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/* |
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* from-bytes: convert bytes to numbers and strings. |
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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 pad = require("../src/byte-padding.js"); |
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const endianness = require("endianness"); |
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const reader = require("../src/read-bytes.js"); |
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const bitDepths = require("../src/bit-depth.js"); |
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/** |
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* Turn a array of bytes into an array of what the bytes should represent. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} bitDepth The bitDepth. 1, 2, 4, 8, 16, 24, 32, 40, 48, 64. |
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* @param {Object} params The options. They are: |
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* - "signed", defaults to false |
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* - "float", defaults to false, true for floats. |
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* float is available for 16, 32 and 64 bit depths. |
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* - "base", defaults to 10, can be 2, 10 or 16 |
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* - "char", defaults to false, true for strings |
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* - "be", defaults to false, true for big endian |
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* @return {!Array<number>|string} The values represented in the bytes. |
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*/ |
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function fromBytes(bytes, bitDepth, params={}) { |
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let base = 10; |
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if ("base" in params) { |
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base = params.base; |
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} |
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if (params.be) { |
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endianness.endianness(bytes, bitDepth / 8); |
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} |
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return readBytes( |
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bytes, |
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bitDepth, |
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params.char, |
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params.signed, |
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params.float, |
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base); |
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} |
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/** |
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* Turn a array of bytes into an array of what the bytes should represent. |
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* @param {!Array<number>|Uint8Array} bytes An array of bytes. |
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* @param {number} bitDepth The bitDepth. 1, 2, 4, 8, 16, 24, 32, 40, 48, 64. |
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* @param {boolean} isChar True if it is a string. |
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* @param {boolean} isSigned True if the values should be signed. |
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* @param {boolean} isFloat True if the values are IEEE floating point numbers. |
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* @param {number} base The base, one of 2, 10 or 16. |
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* @return {!Array<number>|string} The values represented in the bytes. |
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*/ |
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function readBytes(bytes, bitDepth, isChar, isSigned, isFloat, base) { |
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let numbers = []; |
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let i = 0; |
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let j = 0; |
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let offset = bitDepths.bitDepthOffsets[bitDepth]; |
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let len = bytes.length - (offset -1); |
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let maxBitDepthValue = bitDepths.maxBitDepth[bitDepth]; |
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bytesToInt(bytes, base); |
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let bitReader = getBitReader(bitDepth, isFloat, isChar); |
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let signFunction = isSigned ? signed : function(x,y){return x;}; |
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while (i < len) { |
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numbers[j] = signFunction(bitReader(bytes, i), maxBitDepthValue); |
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i += offset; |
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j++; |
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} |
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if (isChar) { |
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numbers = numbers.join(""); |
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} |
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return numbers; |
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} |
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/** |
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* Return a function to read binary data. |
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* @param {number} bitDepth The bitDepth. 1, 2, 4, 8, 16, 24, 32, 40, 48, 64. |
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* @param {boolean} isFloat True if the values are IEEE floating point numbers. |
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* @param {boolean} isChar True if it is a string. |
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* @return {Function} |
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*/ |
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function getBitReader(bitDepth, isFloat, isChar) { |
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let readBitDepth = bitDepth; |
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if (bitDepth == 2 || bitDepth == 4) { |
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readBitDepth = 8; |
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} |
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if (isChar) { |
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return reader.readChar; |
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} else { |
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return reader['read' + readBitDepth + 'Bit' + (isFloat ? "Float" : "")]; |
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} |
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} |
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/** |
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* Turn bytes to base 10. |
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* @param {!Array<number>|Uint8Array} bytes The bytes as binary or hex strings. |
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* @param {number} base The base. |
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*/ |
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function bytesToInt(bytes, base) { |
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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] = parseInt(bytes[i], base); |
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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 a unsigned number to a signed number. |
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* @param {number} number The number. |
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* @param {number} maxValue The max range for the number bit depth. |
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*/ |
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function signed(number, maxValue) { |
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if (number > parseInt(maxValue / 2, 10) - 1) { |
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number -= maxValue; |
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} |
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return number; |
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} |
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module.exports.fromBytes = fromBytes; |
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rochars /
byte-data
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