means the server hasn't created the pipe yet.
// Neither is a fatal error.
// If waitForPipe is false, File Not Found is treated as fatal

return err == syscall.ERROR_FILE_NOT_FOUND || err == error_pipe_busy
return (waitForPipe && err == syscall.ERROR_FILE_NOT_FOUND) || err == error_pipe_busy
}

// newOverlapped creates a structure used to track asynchronous
Expand Down