Merge pull request #1490 from 0chain/hotfix/encrypt-buf

fix buf size for write

wasmsdk/jsbridge/file_writer.go

@@ -17,14 +17,21 @@ type FileWriter struct {
 	bufLen         int
 	buf            []byte
 	bufWriteOffset int
+	writeError     bool
 }
 
-const writeBufferSize = 4 * 1024 * 1024 //4MB
+const writeBlocks = 60
 
 // len(p) will always be <= 64KB
 func (w *FileWriter) Write(p []byte) (int, error) {
+	//init buffer if not initialized
+	if len(w.buf) == 0 {
+		w.buf = make([]byte, len(p)*writeBlocks)
+	}
+
 	//copy bytes to buf
 	if w.bufWriteOffset+len(p) > len(w.buf) {
+		w.writeError = true
 		return 0, io.ErrShortWrite
 	}
 	n := copy(w.buf[w.bufWriteOffset:], p)
@@ -38,6 +45,7 @@ func (w *FileWriter) Write(p []byte) (int, error) {
 		js.CopyBytesToJS(w.uint8Array, w.buf)
 		_, err := Await(w.writableStream.Call("write", w.uint8Array))
 		if len(err) > 0 && !err[0].IsNull() {
+			w.writeError = true
 			return 0, errors.New("file_writer: " + err[0].String())
 		}
 		//reset buffer
@@ -63,7 +71,7 @@ func (w *FileWriter) Write(p []byte) (int, error) {
 
 func (w *FileWriter) Close() error {
 
-	if w.bufWriteOffset > 0 {
+	if w.bufWriteOffset > 0 && !w.writeError {
 		w.buf = w.buf[:w.bufWriteOffset]
 		uint8Array := js.Global().Get("Uint8Array").New(len(w.buf))
 		js.CopyBytesToJS(uint8Array, w.buf)
@@ -120,6 +128,5 @@ func NewFileWriter(filename string) (*FileWriter, error) {
 	return &FileWriter{
 		writableStream: writableStream[0],
 		fileHandle:     fileHandle[0],
-		buf:            make([]byte, writeBufferSize),
 	}, nil
 }