330 lines
9.1 KiB
JavaScript
330 lines
9.1 KiB
JavaScript
const Mode = require('./mode')
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const NumericData = require('./numeric-data')
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const AlphanumericData = require('./alphanumeric-data')
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const ByteData = require('./byte-data')
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const KanjiData = require('./kanji-data')
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const Regex = require('./regex')
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const Utils = require('./utils')
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const dijkstra = require('dijkstrajs')
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/**
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* Returns UTF8 byte length
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*
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* @param {String} str Input string
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* @return {Number} Number of byte
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*/
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function getStringByteLength (str) {
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return unescape(encodeURIComponent(str)).length
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}
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/**
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* Get a list of segments of the specified mode
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* from a string
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*
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* @param {Mode} mode Segment mode
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* @param {String} str String to process
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* @return {Array} Array of object with segments data
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*/
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function getSegments (regex, mode, str) {
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const segments = []
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let result
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while ((result = regex.exec(str)) !== null) {
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segments.push({
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data: result[0],
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index: result.index,
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mode: mode,
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length: result[0].length
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})
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}
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return segments
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}
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/**
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* Extracts a series of segments with the appropriate
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* modes from a string
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*
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* @param {String} dataStr Input string
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* @return {Array} Array of object with segments data
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*/
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function getSegmentsFromString (dataStr) {
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const numSegs = getSegments(Regex.NUMERIC, Mode.NUMERIC, dataStr)
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const alphaNumSegs = getSegments(Regex.ALPHANUMERIC, Mode.ALPHANUMERIC, dataStr)
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let byteSegs
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let kanjiSegs
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if (Utils.isKanjiModeEnabled()) {
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byteSegs = getSegments(Regex.BYTE, Mode.BYTE, dataStr)
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kanjiSegs = getSegments(Regex.KANJI, Mode.KANJI, dataStr)
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} else {
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byteSegs = getSegments(Regex.BYTE_KANJI, Mode.BYTE, dataStr)
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kanjiSegs = []
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}
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const segs = numSegs.concat(alphaNumSegs, byteSegs, kanjiSegs)
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return segs
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.sort(function (s1, s2) {
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return s1.index - s2.index
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})
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.map(function (obj) {
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return {
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data: obj.data,
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mode: obj.mode,
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length: obj.length
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}
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})
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}
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/**
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* Returns how many bits are needed to encode a string of
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* specified length with the specified mode
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*
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* @param {Number} length String length
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* @param {Mode} mode Segment mode
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* @return {Number} Bit length
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*/
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function getSegmentBitsLength (length, mode) {
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switch (mode) {
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case Mode.NUMERIC:
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return NumericData.getBitsLength(length)
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case Mode.ALPHANUMERIC:
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return AlphanumericData.getBitsLength(length)
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case Mode.KANJI:
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return KanjiData.getBitsLength(length)
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case Mode.BYTE:
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return ByteData.getBitsLength(length)
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}
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}
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/**
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* Merges adjacent segments which have the same mode
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*
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* @param {Array} segs Array of object with segments data
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* @return {Array} Array of object with segments data
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*/
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function mergeSegments (segs) {
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return segs.reduce(function (acc, curr) {
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const prevSeg = acc.length - 1 >= 0 ? acc[acc.length - 1] : null
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if (prevSeg && prevSeg.mode === curr.mode) {
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acc[acc.length - 1].data += curr.data
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return acc
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}
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acc.push(curr)
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return acc
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}, [])
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}
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/**
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* Generates a list of all possible nodes combination which
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* will be used to build a segments graph.
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*
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* Nodes are divided by groups. Each group will contain a list of all the modes
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* in which is possible to encode the given text.
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*
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* For example the text '12345' can be encoded as Numeric, Alphanumeric or Byte.
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* The group for '12345' will contain then 3 objects, one for each
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* possible encoding mode.
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*
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* Each node represents a possible segment.
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*
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* @param {Array} segs Array of object with segments data
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* @return {Array} Array of object with segments data
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*/
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function buildNodes (segs) {
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const nodes = []
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for (let i = 0; i < segs.length; i++) {
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const seg = segs[i]
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switch (seg.mode) {
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case Mode.NUMERIC:
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nodes.push([seg,
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{ data: seg.data, mode: Mode.ALPHANUMERIC, length: seg.length },
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{ data: seg.data, mode: Mode.BYTE, length: seg.length }
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])
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break
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case Mode.ALPHANUMERIC:
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nodes.push([seg,
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{ data: seg.data, mode: Mode.BYTE, length: seg.length }
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])
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break
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case Mode.KANJI:
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nodes.push([seg,
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{ data: seg.data, mode: Mode.BYTE, length: getStringByteLength(seg.data) }
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])
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break
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case Mode.BYTE:
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nodes.push([
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{ data: seg.data, mode: Mode.BYTE, length: getStringByteLength(seg.data) }
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])
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}
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}
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return nodes
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}
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/**
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* Builds a graph from a list of nodes.
