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/* |
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* Copyright (c) 2018-2019 Rafael da Silva Rocha. |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining |
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* a copy of this software and associated documentation files (the |
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* "Software"), to deal in the Software without restriction, including |
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* without limitation the rights to use, copy, modify, merge, publish, |
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* distribute, sublicense, and/or sell copies of the Software, and to |
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* permit persons to whom the Software is furnished to do so, subject to |
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* the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be |
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* included in all copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE |
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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* |
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*/ |
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/** |
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* @fileoverview Parse two's complement ints to and from byte buffers. |
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* @see https://github.com/rochars/twos-complement-buffer |
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*/ |
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/** @module twos-complement-buffer */ |
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import { UintBuffer } from 'uint-buffer'; |
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/** |
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* A class to parse two's complement signed integers |
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* to and from byte buffers. |
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* @extends UintBuffer |
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*/ |
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export class TwosComplementBuffer extends UintBuffer { |
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/** |
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* @param {number} bits The number of bits used by the integer. |
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*/ |
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constructor(bits) { |
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super(bits); |
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/** |
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* @type {number} |
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* @protected |
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*/ |
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this.max = Math.pow(2, this.bits) / 2 - 1; |
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/** |
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* @type {number} |
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* @protected |
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*/ |
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this.min = -this.max - 1; |
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} |
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/** |
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* Write one two's complement signed integer to a byte buffer. |
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* @param {!Uint8Array|!Array<number>} buffer An array of bytes. |
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* @param {number} num The number. |
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* @param {number=} index The index being written in the byte buffer. |
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* @return {number} The next index to write on the byte buffer. |
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* @throws {TypeError} If num is NaN. |
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* @throws {RangeError} On overflow. |
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*/ |
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pack(buffer, num, index=0) { |
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return super.pack(buffer, num, index); |
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} |
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/** |
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* Read one two's complement signed integer from a byte buffer. |
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* @param {!Uint8Array|!Array<number>} buffer An array of bytes. |
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* @param {number=} index The index to read. |
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* @return {number} |
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* @throws {RangeError} On overflow. |
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*/ |
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unpack(buffer, index=0) { |
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/** @type {number} */ |
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let num = super.unpackUnsafe(buffer, index); |
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num = this.sign_(num); |
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this.overflow(num); |
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return num; |
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} |
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/** |
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* Sign a number. |
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* @param {number} num The number. |
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* @return {number} |
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* @private |
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*/ |
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sign_(num) { |
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if (num > this.max) { |
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num -= (this.max * 2) + 2; |
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} |
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return num; |
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} |
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} |
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rochars /
twos-complement-buffer
