[6a3a178] | 1 | /* -*- Mode: js; js-indent-level: 2; -*- */
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| 2 | /*
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| 3 | * Copyright 2011 Mozilla Foundation and contributors
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| 4 | * Licensed under the New BSD license. See LICENSE or:
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| 5 | * http://opensource.org/licenses/BSD-3-Clause
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| 6 | *
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| 7 | * Based on the Base 64 VLQ implementation in Closure Compiler:
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| 8 | * https://code.google.com/p/closure-compiler/source/browse/trunk/src/com/google/debugging/sourcemap/Base64VLQ.java
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| 9 | *
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| 10 | * Copyright 2011 The Closure Compiler Authors. All rights reserved.
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| 11 | * Redistribution and use in source and binary forms, with or without
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| 12 | * modification, are permitted provided that the following conditions are
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| 13 | * met:
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| 14 | *
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| 15 | * * Redistributions of source code must retain the above copyright
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| 16 | * notice, this list of conditions and the following disclaimer.
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| 17 | * * Redistributions in binary form must reproduce the above
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| 18 | * copyright notice, this list of conditions and the following
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| 19 | * disclaimer in the documentation and/or other materials provided
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| 20 | * with the distribution.
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| 21 | * * Neither the name of Google Inc. nor the names of its
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| 22 | * contributors may be used to endorse or promote products derived
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| 23 | * from this software without specific prior written permission.
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| 24 | *
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| 25 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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| 26 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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| 27 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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| 28 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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| 29 | * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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| 30 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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| 31 | * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 32 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 33 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 34 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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| 35 | * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 36 | */
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| 37 |
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| 38 | /*eslint no-bitwise:0,quotes:0,global-strict:0*/
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| 39 |
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| 40 | var charToIntMap = {};
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| 41 | var intToCharMap = {};
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| 42 |
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| 43 | 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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| 44 | .split('')
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| 45 | .forEach(function (ch, index) {
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| 46 | charToIntMap[ch] = index;
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| 47 | intToCharMap[index] = ch;
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| 48 | });
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| 49 |
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| 50 | var base64 = {};
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| 51 | /**
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| 52 | * Encode an integer in the range of 0 to 63 to a single base 64 digit.
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| 53 | */
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| 54 | base64.encode = function base64_encode(aNumber) {
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| 55 | if (aNumber in intToCharMap) {
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| 56 | return intToCharMap[aNumber];
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| 57 | }
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| 58 | throw new TypeError("Must be between 0 and 63: " + aNumber);
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| 59 | };
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| 60 |
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| 61 | /**
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| 62 | * Decode a single base 64 digit to an integer.
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| 63 | */
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| 64 | base64.decode = function base64_decode(aChar) {
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| 65 | if (aChar in charToIntMap) {
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| 66 | return charToIntMap[aChar];
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| 67 | }
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| 68 | throw new TypeError("Not a valid base 64 digit: " + aChar);
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| 69 | };
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| 70 |
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| 71 |
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| 72 |
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| 73 | // A single base 64 digit can contain 6 bits of data. For the base 64 variable
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| 74 | // length quantities we use in the source map spec, the first bit is the sign,
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| 75 | // the next four bits are the actual value, and the 6th bit is the
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| 76 | // continuation bit. The continuation bit tells us whether there are more
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| 77 | // digits in this value following this digit.
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| 78 | //
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| 79 | // Continuation
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| 80 | // | Sign
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| 81 | // | |
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| 82 | // V V
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| 83 | // 101011
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| 84 |
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| 85 | var VLQ_BASE_SHIFT = 5;
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| 86 |
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| 87 | // binary: 100000
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| 88 | var VLQ_BASE = 1 << VLQ_BASE_SHIFT;
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| 89 |
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| 90 | // binary: 011111
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| 91 | var VLQ_BASE_MASK = VLQ_BASE - 1;
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| 92 |
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| 93 | // binary: 100000
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| 94 | var VLQ_CONTINUATION_BIT = VLQ_BASE;
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| 95 |
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| 96 | /**
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| 97 | * Converts from a two-complement value to a value where the sign bit is
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| 98 | * placed in the least significant bit. For example, as decimals:
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| 99 | * 1 becomes 2 (10 binary), -1 becomes 3 (11 binary)
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| 100 | * 2 becomes 4 (100 binary), -2 becomes 5 (101 binary)
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| 101 | */
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| 102 | function toVLQSigned(aValue) {
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| 103 | return aValue < 0
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| 104 | ? ((-aValue) << 1) + 1
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| 105 | : (aValue << 1) + 0;
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| 106 | }
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| 107 |
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| 108 | /**
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| 109 | * Converts to a two-complement value from a value where the sign bit is
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| 110 | * placed in the least significant bit. For example, as decimals:
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| 111 | * 2 (10 binary) becomes 1, 3 (11 binary) becomes -1
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| 112 | * 4 (100 binary) becomes 2, 5 (101 binary) becomes -2
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| 113 | */
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| 114 | function fromVLQSigned(aValue) {
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| 115 | var isNegative = (aValue & 1) === 1;
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| 116 | var shifted = aValue >> 1;
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| 117 | return isNegative
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| 118 | ? -shifted
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| 119 | : shifted;
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| 120 | }
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| 121 |
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| 122 | /**
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| 123 | * Returns the base 64 VLQ encoded value.
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| 124 | */
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| 125 | exports.encode = function base64VLQ_encode(aValue) {
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| 126 | var encoded = "";
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| 127 | var digit;
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| 128 |
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| 129 | var vlq = toVLQSigned(aValue);
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| 130 |
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| 131 | do {
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| 132 | digit = vlq & VLQ_BASE_MASK;
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| 133 | vlq >>>= VLQ_BASE_SHIFT;
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| 134 | if (vlq > 0) {
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| 135 | // There are still more digits in this value, so we must make sure the
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| 136 | // continuation bit is marked.
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| 137 | digit |= VLQ_CONTINUATION_BIT;
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| 138 | }
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| 139 | encoded += base64.encode(digit);
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| 140 | } while (vlq > 0);
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| 141 |
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| 142 | return encoded;
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| 143 | };
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| 144 |
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| 145 | /**
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| 146 | * Decodes the next base 64 VLQ value from the given string and returns the
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| 147 | * value and the rest of the string via the out parameter.
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| 148 | */
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| 149 | exports.decode = function base64VLQ_decode(aStr, aOutParam) {
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| 150 | var i = 0;
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| 151 | var strLen = aStr.length;
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| 152 | var result = 0;
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| 153 | var shift = 0;
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| 154 | var continuation, digit;
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| 155 |
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| 156 | do {
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| 157 | if (i >= strLen) {
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| 158 | throw new Error("Expected more digits in base 64 VLQ value.");
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| 159 | }
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| 160 | digit = base64.decode(aStr.charAt(i++));
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| 161 | continuation = !!(digit & VLQ_CONTINUATION_BIT);
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| 162 | digit &= VLQ_BASE_MASK;
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| 163 | result = result + (digit << shift);
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| 164 | shift += VLQ_BASE_SHIFT;
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| 165 | } while (continuation);
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| 166 |
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| 167 | aOutParam.value = fromVLQSigned(result);
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| 168 | aOutParam.rest = aStr.slice(i);
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| 169 | };
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