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/** |
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* helpers: Functions to work with bytes and byte arrays. |
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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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*/ |
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const endianness = require("endianness"); |
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let Type = require("../src/type"); |
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/** |
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* Padding for binary strings. |
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* @param {!Array<string>} bytes The bytes as binary strings. |
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* @param {number} base The base. |
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* @param {number} index The byte to pad. |
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*/ |
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function padding(bytes, base, index) { |
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bytes[index] = bytePadding(bytes[index], base); |
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} |
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/** |
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* Padding with 0s for byte strings. |
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* @param {string} theByte The byte as a binary or hex string. |
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* @param {number} base The base. |
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* @returns {string} The padded byte. |
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*/ |
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function bytePadding(theByte, base) { |
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let offset = theByte.length + 1; |
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if (base == 2) { |
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offset = 8; |
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} else if (base == 16) { |
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offset = 2; |
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} |
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return lPadZeros(theByte, offset); |
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} |
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/** |
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* Fix the size of nibbles. |
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* @param {!Array<string>} nibbles The nibble as a binary or hex string. |
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* @param {number} base The base. |
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* @param {number} index The nibble offset. |
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*/ |
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function paddingNibble(nibbles, base, index) { |
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if (base == 2 && nibbles[index].length < 4) { |
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nibbles[index] = |
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new Array((5 - nibbles[index].length)).join("0") + nibbles[index]; |
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} |
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} |
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/** |
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* Fix the size of crumbs. |
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* @param {!Array<string>} crumbs The nibble as a binary or hex string. |
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* @param {number} base The base. |
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* @param {number} index The nibble offset. |
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*/ |
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function paddingCrumb(crumbs, base, index) { |
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if ((base == 2 || base == 16) && crumbs[index].length < 2) { |
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crumbs[index] = '0' + crumbs[index]; |
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} |
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} |
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/** |
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* Pad a string with zeros to the left. |
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* TODO: This should support both arrays and strings. |
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* @param {string} value The string (representing a binary or hex value). |
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* @param {number} numZeros the max number of zeros. |
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* For 1 binary byte string it should be 8. |
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*/ |
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function lPadZeros(value, numZeros) { |
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while (value.length < numZeros) { |
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value = '0' + value; |
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} |
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return value; |
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} |
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/** |
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* Swap the endianness to big endian. |
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* @param {!Array<number>} bytes The values. |
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* @param {Object} type The type. |
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*/ |
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function makeBigEndian(bytes, type) { |
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if (type.be) { |
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endianness(bytes, type.offset); |
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} |
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} |
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/** |
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* Turn bytes to base 2, 10 or 16. |
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* @param {!Array<string>|!Array<number>} bytes The bytes. |
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* @param {number} base The base. |
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* @param {Function} padFunction The function to use for padding. |
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*/ |
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function bytesToBase(bytes, base, padFunction=padding) { |
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if (base != 10) { |
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let i = 0; |
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let len = bytes.length; |
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while (i < len) { |
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bytes[i] = bytes[i].toString(base); |
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padFunction(bytes, base, i); |
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i++; |
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} |
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} |
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} |
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/** |
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* Turn the output to the correct base. |
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* @param {!Array<number>} bytes The bytes. |
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* @param {number} bitDepth The bit depth of the data. |
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* @param {number} base The desired base for the output data. |
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*/ |
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function outputToBase(bytes, bitDepth, base) { |
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if (bitDepth == 4) { |
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bytesToBase(bytes, base, paddingNibble); |
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} else if (bitDepth == 2) { |
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bytesToBase(bytes, base, paddingCrumb); |
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} else if(bitDepth == 1) { |
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bytesToBase(bytes, base, function(){}); |
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}else { |
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bytesToBase(bytes, base); |
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} |
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} |
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/** |
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* Get the full type spec for the reading/writing. |
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* @param {Object} atype One of the available types. |
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* @param {number} base The base of the input. |
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* @param {boolean} single True if its a single value, false for array. |
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* @return {Object} |
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*/ |
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function getType(atype, base, single) { |
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let theType = Object.assign(new Type({}), atype); |
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theType.base = base; |
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theType.single = single; |
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return theType; |
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} |
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/** |
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* Make a single value an array in case it is not. |
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* If the value is a string it stays a string. |
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* @param {!Array<number>|number|string} values The value or values. |
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* @return {!Array<number>|string} |
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*/ |
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function turnToArray(values) { |
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if (!Array.isArray(values) && typeof values != "string") { |
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values = [values]; |
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} |
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return values; |
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} |
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module.exports.makeBigEndian = makeBigEndian; |
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module.exports.outputToBase = outputToBase; |
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module.exports.padding = padding; |
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module.exports.paddingNibble = paddingNibble; |
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module.exports.paddingCrumb = paddingCrumb; |
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module.exports.bytePadding = bytePadding; |
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module.exports.lPadZeros = lPadZeros; |
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module.exports.getType = getType; |
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module.exports.turnToArray = turnToArray; |
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rochars /
byte-data
