pristineio/wsd

'use strict';
//
// wsd
// Copyright(c) 2011 Einar Otto Stangvik <einaros@gmail.com>
// MIT Licensed
//

try {
  module.exports = require('bufferutil');
} catch (e) {
  module.exports = {
    merge: function(mergedBuffer, buffers) {
      var offset = 0;
      for (var i=0, l=buffers.length; i<l; ++i) {
        var buf = buffers[i];
        buf.copy(mergedBuffer, offset);
        offset += buf.length;
      }
    },
    mask: function(source, mask, output, offset, length) {
      var maskNum = mask.readUInt32LE(0, true);
      var i = 0;
      for(; i<length-3; i+=4) {
        var num = maskNum ^ source.readUInt32LE(i, true);
        if(num < 0) {
          num = 4294967296 + num;
        }
        output.writeUInt32LE(num, offset + i, true);
      }
      switch(length % 4) {
        case 3:
          output[offset + i + 2] = source[i + 2] ^ mask[2];
          break;
        case 2:
          output[offset + i + 1] = source[i + 1] ^ mask[1];
          break;
        case 1:
          output[offset + i] = source[i] ^ mask[0];
      }
    },
    unmask: function(data, mask) {
      var maskNum = mask.readUInt32LE(0, true);
      var length = data.length;
      var i = 0;
      for(; i<length-3; i+=4) {
        var num = maskNum ^ data.readUInt32LE(i, true);
        if(num < 0) {
          num = 4294967296 + num;
        }
        data.writeUInt32LE(num, i, true);
      }
      switch(length % 4) {
        case 3:
          data[i + 2] = data[i + 2] ^ mask[2];
          break;
        case 2:
          data[i + 1] = data[i + 1] ^ mask[1];
          break;
        case 1:
          data[i] = data[i] ^ mask[0];
          break;
      }
    }
  };
}