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moby--moby/pkg/ioutils/readers.go
Srini Brahmaroutu 7c52fcce85 goroutine fairness is not guaranteed causing the hang with GCCGO
Signed-off-by: Srini Brahmaroutu <srbrahma@us.ibm.com>
2015-09-25 14:40:16 +00:00

170 lines
3.3 KiB
Go

package ioutils
import (
"crypto/sha256"
"encoding/hex"
"io"
"sync"
)
type readCloserWrapper struct {
io.Reader
closer func() error
}
func (r *readCloserWrapper) Close() error {
return r.closer()
}
// NewReadCloserWrapper returns a new io.ReadCloser.
func NewReadCloserWrapper(r io.Reader, closer func() error) io.ReadCloser {
return &readCloserWrapper{
Reader: r,
closer: closer,
}
}
type readerErrWrapper struct {
reader io.Reader
closer func()
}
func (r *readerErrWrapper) Read(p []byte) (int, error) {
n, err := r.reader.Read(p)
if err != nil {
r.closer()
}
return n, err
}
// NewReaderErrWrapper returns a new io.Reader.
func NewReaderErrWrapper(r io.Reader, closer func()) io.Reader {
return &readerErrWrapper{
reader: r,
closer: closer,
}
}
// bufReader allows the underlying reader to continue to produce
// output by pre-emptively reading from the wrapped reader.
// This is achieved by buffering this data in bufReader's
// expanding buffer.
type bufReader struct {
sync.Mutex
buf io.ReadWriter
reader io.Reader
err error
wait sync.Cond
drainBuf []byte
}
// NewBufReader returns a new bufReader.
func NewBufReader(r io.Reader) io.ReadCloser {
reader := &bufReader{
buf: NewBytesPipe(nil),
reader: r,
drainBuf: make([]byte, 1024),
}
reader.wait.L = &reader.Mutex
go reader.drain()
return reader
}
// NewBufReaderWithDrainbufAndBuffer returns a BufReader with drainBuffer and buffer.
func NewBufReaderWithDrainbufAndBuffer(r io.Reader, drainBuffer []byte, buffer io.ReadWriter) io.ReadCloser {
reader := &bufReader{
buf: buffer,
drainBuf: drainBuffer,
reader: r,
}
reader.wait.L = &reader.Mutex
go reader.drain()
return reader
}
func (r *bufReader) drain() {
for {
//Call to scheduler is made to yield from this goroutine.
//This avoids goroutine looping here when n=0,err=nil, fixes code hangs when run with GCC Go.
callSchedulerIfNecessary()
n, err := r.reader.Read(r.drainBuf)
r.Lock()
if err != nil {
r.err = err
} else {
if n == 0 {
// nothing written, no need to signal
r.Unlock()
continue
}
r.buf.Write(r.drainBuf[:n])
}
r.wait.Signal()
r.Unlock()
if err != nil {
break
}
}
}
func (r *bufReader) Read(p []byte) (n int, err error) {
r.Lock()
defer r.Unlock()
for {
n, err = r.buf.Read(p)
if n > 0 {
return n, err
}
if r.err != nil {
return 0, r.err
}
r.wait.Wait()
}
}
// Close closes the bufReader
func (r *bufReader) Close() error {
closer, ok := r.reader.(io.ReadCloser)
if !ok {
return nil
}
return closer.Close()
}
// HashData returns the sha256 sum of src.
func HashData(src io.Reader) (string, error) {
h := sha256.New()
if _, err := io.Copy(h, src); err != nil {
return "", err
}
return "sha256:" + hex.EncodeToString(h.Sum(nil)), nil
}
// OnEOFReader wraps a io.ReadCloser and a function
// the function will run at the end of file or close the file.
type OnEOFReader struct {
Rc io.ReadCloser
Fn func()
}
func (r *OnEOFReader) Read(p []byte) (n int, err error) {
n, err = r.Rc.Read(p)
if err == io.EOF {
r.runFunc()
}
return
}
// Close closes the file and run the function.
func (r *OnEOFReader) Close() error {
err := r.Rc.Close()
r.runFunc()
return err
}
func (r *OnEOFReader) runFunc() {
if fn := r.Fn; fn != nil {
fn()
r.Fn = nil
}
}