increase buffer on RangeReadSeekCloser, synchronize read + buffer teardowns

http.go

@@ -6,20 +6,21 @@ import (
 	"io"
 	"net/http"
 	"net/url"
-	"runtime"
 	"strconv"
+	"sync"
 )
 
-const rangeReaderBufferSize = 4096
+const rangeReaderBufferSize = 1024 * 16
 
 type RangeReadSeekCloser struct {
-	uri    *url.URL
-	size   int64
-	i      int64
-	body   io.ReadCloser
-	buf    []byte
-	ib     int64
-	closed bool
+	uri          *url.URL
+	size         int64
+	readOffset   int64
+	body         io.ReadCloser
+	bodyLock     sync.RWMutex
+	buf          []byte
+	bufferOffset int64
+	closed       bool
 }
 
 func NewRangeReadSeekCloser(uri string) (*RangeReadSeekCloser, error) {
@@ -29,7 +30,6 @@ func NewRangeReadSeekCloser(uri string) (*RangeReadSeekCloser, error) {
 	}
 	r := &RangeReadSeekCloser{
 		uri: parsedUrl,
-		buf: make([]byte, 0, rangeReaderBufferSize),
 	}
 
 	if err = r.getInformation(); err != nil {
@@ -44,12 +44,14 @@ func (r *RangeReadSeekCloser) GetURI() string {
 }
 
 func (r *RangeReadSeekCloser) retryConnect() error {
+	r.bodyLock.Lock()
+	defer r.bodyLock.Unlock()
 	if r.closed {
 		return errors.New("already closed")
 	}
 
 	headers := make(http.Header)
-	startOffset := r.i
+	startOffset := r.readOffset
 
 	expectedLength := r.size - startOffset
 	headers.Set("Range", fmt.Sprintf("bytes=%d-", startOffset))
@@ -63,7 +65,6 @@ func (r *RangeReadSeekCloser) retryConnect() error {
 		return err
 	}
 	r.body = response.Body
-	runtime.SetFinalizer(r.body, io.ReadCloser.Close)
 
 	if response.StatusCode != http.StatusPartialContent {
 		r.body.Close()
@@ -88,23 +89,37 @@ func (r *RangeReadSeekCloser) retryConnect() error {
 }
 
 func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
+	r.bodyLock.RLock()
+	defer r.bodyLock.RUnlock()
+
 	for retry := 0; retry < 2; retry++ {
-		if r.i >= r.size {
+		if r.readOffset >= r.size {
 			return 0, io.EOF
 		}
 
-		if r.i >= r.ib {
-			bufStart := int(r.i - r.ib)
-			bufEnd := bufStart + len(p)
-			if bufEnd <= len(r.buf) {
-				copy(p, r.buf[bufStart:bufEnd])
-				r.i += int64(len(p))
-				return len(p), nil
+		if r.readOffset >= r.bufferOffset {
+			bufStart := r.readOffset - r.bufferOffset
+
+			if bufStart <= int64(len(r.buf)) {
+				bufEnd := bufStart + int64(len(p))
+				if bufEnd >= int64(len(r.buf)) {
+					bufEnd = int64(len(r.buf))
+				}
+
+				if bufEnd-bufStart > 0 {
+					copy(p, r.buf[bufStart:bufEnd])
+					r.readOffset += bufEnd - bufStart
+					return int(bufEnd - bufStart), nil
+				}
 			}
 		}
 
 		if r.body == nil {
-			if err = r.retryConnect(); err != nil {
+			if err = func() error {
+				r.bodyLock.RUnlock()
+				defer r.bodyLock.RLock()
+				return r.retryConnect()
+			}(); err != nil {
 				continue
 			}
 		}
@@ -113,7 +128,7 @@ func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
 		n, err = r.body.Read(data)
 		if err != nil { //detect actual eof, not a disconnection
 			if err == io.EOF || err == io.ErrUnexpectedEOF {
-				if r.i+int64(n) != r.size {
+				if r.readOffset+int64(n) != r.size {
 					continue
 				}
 			} else {
@@ -121,7 +136,7 @@ func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
 			}
 		}
 		r.buf = data[:n]
-		r.ib = r.i
+		r.bufferOffset = r.readOffset
 
 		readBytes := len(p)
 		if n < readBytes {
@@ -129,7 +144,7 @@ func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
 		}
 
 		copy(p[:readBytes], data[:readBytes])
-		r.i += int64(readBytes)
+		r.readOffset += int64(readBytes)
 		return readBytes, nil
 	}
 
@@ -137,37 +152,44 @@ func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
 }
 
 func (r *RangeReadSeekCloser) Seek(offset int64, whence int) (int64, error) {
+	r.bodyLock.Lock()
+	defer r.bodyLock.Unlock()
+
+	oldOffset := r.readOffset
+
 	switch whence {
 	case io.SeekStart:
-		r.i = offset
+		r.readOffset = offset
 
 	case io.SeekCurrent:
-		r.i += offset
+		r.readOffset += offset
 
 	case io.SeekEnd:
 		//todo: maybe without -1?
-		r.i = (r.size - 1) - offset
+		r.readOffset = (r.size - 1) - offset
 	default:
 		return 0, fmt.Errorf("unknown whence %d", whence)
 	}
 
-	if r.i >= r.size {
-		return r.i, io.EOF
-	} else if r.i < 0 {
-		return r.i, io.ErrUnexpectedEOF
-	}
-
-	if r.i < r.ib || r.i >= r.ib+int64(len(r.buf)) {
+	if oldOffset != r.readOffset {
 		if r.body != nil {
 			r.body.Close()
 		}
 		r.body = nil
 	}
 
-	return r.i, nil
+	if r.readOffset >= r.size {
+		return r.readOffset, io.EOF
+	} else if r.readOffset < 0 {
+		return r.readOffset, io.ErrUnexpectedEOF
+	}
+
+	return r.readOffset, nil
 }
 
 func (r *RangeReadSeekCloser) Close() error {
+	r.bodyLock.Lock()
+	defer r.bodyLock.Unlock()
 	if r.body != nil {
 		r.closed = true
 		defer func() {