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/** |
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* bit-parser: Functions to read and write bytes. |
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* Copyright (c) 2017 Rafael da Silva Rocha. |
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* https://github.com/rochars/byte-data |
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* Floats based on int-bits: https://github.com/Jam3/int-bits |
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* Future: fix https://github.com/majimboo/c-struct 40 and 48-bit |
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*/ |
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/** @private */ |
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let f32 = new Float32Array(1); |
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/** @private */ |
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let i32 = new Int32Array(f32.buffer); |
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/** @private */ |
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let f64 = new Float64Array(1); |
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/** @private */ |
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let ui32 = new Uint32Array(f64.buffer); |
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/** |
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* Functions to read data from bytes. |
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* @enum {Function} |
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*/ |
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const BitReader = { |
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/** |
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* Read 1 8-bit int from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read8Bit": function (bytes, i) { |
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return bytes[i]; |
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}, |
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/** |
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* Read 1 16-bit int from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read16Bit": function (bytes, i) { |
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return bytes[1 + i] << 8 | bytes[i]; |
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}, |
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/** |
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* Read 1 16-bit float from from bytes. |
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* Thanks https://stackoverflow.com/a/8796597 |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read16BitFloat": function (bytes, i) { |
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let binary = parseInt(getBinary([bytes[i], bytes[i+1]]), 2); |
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let exponent = (binary & 0x7C00) >> 10; |
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let fraction = binary & 0x03FF; |
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let floatValue; |
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if (exponent) { |
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floatValue = Math.pow(2, exponent - 15) * (1 + fraction / 0x400); |
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} else { |
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floatValue = 6.103515625e-5 * (fraction / 0x400); |
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} |
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return floatValue * (binary >> 15 ? -1 : 1); |
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}, |
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/** |
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* Read 1 24-bit int from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read24Bit": function (bytes, i) { |
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return bytes[2 + i] << 16 | BitReader["read16Bit"](bytes, i); |
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}, |
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/** |
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* Read 1 32-bit int from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read32Bit": function (bytes, i) { |
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return (bytes[3 + i] << 24 | |
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BitReader["read24Bit"](bytes, i)) >>> 0; |
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}, |
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/** |
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* Read 1 32-bit float from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read32BitFloat": function (bytes, i) { |
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i32[0] = BitReader["read32Bit"](bytes, i); |
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return f32[0]; |
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}, |
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/** |
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* Read 1 40-bit int from from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read40Bit": function (bytes, i) { |
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return readBytesAsBits(bytes, i, 5); |
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}, |
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/** |
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* Read 1 48-bit int from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read48Bit": function (bytes, i) { |
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return readBytesAsBits(bytes, i, 6); |
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}, |
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/** |
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* Read 1 53-bit int from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read53Bit": function (bytes, i) { |
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return readBytesAsBits(bytes, i, 7); |
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}, |
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/** |
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* Read 1 64-bit double from bytes. |
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* Thanks https://gist.github.com/kg/2192799 |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @return {number} |
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*/ |
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"read64BitFloat": function (bytes, i) { |
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ui32[0] = BitReader["read32Bit"](bytes, i); |
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ui32[1] = BitReader["read32Bit"](bytes, i + 4); |
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return f64[0]; |
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}, |
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/** |
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* Read 1 char from bytes. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} i The index to read. |
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* @param {Object} type The index to read. |
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* @return {string} |
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*/ |
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"readChar": function (bytes, i, type) { |
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let chrs = ""; |
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let j = 0; |
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let len = type.bits / 8; |
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while(j < len) { |
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chrs += String.fromCharCode(bytes[i+j]); |
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j++; |
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} |
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return chrs; |
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} |
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}; |
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/** |
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* Functions to write data to bytes. |
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* @enum {Function} |
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*/ |
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let BitWriter = { |
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/** |
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* Write one 64-bit float as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write64BitFloat": function(bytes, number, j) { |
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f64[0] = number; |
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j = BitWriter["write32Bit"](bytes, ui32[0], j); |
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return BitWriter["write32Bit"](bytes, ui32[1], j); |
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}, |
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/** |
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* Write one 53-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write53Bit": function (bytes, number, j) { |
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j = BitWriter["write48Bit"](bytes, number, j); |
