foam-framework/core/writer.js

MVC metaprogramming framework

/**
 * @license
 * Copyright 2012 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

var ProtoWriter = {
   create: function() {
      return {
         __proto__: this,
         value_: []
      };
   },

   get value() { return new Uint8Array(this.value_); },

   varint: function(i) {
      while(i > 0x7f) {
         this.value_.push((i & 0x7f) | 0x80);
         i = Math.floor(i / Math.pow(2, 7));
      }
      this.value_.push(i);
   },

   bytes: function(b) {
      this.value_ = this.value_.concat(b);
   },

   varintstring: function(str) {
     var bytes = [];
     for ( var i = str.length - 2; i > -2; i -= 2 ) {
       var sub = i < 0 ?
         str.substr(0, 1) :
         str.substr(i, 2);

       bytes.push(parseInt(sub, 16));
     }

     var buf = 0;
     for ( var i = 0; i < bytes.length - 1; i++ ) {
       buf >>>= 7;
       buf |= bytes[i] << (i)
       this.value_.push((buf & 0x7f) | 0x80);
     }
     buf >>>= 7;
     buf |= bytes[i] << i;
     this.varint(buf);
   },

   bytestring: function(str) {
      var bytes = [];
      for (var i = 0; i < str.length; i += 2) {
         bytes.push(parseInt(str.substr(i, 2), 16));
      }
      this.bytes(bytes);
   },

   // This is suboptimal, we need a way to insert the length
   // after serializing the message.
   message: function(m) {
      var temp = ProtoWriter.create();
      var data = m.outProtobuf(temp);
      temp = temp.value_;
      this.varint(temp.length);
      this.bytes(temp);
   }
};