122 lines
3.8 KiB
JavaScript
122 lines
3.8 KiB
JavaScript
/*
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Ported to JavaScript by Lazar Laszlo 2011
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lazarsoft@gmail.com, www.lazarsoft.info
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*/
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/*
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*
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* Copyright 2007 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import {URShift} from './qrcode';
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import ErrorCorrectionLevel from './errorlevel';
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var FORMAT_INFO_MASK_QR = 0x5412;
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var FORMAT_INFO_DECODE_LOOKUP = [
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[0x5412, 0x00],
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[0x5125, 0x01],
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[0x5E7C, 0x02],
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[0x5B4B, 0x03],
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[0x45F9, 0x04],
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[0x40CE, 0x05],
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[0x4F97, 0x06],
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[0x4AA0, 0x07],
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[0x77C4, 0x08],
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[0x72F3, 0x09],
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[0x7DAA, 0x0A],
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[0x789D, 0x0B],
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[0x662F, 0x0C],
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[0x6318, 0x0D],
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[0x6C41, 0x0E],
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[0x6976, 0x0F],
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[0x1689, 0x10],
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[0x13BE, 0x11],
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[0x1CE7, 0x12],
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[0x19D0, 0x13],
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[0x0762, 0x14],
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[0x0255, 0x15],
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[0x0D0C, 0x16],
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[0x083B, 0x17],
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[0x355F, 0x18],
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[0x3068, 0x19],
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[0x3F31, 0x1A],
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[0x3A06, 0x1B],
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[0x24B4, 0x1C],
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[0x2183, 0x1D],
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[0x2EDA, 0x1E],
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[0x2BED, 0x1F],
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];
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var BITS_SET_IN_HALF_BYTE = [0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4];
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export default function FormatInformation(formatInfo) {
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this.errorCorrectionLevel = ErrorCorrectionLevel.forBits((formatInfo >> 3) & 0x03);
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this.dataMask = (formatInfo & 0x07);
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}
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FormatInformation.prototype.GetHashCode = function() {
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return (this.errorCorrectionLevel.ordinal() << 3) | this.dataMask;
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};
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FormatInformation.prototype.Equals = function(o) {
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var other = o;
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return this.errorCorrectionLevel == other.errorCorrectionLevel && this.dataMask == other.dataMask;
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};
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FormatInformation.numBitsDiffering = function(a, b) {
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a ^= b; // a now has a 1 bit exactly where its bit differs with b's
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// Count bits set quickly with a series of lookups:
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return BITS_SET_IN_HALF_BYTE[a & 0x0F] + BITS_SET_IN_HALF_BYTE[(URShift(a, 4) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 8) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 12) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 16) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 20) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 24) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(URShift(a, 28) & 0x0F)];
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};
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FormatInformation.decodeFormatInformation = function(maskedFormatInfo) {
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var formatInfo = FormatInformation.doDecodeFormatInformation(maskedFormatInfo);
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if (formatInfo != null) {
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return formatInfo;
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}
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// Should return null, but, some QR codes apparently
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// do not mask this info. Try again by actually masking the pattern
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// first
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return FormatInformation.doDecodeFormatInformation(maskedFormatInfo ^ FORMAT_INFO_MASK_QR);
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};
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FormatInformation.doDecodeFormatInformation = function(maskedFormatInfo) {
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// Find the int in FORMAT_INFO_DECODE_LOOKUP with fewest bits differing
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var bestDifference = 0xffffffff;
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var bestFormatInfo = 0;
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for (var i = 0; i < FORMAT_INFO_DECODE_LOOKUP.length; i++) {
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var decodeInfo = FORMAT_INFO_DECODE_LOOKUP[i];
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var targetInfo = decodeInfo[0];
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if (targetInfo == maskedFormatInfo) {
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// Found an exact match
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return new FormatInformation(decodeInfo[1]);
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}
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var bitsDifference = this.numBitsDiffering(maskedFormatInfo, targetInfo);
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if (bitsDifference < bestDifference) {
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bestFormatInfo = decodeInfo[1];
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bestDifference = bitsDifference;
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}
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}
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// Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits
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// differing means we found a match
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if (bestDifference <= 3) {
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return new FormatInformation(bestFormatInfo);
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}
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return null;
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};
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