Pinsave/counterstrike

1/* -*- Mode: js; js-indent-level: 2; -*- */2/*3 * Copyright 2011 Mozilla Foundation and contributors4 * Licensed under the New BSD license. See LICENSE or:5 * http://opensource.org/licenses/BSD-3-Clause6 *7 * Based on the Base 64 VLQ implementation in Closure Compiler:8 * https://code.google.com/p/closure-compiler/source/browse/trunk/src/com/google/debugging/sourcemap/Base64VLQ.java9 *10 * Copyright 2011 The Closure Compiler Authors. All rights reserved.11 * Redistribution and use in source and binary forms, with or without12 * modification, are permitted provided that the following conditions are13 * met:14 *15 *  * Redistributions of source code must retain the above copyright16 *    notice, this list of conditions and the following disclaimer.17 *  * Redistributions in binary form must reproduce the above18 *    copyright notice, this list of conditions and the following19 *    disclaimer in the documentation and/or other materials provided20 *    with the distribution.21 *  * Neither the name of Google Inc. nor the names of its22 *    contributors may be used to endorse or promote products derived23 *    from this software without specific prior written permission.24 *25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.36 */37 38var base64 = require('./base64');39 40// A single base 64 digit can contain 6 bits of data. For the base 64 variable41// length quantities we use in the source map spec, the first bit is the sign,42// the next four bits are the actual value, and the 6th bit is the43// continuation bit. The continuation bit tells us whether there are more44// digits in this value following this digit.45//46//   Continuation47//   |    Sign48//   |    |49//   V    V50//   10101151 52var VLQ_BASE_SHIFT = 5;53 54// binary: 10000055var VLQ_BASE = 1 << VLQ_BASE_SHIFT;56 57// binary: 01111158var VLQ_BASE_MASK = VLQ_BASE - 1;59 60// binary: 10000061var VLQ_CONTINUATION_BIT = VLQ_BASE;62 63/**64 * Converts from a two-complement value to a value where the sign bit is65 * placed in the least significant bit.  For example, as decimals:66 *   1 becomes 2 (10 binary), -1 becomes 3 (11 binary)67 *   2 becomes 4 (100 binary), -2 becomes 5 (101 binary)68 */69function toVLQSigned(aValue) {70  return aValue < 071    ? ((-aValue) << 1) + 172    : (aValue << 1) + 0;73}74 75/**76 * Converts to a two-complement value from a value where the sign bit is77 * placed in the least significant bit.  For example, as decimals:78 *   2 (10 binary) becomes 1, 3 (11 binary) becomes -179 *   4 (100 binary) becomes 2, 5 (101 binary) becomes -280 */81function fromVLQSigned(aValue) {82  var isNegative = (aValue & 1) === 1;83  var shifted = aValue >> 1;84  return isNegative85    ? -shifted86    : shifted;87}88 89/**90 * Returns the base 64 VLQ encoded value.91 */92exports.encode = function base64VLQ_encode(aValue) {93  var encoded = "";94  var digit;95 96  var vlq = toVLQSigned(aValue);97 98  do {99    digit = vlq & VLQ_BASE_MASK;100    vlq >>>= VLQ_BASE_SHIFT;101    if (vlq > 0) {102      // There are still more digits in this value, so we must make sure the103      // continuation bit is marked.104      digit |= VLQ_CONTINUATION_BIT;105    }106    encoded += base64.encode(digit);107  } while (vlq > 0);108 109  return encoded;110};111 112/**113 * Decodes the next base 64 VLQ value from the given string and returns the114 * value and the rest of the string via the out parameter.115 */116exports.decode = function base64VLQ_decode(aStr, aIndex, aOutParam) {117  var strLen = aStr.length;118  var result = 0;119  var shift = 0;120  var continuation, digit;121 122  do {123    if (aIndex >= strLen) {124      throw new Error("Expected more digits in base 64 VLQ value.");125    }126 127    digit = base64.decode(aStr.charCodeAt(aIndex++));128    if (digit === -1) {129      throw new Error("Invalid base64 digit: " + aStr.charAt(aIndex - 1));130    }131 132    continuation = !!(digit & VLQ_CONTINUATION_BIT);133    digit &= VLQ_BASE_MASK;134    result = result + (digit << shift);135    shift += VLQ_BASE_SHIFT;136  } while (continuation);137 138  aOutParam.value = fromVLQSigned(result);139  aOutParam.rest = aIndex;140};141