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/* |
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* Copyright (c) 2017-2018 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 Encode and decode int numbers to and from byte buffers. |
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* @see https://github.com/rochars/byte-data |
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* @see https://github.com/rochars/wavefile |
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*/ |
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/** |
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* A class to write and read integer numbers to and from byte buffers. |
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*/ |
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export class IntParser { |
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/** |
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* @param {number} bits The number of bits used by the integer. |
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* @param {boolean} [signed=false] True for signed, false otherwise. |
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*/ |
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constructor(bits, signed=false) { |
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/** |
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* The number of bits used by one number. |
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* @type {number} |
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*/ |
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this.bits = bits; |
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/** |
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* The number of bytes used by one number. |
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* @type {number} |
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*/ |
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this.offset = Math.ceil(bits / 8); |
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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, bits) - 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 = 0; |
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/** |
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* @type {Function} |
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*/ |
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this.unpack = this.unpack_; |
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if (signed) { |
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this.max = Math.pow(2, bits) / 2 - 1; |
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this.min = -this.max - 1; |
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this.unpack = this.unpackSigned_; |
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} |
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} |
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/** |
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* Write one unsigned 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. Overflows are truncated. |
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* @param {number} [index=0] 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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*/ |
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pack(buffer, num, index=0) { |
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num = this.clamp_(Math.round(num)); |
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for (let i = 0, len = this.offset; i < len; i++) { |
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buffer[index] = Math.floor(num / Math.pow(2, i * 8)) & 255; |
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index++; |
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} |
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return index; |
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} |
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/** |
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* Read one unsigned integer from a byte buffer. |
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* Does not check for overflows. |
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* @param {!(Uint8Array|Array<number>)} buffer An array of bytes. |
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* @param {number} [index=0] The index to read. |
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* @return {number} |
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* @private |
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*/ |
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unpack_(buffer, index=0) { |
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/** @type {number} */ |
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let num = 0; |
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for(let x = 0; x < this.offset; x++) { |
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num += buffer[index + x] * Math.pow(256, x); |
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} |
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return num; |
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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=0] The index to read. |
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* @return {number} |
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* @private |
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*/ |
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unpackSigned_(buffer, index=0) { |
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return this.sign_(this.unpack_(buffer, index)); |
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} |
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/** |
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* Clamp values on overflow. |
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* @param {number} num The number. |
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* @private |
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*/ |
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clamp_(num) { |
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if (num > this.max) { |
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return this.max; |
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} else if (num < this.min) { |
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return this.min; |
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} |
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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 /
wavefile
