Fix zstd potential memory leak (#584)

Author: aryehlev

ocf/codec.go

@@ -162,3 +162,14 @@ func (zstdCodec *ZStandardCodec) Encode(b []byte) []byte {
 	defer zstdCodec.encoder.Reset(nil)
 	return zstdCodec.encoder.EncodeAll(b, nil)
 }
+
+// Close closes the zstandard encoder and decoder, releasing resources.
+func (zstdCodec *ZStandardCodec) Close() error {
+	if zstdCodec.decoder != nil {
+		zstdCodec.decoder.Close()
+	}
+	if zstdCodec.encoder != nil {
+		return zstdCodec.encoder.Close()
+	}
+	return nil
+}

ocf/ocf.go

@@ -176,6 +176,14 @@ func (d *Decoder) Error() error {
 	return d.reader.Error
 }
 
+// Close releases codec resources.
+func (d *Decoder) Close() error {
+	if c, ok := d.codec.(io.Closer); ok {
+		return c.Close()
+	}
+	return nil
+}
+
 func (d *Decoder) readBlock() int64 {
 	_ = d.reader.Peek()
 	if errors.Is(d.reader.Error, io.EOF) {
@@ -496,9 +504,15 @@ func (e *Encoder) Flush() error {
 	return e.writer.Error
 }
 
-// Close closes the encoder, flushing the writer.
+// Close closes the encoder, flushing the writer and releasing codec resources.
 func (e *Encoder) Close() error {
-	return e.Flush()
+	err := e.Flush()
+	if c, ok := e.codec.(io.Closer); ok {
+		if cerr := c.Close(); cerr != nil && err == nil {
+			err = cerr
+		}
+	}
+	return err
 }
 
 func (e *Encoder) writerBlock() error {