UTF8 decode CombinedBuffer in web browser env.

- Refactor, create helper function for stream decoding.

Author: oskarhane

lib/internal/utf8.js

@@ -43,22 +43,12 @@ try {
         return buffer._buffer.toString( 'utf8', start, end );
       } 
       else if( buffer instanceof buf.CombinedBuffer ) {
-        let remainingBytesToRead = length;
-        // Reduce CombinedBuffers to a decoded string
-        let out = buffer._buffers.reduce(function(last, partBuffer){
-          if(remainingBytesToRead <= 0) {
-            return last;
-          }
-          if(partBuffer.length > remainingBytesToRead) { // When we don't want the whole buffer
-            let lastSlice = partBuffer.readSlice(remainingBytesToRead);
-            partBuffer._updatePos(remainingBytesToRead);
-            remainingBytesToRead = 0;
-            return last + decoder.write(lastSlice._buffer);
-          }
-          remainingBytesToRead -= partBuffer.length;
-          return last + decoder.write(partBuffer._buffer);
-        }, '');
-        out += decoder.end();
+        let out = streamDecodeCombinedBuffer(buffer._buffers, length,
+          (partBuffer) => {
+            return decoder.write(partBuffer._buffer);
+          },
+          () => { return decoder.end(); }
+        );
         return out;
       } 
       else {
@@ -81,11 +71,40 @@ try {
     "decode" : function( buffer, length ) {
       if( buffer instanceof buf.HeapBuffer ) {
         return decoder.decode( buffer.readView( length ) );
-      } else {
+      }
+      else if( buffer instanceof buf.CombinedBuffer ) {
+        let out = streamDecodeCombinedBuffer(buffer._buffers, length,
+          (partBuffer) => {
+            return decoder.decode(partBuffer.readView(partBuffer.length), {stream:true});
+          },
+          () => { return decoder.decode(); }
+        );
+        return out;
+      } 
+      else {
         throw new Error( "Don't know how to decode strings from `" + buffer + "`.");
       }
     }
   }
 }
 
+let streamDecodeCombinedBuffer = (combinedBuffers, length, decodeFn, endFn) => {
+  let remainingBytesToRead = length;
+  let out = combinedBuffers.reduce(function(last, partBuffer){
+    if(remainingBytesToRead <= 0) {
+      return last;
+    }
+    if(partBuffer.length > remainingBytesToRead) { // When we don't want the whole buffer
+      let lastSlice = partBuffer.readSlice(remainingBytesToRead);
+      partBuffer._updatePos(remainingBytesToRead);
+      remainingBytesToRead = 0;
+      return last + decodeFn(lastSlice);
+    }
+    remainingBytesToRead -= partBuffer.length;
+    let tmp = decodeFn(partBuffer);
+    return last + tmp;
+  }, '');
+  return out + endFn();
+}
+
 export default platformObj;