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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 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 byte buffer into what the bytes represent. |
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* @param {!Array<number>|Uint8Array} buffer An array of bytes. |
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* @param {number} bitDepth The bit depth of the data. |
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* Possible values are 1, 2, 4, 8, 16, 24, 32, 40, 48 or 64. |
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* @param {Object} options The options. They are: |
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* - "signed": If the numbers are signed. Default is false (unsigned). |
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* - "float": True for floating point numbers. Default is false. |
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* This option is available for 16, 32 and 64-bit numbers. |
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* - "base": The base of the input. Default is 10. Can be 2, 10 or 16. |
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* - "char": If the bytes represent a string. Default is false. |
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* - "be": If the values are big endian. Default is false (little endian). |
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* - "single": If it should return a single value instead of an array. |
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* Default is false. |
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* @return {!Array<number>|string} |
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*/ |
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function fromBytes(buffer, bitDepth, options={}) { |
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let base = 10; |
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if ("base" in options) { |
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base = options.base; |
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} |
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if (options.be) { |
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endianness.endianness(buffer, bitDepth / 8); |
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} |
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bytesToInt(buffer, base); |
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let bitReader = getBitReader(bitDepth, options.float, options.char); |
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let values = readBytes(buffer, bitDepth, options.signed, bitReader); |
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if (options.char) { |
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values = values.join(""); |
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} |
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if (options.single) { |
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values = values[0]; |
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} |
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return values; |
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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} isSigned True if the values should be signed. |
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* @param {Function} bitReader The function to read the bytes. |
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* @return {!Array<number>|string} |
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*/ |
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function readBytes(bytes, bitDepth, isSigned, bitReader) { |
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let values = []; |
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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.BitDepthMaxValues[bitDepth]; |
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let signFunction = isSigned ? signed : function(x,y){return x;}; |
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while (i < len) { |
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values[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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return values; |
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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 bitReader; |
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if (isChar) { |
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bitReader = reader.readChar; |
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} else { |
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bitReader = reader[getReaderFunctionName(bitDepth, isFloat)]; |
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} |
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return bitReader; |
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} |
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/** |
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* Build a bit reading function name based on the arguments. |
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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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* @return {string} |
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*/ |
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function getReaderFunctionName(bitDepth, isFloat) { |
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return 'read' + |
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((bitDepth == 2 || bitDepth == 4) ? 8 : bitDepth) + |
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'Bit' + |
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(isFloat ? "Float" : ""); |
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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
This check looks for parameters in functions that are not used in the function body and are not followed by other parameters which are used inside the function.