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* All segments in each node group will be connected with all the segments of
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* the next group and so on.
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*
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* At each connection will be assigned a weight depending on the
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* segment's byte length.
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*
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* @param {Array} nodes Array of object with segments data
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* @param {Number} version QR Code version
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* @return {Object} Graph of all possible segments
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*/
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function buildGraph (nodes, version) {
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const table = {}
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const graph = { start: {} }
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let prevNodeIds = ['start']
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for (let i = 0; i < nodes.length; i++) {
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const nodeGroup = nodes[i]
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const currentNodeIds = []
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for (let j = 0; j < nodeGroup.length; j++) {
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const node = nodeGroup[j]
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const key = '' + i + j
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currentNodeIds.push(key)
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table[key] = { node: node, lastCount: 0 }
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graph[key] = {}
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for (let n = 0; n < prevNodeIds.length; n++) {
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const prevNodeId = prevNodeIds[n]
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if (table[prevNodeId] && table[prevNodeId].node.mode === node.mode) {
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graph[prevNodeId][key] =
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getSegmentBitsLength(table[prevNodeId].lastCount + node.length, node.mode) -
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getSegmentBitsLength(table[prevNodeId].lastCount, node.mode)
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table[prevNodeId].lastCount += node.length
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} else {
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if (table[prevNodeId]) table[prevNodeId].lastCount = node.length
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graph[prevNodeId][key] = getSegmentBitsLength(node.length, node.mode) +
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4 + Mode.getCharCountIndicator(node.mode, version) // switch cost
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}
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}
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}
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prevNodeIds = currentNodeIds
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}
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for (let n = 0; n < prevNodeIds.length; n++) {
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graph[prevNodeIds[n]].end = 0
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}
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return { map: graph, table: table }
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}
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/**
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* Builds a segment from a specified data and mode.
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* If a mode is not specified, the more suitable will be used.
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*
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* @param {String} data Input data
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* @param {Mode | String} modesHint Data mode
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* @return {Segment} Segment
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*/
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function buildSingleSegment (data, modesHint) {
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let mode
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const bestMode = Mode.getBestModeForData(data)
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mode = Mode.from(modesHint, bestMode)
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// Make sure data can be encoded
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if (mode !== Mode.BYTE && mode.bit < bestMode.bit) {
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throw new Error('"' + data + '"' +
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' cannot be encoded with mode ' + Mode.toString(mode) +
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'.\n Suggested mode is: ' + Mode.toString(bestMode))
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}
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// Use Mode.BYTE if Kanji support is disabled
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if (mode === Mode.KANJI && !Utils.isKanjiModeEnabled()) {
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mode = Mode.BYTE
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}
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switch (mode) {
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case Mode.NUMERIC:
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return new NumericData(data)
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case Mode.ALPHANUMERIC:
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return new AlphanumericData(data)
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case Mode.KANJI:
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return new KanjiData(data)
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case Mode.BYTE:
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return new ByteData(data)
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}
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}
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/**
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* Builds a list of segments from an array.
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* Array can contain Strings or Objects with segment's info.
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*
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* For each item which is a string, will be generated a segment with the given
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* string and the more appropriate encoding mode.
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*
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* For each item which is an object, will be generated a segment with the given
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* data and mode.
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* Objects must contain at least the property "data".
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* If property "mode" is not present, the more suitable mode will be used.
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*
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* @param {Array} array Array of objects with segments data
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* @return {Array} Array of Segments
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*/
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exports.fromArray = function fromArray (array) {
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return array.reduce(function (acc, seg) {
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if (typeof seg === 'string') {
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acc.push(buildSingleSegment(seg, null))
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} else if (seg.data) {
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acc.push(buildSingleSegment(seg.data, seg.mode))
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}
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return acc
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}, [])
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}
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/**
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* Builds an optimized sequence of segments from a string,
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* which will produce the shortest possible bitstream.
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*
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* @param {String} data Input string
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* @param {Number} version QR Code version
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* @return {Array} Array of segments
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*/
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exports.fromString = function fromString (data, version) {
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const segs = getSegmentsFromString(data, Utils.isKanjiModeEnabled())
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const nodes = buildNodes(segs)
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const graph = buildGraph(nodes, version)
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const path = dijkstra.find_path(graph.map, 'start', 'end')
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const optimizedSegs = []
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for (let i = 1; i < path.length - 1; i++) {
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optimizedSegs.push(graph.table[path[i]].node)
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}
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return exports.fromArray(mergeSegments(optimizedSegs))
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}
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/**
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* Splits a string in various segments with the modes which
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* best represent their content.
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* The produced segments are far from being optimized.
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* The output of this function is only used to estimate a QR Code version
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* which may contain the data.
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*
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* @param {string} data Input string
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* @return {Array} Array of segments
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*/
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exports.rawSplit = function rawSplit (data) {
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return exports.fromArray(
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getSegmentsFromString(data, Utils.isKanjiModeEnabled())
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)
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}
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