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bytes[j++] = Math.floor(number / Math.pow(2, 48)) & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 48-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write48Bit": function (bytes, number, j) { |
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j = BitWriter["write40Bit"](bytes, number, j); |
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bytes[j++] = Math.floor(number / Math.pow(2, 40)) & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 40-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write40Bit": function (bytes, number, j) { |
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j = BitWriter["write32Bit"](bytes, number, j); |
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bytes[j++] = Math.floor(number / Math.pow(2, 32)) & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 32-bit float as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write32BitFloat": function (bytes, number, j) { |
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f32[0] = number; |
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j = BitWriter["write32Bit"](bytes, i32[0], j); |
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return j; |
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}, |
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/** |
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* Write one 32-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write32Bit": function (bytes, number, j) { |
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j = BitWriter["write24Bit"](bytes, number, j); |
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bytes[j++] = number >>> 24 & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 24-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write24Bit": function (bytes, number, j) { |
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j = BitWriter["write16Bit"](bytes, number, j); |
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bytes[j++] = number >>> 16 & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 16-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write16Bit": function (bytes, number, j) { |
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bytes[j++] = number & 0xFF; |
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bytes[j++] = number >>> 8 & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 16-bit float as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write16BitFloat": function (bytes, number, j) { |
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f32[0] = number; |
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let x = i32[0]; |
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let bits = (x >> 16) & 0x8000; |
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let m = (x >> 12) & 0x07ff; |
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let e = (x >> 23) & 0xff; |
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if (e >= 103) { |
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bits |= ((e - 112) << 10) | (m >> 1); |
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bits += m & 1; |
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} |
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bytes[j] = bits & 0xFF; |
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bytes[j+1] = bits >>> 8 & 0xFF; |
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return j+2; |
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}, |
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/** |
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* Write one 8-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
294
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* @param {number} j 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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"write8Bit": function (bytes, number, j) { |
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bytes[j++] = number & 0xFF; |
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return j; |
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}, |
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/** |
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* Write one 4-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
306
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* @param {number} j 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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"write4Bit": function (bytes, number, j) { |
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bytes[j++] = number & 0xF; |
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return j; |
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}, |
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314
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/** |
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* Write one 2-bit integer as a binary value. |
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* @param {!Array<number>} bytes An array of bytes. |
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* @param {number} number The number to write as bytes. |
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* @param {number} j 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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"write2Bit": function (bytes, number, j) { |
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bytes[j++] = number < 0 ? number + 4 : number; |
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return j; |
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}, |
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// 3-bit to 7-bit still need specific methods |
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"write3Bit": function (bytes, number, j) { |
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bytes[j++] = number < 0 ? number + Math.pow(2, 3) : number; |
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return j; |
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}, |
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"write5Bit": function (bytes, number, j) { |
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bytes[j++] = number < 0 ? number + Math.pow(2, 5) : number; |
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return j; |
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}, |
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"write6Bit": function (bytes, number, j) { |
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bytes[j++] = number < 0 ? number + Math.pow(2, 6) : number; |
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return j; |
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}, |
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"write7Bit": function (bytes, number, j) { |
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bytes[j++] = number < 0 ? number + Math.pow(2, 7) : number; |
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return j; |
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}, |
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344
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/** |
345
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* Write one boolean as a binary value. |
346
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|
* @param {!Array<number>} bytes An array of bytes. |
347
|
|
|
* @param {number} number The number to write as bytes. |
348
|
|
|
* @param {number} j The index being written in the byte buffer. |
349
|
|
|
* @return {number} The next index to write on the byte buffer. |
350
|
|
|
*/ |
351
|
|
|
"write1Bit": function (bytes, number, j) { |
352
|
|
|
bytes[j++] = number ? 1 : 0; |
353
|
|
|
return j; |
354
|
|
|
}, |
355
|
|
|
|
356
|
|
|
/** |
357
|
|
|
* Write one char as a byte. |
358
|
|
|
* @param {!Array<number>} bytes An array of bytes. |
359
|
|
|
* @param {string} string The string to write as bytes. |
360
|
|
|
* @param {number} j The index being written in the byte buffer. |
361
|
|
|
* @return {number} The next index to write on the byte buffer. |
362
|
|
|
*/ |
363
|
|
|
"writeString": function (bytes, string, j) { |
364
|
|
|
bytes[j++] = string.charCodeAt(0); |
365
|
|
|
return j; |
366
|
|
|
} |
367
|
|
|
}; |
368
|
|
|
|
369
|
|
|
/** |
370
|
|
|
* Get a binary string representation of a value described as bytes. |
371
|
|
|
* @param {Array<number>|number} bytes The bytes. |
372
|
|
|
* @return {string} |
373
|
|
|
*/ |
374
|
|
|
function getBinary(bytes) { |
375
|
|
|
let binary = ""; |
376
|
|
|
let i = 0; |
377
|
|
|
let bytesLength = bytes.length; |
378
|
|
|
while(i < bytesLength) { |
379
|
|
|
let bits = bytes[i].toString(2); |
380
|
|
|
binary = Array(9 - bits.length).join("0") + bits + binary; |
381
|
|
|
i++; |
382
|
|
|
} |
383
|
|
|
return binary; |
384
|
|
|
} |
385
|
|
|
|
386
|
|
|
/** |
387
|
|
|
* Read a group of bytes by turning it to bits. |
388
|
|
|
* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
389
|
|
|
* @param {number} i The index to read. |
390
|
|
|
* @param {number} numBytes The number of bytes |
391
|
|
|
* (1 for 8-bit, 2 for 16-bit, etc). |
392
|
|
|
* @return {number} |
393
|
|
|
*/ |
394
|
|
|
function readBytesAsBits(bytes, i, numBytes) { |
395
|
|
|
let j = numBytes-1; |
396
|
|
|
let byte = ""; |
397
|
|
|
while (j >= 0) { |
398
|
|
|
let bits = bytes[j + i].toString(2); |
399
|
|
|
byte += Array(9 - bits.length).join("0") + bits; |
400
|
|
|
j--; |
401
|
|
|
} |
402
|
|
|
return parseInt(byte, 2); |
403
|
|
|
} |
404
|
|
|
|
405
|
|
|
exports.BitWriter = BitWriter; |
406
|
|
|
exports.BitReader = BitReader; |
407
|
|
|
|