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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 reader = require("../src/read-bytes.js"); |
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const bitDepths = require("../src/bit-depth.js"); |
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const helpers = require("../src/helpers.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>|!Array<string>|Uint8Array} buffer An array of bytes. |
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* @param {Object} type One of the available types. |
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* @return {!Array<number>|number|string} |
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*/ |
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function fromBytes(buffer, type) { |
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let bitDepth = type.bits; |
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helpers.fixFloat16Endianness(buffer, type); |
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helpers.makeBigEndian(buffer, type.be, bitDepth); |
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bytesToInt(buffer, type.base); |
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let values = readBytes( |
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buffer, |
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type, |
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getBitReader(type) |
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); |
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if (type.char) { |
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values = values.join(""); |
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} |
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if (type.single) { |
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values = getSingleValue(values, type); |
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} |
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return values; |
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} |
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/** |
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* Return the first value from the result value array. |
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* @param {!Array<number>|string} values The values. |
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* @param {Object} type One of the available types. |
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* @return {number|string} |
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*/ |
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function getSingleValue(values, type) { |
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if (type.char) { |
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values = values.slice(0, type.bits / 8); |
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} else { |
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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 {Object} type The type. |
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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, type, bitReader) { |
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let values = []; |
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let i = 0; |
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let offset = type.bits < 8 ? 1 : type.bits / 8; |
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let len = bytes.length - (offset -1); |
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let maxBitDepthValue = bitDepths.BitDepthMaxValues[type.bits]; |
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let signFunction = type.signed && !type.float ? |
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helpers.signed : function(x){return x;}; |
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while (i < len) { |
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values.push(signFunction(bitReader(bytes, i, type), maxBitDepthValue)); |
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i += offset; |
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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 {Object} type One of the available types. |
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* @return {Function} |
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*/ |
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function getBitReader(type) { |
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let bitReader; |
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if (type.char) { |
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bitReader = reader.readChar; |
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} else { |
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bitReader = reader[getReaderFunctionName(type.bits, type.float)]; |
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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} bits The bitDepth. 1, 2, 4, 8, 16, 24, 32, 40, 48, 64. |
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* @param {boolean} float 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(bits, float) { |
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return 'read' + (bits < 8 ? 8 : bits) + |
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'Bit' + (float ? "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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module.exports.fromBytes = fromBytes; |
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|
rochars /
byte-data
