1 | /* |
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2 | * Copyright (c) 2017-2018 Rafael da Silva Rocha. |
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3 | * |
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4 | * Permission is hereby granted, free of charge, to any person obtaining |
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5 | * a copy of this software and associated documentation files (the |
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6 | * "Software"), to deal in the Software without restriction, including |
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7 | * without limitation the rights to use, copy, modify, merge, publish, |
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8 | * distribute, sublicense, and/or sell copies of the Software, and to |
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9 | * permit persons to whom the Software is furnished to do so, subject to |
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10 | * the following conditions: |
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11 | * |
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12 | * The above copyright notice and this permission notice shall be |
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13 | * included in all copies or substantial portions of the Software. |
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14 | * |
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15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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16 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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17 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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18 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE |
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19 | * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
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20 | * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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21 | * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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22 | * |
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23 | */ |
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24 | |||
25 | /** |
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26 | * @fileoverview Pack and unpack two's complement ints and unsigned ints. |
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27 | * @see https://github.com/rochars/byte-data |
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28 | */ |
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29 | |||
30 | /** |
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31 | * A class to pack and unpack two's complement ints and unsigned ints. |
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32 | */ |
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33 | export default class Integer { |
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34 | |||
35 | constructor() { |
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36 | /** |
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37 | * @type {number} |
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38 | */ |
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39 | this.offset = 0; |
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40 | /** |
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41 | * @type {number} |
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42 | */ |
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43 | this.realOffset_ = 0; |
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44 | /** |
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45 | * @type {number} |
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46 | * @private |
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47 | */ |
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48 | this.bits_ = 0; |
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49 | /** |
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50 | * @type {number} |
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51 | * @private |
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52 | */ |
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53 | this.lastByteMask_ = 0; |
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54 | /** |
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55 | * @type {number} |
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56 | * @private |
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57 | */ |
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58 | this.max_ = 0; |
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59 | /** |
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60 | * @type {number} |
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61 | * @private |
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62 | */ |
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63 | this.min_ = 0; |
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64 | } |
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65 | |||
66 | /** |
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67 | * Set up the object to start serializing/deserializing a data type.. |
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68 | * @param {!Object} theType The type definition. |
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69 | */ |
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70 | setUp(theType) { |
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71 | /** |
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72 | * The max number of bits used by the data. |
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73 | * @type {number} |
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74 | * @private |
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75 | */ |
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76 | this.bits_ = theType.bits; |
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77 | // Set the min and max values according to the number of bits |
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78 | /** @type {number} */ |
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79 | let max = Math.pow(2, this.bits_); |
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80 | if (theType.signed) { |
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81 | this.max_ = max / 2 -1; |
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82 | this.min_ = -max / 2; |
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83 | } else { |
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84 | this.max_ = max - 1; |
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85 | this.min_ = 0; |
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86 | } |
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87 | this.setLastByteMask_(); |
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88 | this.offset = this.bits_ < 8 ? 1 : Math.ceil(this.bits_ / 8); |
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89 | this.realOffset_ = this.bits_ === 64 ? 4 : this.offset; |
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90 | } |
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91 | |||
92 | /** |
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93 | * Read one integer number from a byte buffer. |
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94 | * @param {!Uint8Array} bytes An array of bytes. |
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95 | * @param {number=} i The index to read. |
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96 | * @return {number} |
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97 | */ |
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98 | read(bytes, i=0) { |
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99 | let num = 0; |
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100 | for(let x=0; x<this.realOffset_; x++) { |
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101 | num += bytes[i + x] * Math.pow(256, x); |
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102 | } |
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103 | return this.overflow_(this.sign_(num)); |
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104 | } |
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105 | |||
106 | /** |
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107 | * Write one integer number to a byte buffer. |
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108 | * @param {!Uint8Array} bytes An array of bytes. |
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109 | * @param {number} num The number. |
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110 | * @param {number=} j The index being written in the byte buffer. |
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111 | * @return {number} The next index to write on the byte buffer. |
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112 | * @private |
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113 | */ |
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114 | write(bytes, num, j=0) { |
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115 | j = this.writeFirstByte_(bytes, this.overflow_(num), j); |
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116 | for (let i = 2, len = this.realOffset_; i < len; i++, j++) { |
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117 | bytes[j] = Math.floor(num / Math.pow(2, ((i - 1) * 8))) & 255; |
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118 | } |
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119 | if (this.bits_ > 8) { |
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120 | bytes[j] = Math.floor( |
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121 | num / Math.pow(2, ((this.realOffset_ - 1) * 8))) & this.lastByteMask_; |
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122 | j++; |
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123 | } |
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124 | return j; |
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125 | } |
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126 | |||
127 | /** |
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128 | * Sign a number. |
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129 | * @param {number} num The number. |
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130 | * @return {number} |
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131 | * @private |
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132 | */ |
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133 | sign_(num) { |
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134 | if (num > this.max_) { |
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135 | num -= (this.max_ * 2) + 2; |
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136 | } |
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137 | return num; |
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138 | } |
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139 | |||
140 | /** |
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141 | * Trows error in case of underflow or overflow. |
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142 | * @param {number} num The number. |
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143 | * @return {number} |
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144 | * @throws {Error} on overflow or underflow. |
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145 | * @private |
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146 | */ |
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147 | overflow_(num) { |
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148 | if (num > this.max_) { |
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149 | throw new Error('Overflow.'); |
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150 | } else if (num < this.min_) { |
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151 | throw new Error('Underflow.'); |
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152 | } |
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153 | return num; |
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154 | } |
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155 | |||
156 | /** |
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157 | * Set the mask that should be used when writing the last byte. |
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158 | * @private |
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159 | */ |
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160 | setLastByteMask_() { |
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161 | /** @type {number} */ |
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162 | let r = 8 - ((((this.bits_ - 1) | 7) + 1) - this.bits_); |
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163 | this.lastByteMask_ = Math.pow(2, r > 0 ? r : 8) - 1; |
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164 | } |
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165 | |||
166 | /** |
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167 | * Write the first byte of a integer number. |
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168 | * @param {!Uint8Array} bytes An array of bytes. |
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169 | * @param {number} number The number. |
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170 | * @param {number} j The index being written in the byte buffer. |
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171 | * @return {number} The next index to write on the byte buffer. |
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172 | * @private |
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173 | */ |
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174 | writeFirstByte_(bytes, number, j) { |
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175 | if (this.bits_ < 8) { |
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176 | bytes[j] = number < 0 ? number + Math.pow(2, this.bits_) : number; |
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177 | } else { |
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178 | bytes[j] = number & 255; |
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179 | } |
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180 | return j + 1; |
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181 | } |
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182 | } |
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183 |