refactor: merge readers and writers

modules/zstd/zstd.go

@@ -10,73 +10,49 @@ import (
 	"github.com/klauspost/compress/zstd"
 )
 
-type Writer zstd.Encoder
+type Writer struct {
+	enc *zstd.Encoder
 
-var _ io.WriteCloser = (*Writer)(nil)
-
-func NewWriter(w io.Writer, opts ...WriterOption) (*Writer, error) {
-	zstdW, err := zstd.NewWriter(w, opts...)
-	if err != nil {
-		return nil, err
-	}
-	return (*Writer)(zstdW), nil
-}
-
-func (w *Writer) Write(p []byte) (int, error) {
-	return (*zstd.Encoder)(w).Write(p)
-}
-
-func (w *Writer) Close() error {
-	return (*zstd.Encoder)(w).Close()
+	skw seekable.Writer
+	buf []byte
+	n   int
 }
 
-type Reader zstd.Decoder
-
-var _ io.ReadCloser = (*Reader)(nil)
+var _ io.WriteCloser = (*Writer)(nil)
 
-func NewReader(r io.Reader, opts ...ReaderOption) (*Reader, error) {
-	zstdR, err := zstd.NewReader(r, opts...)
+func NewWriter(w io.Writer, opts ...WriterOption) (*Writer, error) {
+	enc, err := zstd.NewWriter(w, opts...)
 	if err != nil {
 		return nil, err
 	}
-	return (*Reader)(zstdR), nil
-}
-
-func (r *Reader) Read(p []byte) (int, error) {
-	return (*zstd.Decoder)(r).Read(p)
-}
-
-func (r *Reader) Close() error {
-	(*zstd.Decoder)(r).Close() // no error returned
-	return nil
-}
-
-type SeekableWriter struct {
-	buf []byte
-	n   int
-	w   seekable.Writer
+	return &Writer{
+		enc: enc,
+	}, nil
 }
 
-var _ io.WriteCloser = (*SeekableWriter)(nil)
-
-func NewSeekableWriter(w io.Writer, blockSize int, opts ...WriterOption) (*SeekableWriter, error) {
-	zstdW, err := zstd.NewWriter(nil, opts...)
+func NewSeekableWriter(w io.Writer, blockSize int, opts ...WriterOption) (*Writer, error) {
+	enc, err := zstd.NewWriter(nil, opts...)
 	if err != nil {
 		return nil, err
 	}
 
-	seekableW, err := seekable.NewWriter(w, zstdW)
+	skw, err := seekable.NewWriter(w, enc)
 	if err != nil {
 		return nil, err
 	}
 
-	return &SeekableWriter{
+	return &Writer{
+		enc: enc,
+		skw: skw,
 		buf: make([]byte, blockSize),
-		w:   seekableW,
 	}, nil
 }
 
-func (w *SeekableWriter) Write(p []byte) (int, error) {
+func (w *Writer) Write(p []byte) (int, error) {
+	if w.skw != nil {
+		return w.enc.Write(p)
+	}
+
 	written := 0
 	for len(p) > 0 {
 		n := copy(w.buf[w.n:], p)
@@ -85,7 +61,7 @@ func (w *SeekableWriter) Write(p []byte) (int, error) {
 		p = p[n:]
 
 		if w.n == len(w.buf) {
-			if _, err := w.w.Write(w.buf); err != nil {
+			if _, err := w.skw.Write(w.buf); err != nil {
 				return written, err
 			}
 			w.n = 0
@@ -94,13 +70,48 @@ func (w *SeekableWriter) Write(p []byte) (int, error) {
 	return written, nil
 }
 
-func (w *SeekableWriter) Close() error {
-	if w.n > 0 {
-		if _, err := w.w.Write(w.buf[:w.n]); err != nil {
+func (w *Writer) Close() error {
+	if w.skw != nil {
+		if w.n > 0 {
+			if _, err := w.skw.Write(w.buf[:w.n]); err != nil {
+				return err
+			}
+		}
+		if err := w.skw.Close(); err != nil {
 			return err
 		}
 	}
-	return w.w.Close()
+	return w.enc.Close()
+}
+
+type Reader struct {
+	dec *zstd.Decoder
+	skr seekable.Reader
+}
+
+var _ io.ReadCloser = (*Reader)(nil)
+
+func NewReader(r io.Reader, opts ...ReaderOption) (*Reader, error) {
+	dec, err := zstd.NewReader(r, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return &Reader{
+		dec: dec,
+	}, nil
+}
+
+func (r *Reader) Read(p []byte) (int, error) {
+	return r.dec.Read(p)
+}
+
+func (r *Reader) Close() error {
+	r.dec.Close() // no error returned
+	return nil
+}
+
+func (r *Reader) SeekReader() (seekable.Reader, error) {
+	return r.skr
 }
 
 type SeekableReader seekable.Reader