Reuse buffer after read (#15)

* Reuse buffer after read

Instead of waiting for the next Read, send back the buffer after read if no longer used.

* Test with race
* Add defaults as constants.

Author: klauspost

.github/workflows/go.yml

@@ -27,8 +27,8 @@ jobs:
     - name: Test
       run: go test ./...
 
-    - name: Test Noasm
-      run: go test -tags=noasm ./...
+    - name: Test Race
+      run: go test -race -cpu=1,4,8 ./...
 
   build-special:
     env:
@@ -47,4 +47,4 @@ jobs:
       run: diff <(gofmt -d .) <(printf "")
 
     - name: Test 386
-      run: GOOS=linux GOARCH=386 go test -short ./...
+      run: GOOS=linux GOARCH=386 go test ./...

reader.go

@@ -19,6 +19,14 @@ import (
 	"io"
 )
 
+const (
+	// DefaultBuffers is the default number of buffers used.
+	DefaultBuffers = 4
+
+	// DefaultBufferSize is the default buffer size, 1 MB.
+	DefaultBufferSize = 1 << 20
+)
+
 type seekable struct {
 	*reader
 }
@@ -57,7 +65,7 @@ func NewReader(rd io.Reader) io.ReadCloser {
 		return nil
 	}
 
-	ret, err := NewReaderSize(rd, 4, 1<<20)
+	ret, err := NewReaderSize(rd, DefaultBuffers, DefaultBufferSize)
 
 	// Should not be possible to trigger from other packages.
 	if err != nil {
@@ -82,7 +90,7 @@ func NewReadCloser(rd io.ReadCloser) io.ReadCloser {
 		return nil
 	}
 
-	ret, err := NewReadCloserSize(rd, 4, 1<<20)
+	ret, err := NewReadCloserSize(rd, DefaultBuffers, DefaultBufferSize)
 
 	// Should not be possible to trigger from other packages.
 	if err != nil {
@@ -145,6 +153,7 @@ func NewReaderSize(rd io.Reader, buffers, size int) (res io.ReadCloser, err erro
 
 // NewReaderBuffer returns a reader with a custom number of buffers and size.
 // All buffers must be the same size.
+// Buffers can be reused after Close has been called.
 func NewReaderBuffer(rd io.Reader, buffers [][]byte) (res io.ReadCloser, err error) {
 	if len(buffers) == 0 {
 		return nil, fmt.Errorf("number of buffers too small")
@@ -200,6 +209,7 @@ func NewReadCloserSize(rc io.ReadCloser, buffers, size int) (res io.ReadCloser,
 
 // NewReadCloserBuffer returns a reader with a custom number of buffers and size.
 // All buffers must be the same size.
+// Buffers can be reused after Close has been called.
 func NewReadCloserBuffer(rc io.ReadCloser, buffers [][]byte) (res io.ReadCloser, err error) {
 	if len(buffers) == 0 {
 		return nil, fmt.Errorf("number of buffers too small")
@@ -258,6 +268,7 @@ func NewReadSeekCloserSize(rd ReadSeekCloser, buffers, size int) (res ReadSeekCl
 
 // NewReadSeekCloserBuffer returns a reader with a custom number of buffers and size.
 // All buffers must be the same size.
+// Buffers can be reused after Close has been called.
 func NewReadSeekCloserBuffer(rd ReadSeekCloser, buffers [][]byte) (res ReadSeekCloser, err error) {
 	reader, err := NewReadCloserBuffer(rd, buffers)
 	if err != nil {
@@ -293,7 +304,7 @@ func (a *reader) initBuffers(rd io.Reader, buffers [][]byte, size int) {
 
 	// Create buffers
 	for _, buf := range buffers {
-		a.reuse <- newBufferBuf(buf)
+		a.reuse <- newBuffer(buf)
 	}
 
 	// Start async reader
@@ -351,9 +362,14 @@ func (a *reader) Read(p []byte) (n int, err error) {
 	n = copy(p, a.cur.buffer())
 	a.cur.inc(n)
 
-	// If at end of buffer, return any error, if present
 	if a.cur.isEmpty() {
-		a.err = a.cur.err
+		// Return current, so a fetch can start.
+		if a.cur != nil {
+			// If at end of buffer, return any error, if present
+			a.err = a.cur.err
+			a.reuse <- a.cur
+			a.cur = nil
+		}
 		return n, a.err
 	}
 	return n, nil
@@ -446,11 +462,7 @@ type buffer struct {
 	size   int
 }
 
-func newBuffer(size int) *buffer {
-	return &buffer{buf: make([]byte, size), err: nil, size: size}
-}
-
-func newBufferBuf(buf []byte) *buffer {
+func newBuffer(buf []byte) *buffer {
 	return &buffer{buf: buf, err: nil, size: len(buf)}
 }