77064f5e5e
* Split core lib into multiple files * Refactor data encoding methods * Refactor data masking process * Improve qr code generation process * Increase minimum required node version to 0.10 * Add linter * Add tests and tests coverage * Update travis config to fix compilation issues * Add examples folder * Add missing license tag in package.json * Update build script and add sourcemap support * Publish only strictly needed files on npm * Update readme
101 lines
3.4 KiB
JavaScript
Executable file
101 lines
3.4 KiB
JavaScript
Executable file
var Buffer = require('../utils/buffer')
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var Utils = require('./utils')
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var ECCode = require('./error-correction-code')
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var ECLevel = require('./error-correction-level')
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var ByteData = require('./byte-data')
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// Generator polynomial used to encode version information
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var G18 = (1 << 12) | (1 << 11) | (1 << 10) | (1 << 9) | (1 << 8) | (1 << 5) | (1 << 2) | (1 << 0)
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var G18_BCH = Utils.getBCHDigit(G18)
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var getBestVersionForDataLength = function getBestVersionForDataLength (length, errorCorrectionLevel) {
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for (var currentVersion = 1; currentVersion <= 40; currentVersion++) {
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if (length <= exports.getCapacity(currentVersion, errorCorrectionLevel)) return currentVersion
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}
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return undefined
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}
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/**
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* Check if QR Code version is valid
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*
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* @param {Number} version QR Code version
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* @return {Boolean} true if valid version, false otherwise
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*/
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exports.isValidVersion = function isValidVersion (version) {
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return !isNaN(version) && version >= 1 && version <= 40
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}
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/**
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* Returns how much data can be stored with the specified QR code version
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* and error correction level
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*
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* @param {Number} version QR Code version (1-40)
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* @param {Number} errorCorrectionLevel Error correction level
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* @return {Number} Quantity of storable data
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*/
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exports.getCapacity = function getCapacity (version, errorCorrectionLevel) {
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if (!exports.isValidVersion(version)) {
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throw new Error('Invalid QR Code version')
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}
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// Total codewords for this QR code version (Data + Error correction)
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var totalCodewords = Utils.getSymbolTotalCodewords(version)
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// Total number of error correction codewords
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var ecTotalCodewords = ECCode.getTotalCodewordsCount(version, errorCorrectionLevel)
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// Total number of data codewords
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var dataTotalCodewordsBits = (totalCodewords - ecTotalCodewords) * 8
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// Character count indicator + mode indicator bits
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var reservedBits = ByteData.getCharCountIndicator(version) + 4
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// Return max number of storable codewords
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return Math.floor((dataTotalCodewordsBits - reservedBits) / 8)
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}
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/**
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* Returns the minimum version needed to contain the amount of data
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*
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* @param {Buffer, Array, ByteData} data Data buffer
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* @param {Number} [errorCorrectionLevel=H] Error correction level
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* @return {Number} QR Code version
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*/
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exports.getBestVersionForData = function getBestVersionForData (data, errorCorrectionLevel) {
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var dataLength
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if (data instanceof ByteData) dataLength = data.getLength()
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else if (Buffer.isBuffer(data)) dataLength = data.length
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else dataLength = new Buffer(data).length
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var ecl = errorCorrectionLevel
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if (typeof ecl === 'undefined') ecl = ECLevel.H
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return getBestVersionForDataLength(dataLength, ecl)
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}
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/**
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* Returns version information with relative error correction bits
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*
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* The version information is included in QR Code symbols of version 7 or larger.
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* It consists of an 18-bit sequence containing 6 data bits,
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* with 12 error correction bits calculated using the (18, 6) Golay code.
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*
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* @param {Number} version QR Code version
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* @return {Number} Encoded version info bits
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*/
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exports.getEncodedBits = function getEncodedBits (version) {
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if (!exports.isValidVersion(version) || version < 7) {
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throw new Error('Invalid QR Code version')
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}
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var d = version << 12
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while (Utils.getBCHDigit(d) - G18_BCH >= 0) {
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d ^= (G18 << (Utils.getBCHDigit(d) - G18_BCH))
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}
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return (version << 12) | d
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}
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