const Utils = require('./utils')
|
const ECCode = require('./error-correction-code')
|
const ECLevel = require('./error-correction-level')
|
const Mode = require('./mode')
|
const VersionCheck = require('./version-check')
|
|
// Generator polynomial used to encode version information
|
const G18 = (1 << 12) | (1 << 11) | (1 << 10) | (1 << 9) | (1 << 8) | (1 << 5) | (1 << 2) | (1 << 0)
|
const G18_BCH = Utils.getBCHDigit(G18)
|
|
function getBestVersionForDataLength (mode, length, errorCorrectionLevel) {
|
for (let currentVersion = 1; currentVersion <= 40; currentVersion++) {
|
if (length <= exports.getCapacity(currentVersion, errorCorrectionLevel, mode)) {
|
return currentVersion
|
}
|
}
|
|
return undefined
|
}
|
|
function getReservedBitsCount (mode, version) {
|
// Character count indicator + mode indicator bits
|
return Mode.getCharCountIndicator(mode, version) + 4
|
}
|
|
function getTotalBitsFromDataArray (segments, version) {
|
let totalBits = 0
|
|
segments.forEach(function (data) {
|
const reservedBits = getReservedBitsCount(data.mode, version)
|
totalBits += reservedBits + data.getBitsLength()
|
})
|
|
return totalBits
|
}
|
|
function getBestVersionForMixedData (segments, errorCorrectionLevel) {
|
for (let currentVersion = 1; currentVersion <= 40; currentVersion++) {
|
const length = getTotalBitsFromDataArray(segments, currentVersion)
|
if (length <= exports.getCapacity(currentVersion, errorCorrectionLevel, Mode.MIXED)) {
|
return currentVersion
|
}
|
}
|
|
return undefined
|
}
|
|
/**
|
* Returns version number from a value.
|
* If value is not a valid version, returns defaultValue
|
*
|
* @param {Number|String} value QR Code version
|
* @param {Number} defaultValue Fallback value
|
* @return {Number} QR Code version number
|
*/
|
exports.from = function from (value, defaultValue) {
|
if (VersionCheck.isValid(value)) {
|
return parseInt(value, 10)
|
}
|
|
return defaultValue
|
}
|
|
/**
|
* Returns how much data can be stored with the specified QR code version
|
* and error correction level
|
*
|
* @param {Number} version QR Code version (1-40)
|
* @param {Number} errorCorrectionLevel Error correction level
|
* @param {Mode} mode Data mode
|
* @return {Number} Quantity of storable data
|
*/
|
exports.getCapacity = function getCapacity (version, errorCorrectionLevel, mode) {
|
if (!VersionCheck.isValid(version)) {
|
throw new Error('Invalid QR Code version')
|
}
|
|
// Use Byte mode as default
|
if (typeof mode === 'undefined') mode = Mode.BYTE
|
|
// Total codewords for this QR code version (Data + Error correction)
|
const totalCodewords = Utils.getSymbolTotalCodewords(version)
|
|
// Total number of error correction codewords
|
const ecTotalCodewords = ECCode.getTotalCodewordsCount(version, errorCorrectionLevel)
|
|
// Total number of data codewords
|
const dataTotalCodewordsBits = (totalCodewords - ecTotalCodewords) * 8
|
|
if (mode === Mode.MIXED) return dataTotalCodewordsBits
|
|
const usableBits = dataTotalCodewordsBits - getReservedBitsCount(mode, version)
|
|
// Return max number of storable codewords
|
switch (mode) {
|
case Mode.NUMERIC:
|
return Math.floor((usableBits / 10) * 3)
|
|
case Mode.ALPHANUMERIC:
|
return Math.floor((usableBits / 11) * 2)
|
|
case Mode.KANJI:
|
return Math.floor(usableBits / 13)
|
|
case Mode.BYTE:
|
default:
|
return Math.floor(usableBits / 8)
|
}
|
}
|
|
/**
|
* Returns the minimum version needed to contain the amount of data
|
*
|
* @param {Segment} data Segment of data
|
* @param {Number} [errorCorrectionLevel=H] Error correction level
|
* @param {Mode} mode Data mode
|
* @return {Number} QR Code version
|
*/
|
exports.getBestVersionForData = function getBestVersionForData (data, errorCorrectionLevel) {
|
let seg
|
|
const ecl = ECLevel.from(errorCorrectionLevel, ECLevel.M)
|
|
if (Array.isArray(data)) {
|
if (data.length > 1) {
|
return getBestVersionForMixedData(data, ecl)
|
}
|
|
if (data.length === 0) {
|
return 1
|
}
|
|
seg = data[0]
|
} else {
|
seg = data
|
}
|
|
return getBestVersionForDataLength(seg.mode, seg.getLength(), ecl)
|
}
|
|
/**
|
* Returns version information with relative error correction bits
|
*
|
* The version information is included in QR Code symbols of version 7 or larger.
|
* It consists of an 18-bit sequence containing 6 data bits,
|
* with 12 error correction bits calculated using the (18, 6) Golay code.
|
*
|
* @param {Number} version QR Code version
|
* @return {Number} Encoded version info bits
|
*/
|
exports.getEncodedBits = function getEncodedBits (version) {
|
if (!VersionCheck.isValid(version) || version < 7) {
|
throw new Error('Invalid QR Code version')
|
}
|
|
let d = version << 12
|
|
while (Utils.getBCHDigit(d) - G18_BCH >= 0) {
|
d ^= (G18 << (Utils.getBCHDigit(d) - G18_BCH))
|
}
|
|
return (version << 12) | d
|
}
|
