/*
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* Copyright 2012 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 "ZXBitArray.h"
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#import "ZXEAN13Reader.h"
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#import "ZXErrors.h"
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#import "ZXIntArray.h"
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// For an EAN-13 barcode, the first digit is represented by the parities used
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// to encode the next six digits, according to the table below. For example,
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// if the barcode is 5 123456 789012 then the value of the first digit is
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// signified by using odd for '1', even for '2', even for '3', odd for '4',
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// odd for '5', and even for '6'. See http://en.wikipedia.org/wiki/EAN-13
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//
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// Parity of next 6 digits
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// Digit 0 1 2 3 4 5
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// 0 Odd Odd Odd Odd Odd Odd
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// 1 Odd Odd Even Odd Even Even
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// 2 Odd Odd Even Even Odd Even
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// 3 Odd Odd Even Even Even Odd
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// 4 Odd Even Odd Odd Even Even
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// 5 Odd Even Even Odd Odd Even
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// 6 Odd Even Even Even Odd Odd
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// 7 Odd Even Odd Even Odd Even
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// 8 Odd Even Odd Even Even Odd
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// 9 Odd Even Even Odd Even Odd
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//
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// Note that the encoding for '0' uses the same parity as a UPC barcode. Hence
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// a UPC barcode can be converted to an EAN-13 barcode by prepending a 0.
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//
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// The encoding is represented by the following array, which is a bit pattern
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// using Odd = 0 and Even = 1. For example, 5 is represented by:
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//
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// Odd Even Even Odd Odd Even
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// in binary:
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// 0 1 1 0 0 1 == 0x19
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//
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const int ZX_EAN13_FIRST_DIGIT_ENCODINGS[] = {
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0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A
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};
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@interface ZXEAN13Reader ()
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@property (nonatomic, strong, readonly) ZXIntArray *decodeMiddleCounters;
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@end
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@implementation ZXEAN13Reader
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- (id)init {
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if (self = [super init]) {
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_decodeMiddleCounters = [[ZXIntArray alloc] initWithLength:4];
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}
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return self;
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}
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- (int)decodeMiddle:(ZXBitArray *)row startRange:(NSRange)startRange result:(NSMutableString *)result error:(NSError **)error {
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ZXIntArray *counters = self.decodeMiddleCounters;
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[counters clear];
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int end = row.size;
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int rowOffset = (int)NSMaxRange(startRange);
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int lgPatternFound = 0;
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for (int x = 0; x < 6 && rowOffset < end; x++) {
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int bestMatch = [ZXUPCEANReader decodeDigit:row counters:counters rowOffset:rowOffset patternType:ZX_UPC_EAN_PATTERNS_L_AND_G_PATTERNS error:error];
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if (bestMatch == -1) {
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return -1;
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}
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[result appendFormat:@"%C", (unichar)('0' + bestMatch % 10)];
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rowOffset += [counters sum];
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if (bestMatch >= 10) {
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lgPatternFound |= 1 << (5 - x);
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}
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}
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if (![self determineFirstDigit:result lgPatternFound:lgPatternFound]) {
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if (error) *error = ZXNotFoundErrorInstance();
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return -1;
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}
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NSRange middleRange = [[self class] findGuardPattern:row
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rowOffset:rowOffset
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whiteFirst:YES
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pattern:ZX_UPC_EAN_MIDDLE_PATTERN
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patternLen:ZX_UPC_EAN_MIDDLE_PATTERN_LEN
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error:error];
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if (middleRange.location == NSNotFound) {
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return -1;
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}
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rowOffset = (int)NSMaxRange(middleRange);
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for (int x = 0; x < 6 && rowOffset < end; x++) {
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int bestMatch = [ZXUPCEANReader decodeDigit:row
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counters:counters
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rowOffset:rowOffset
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patternType:ZX_UPC_EAN_PATTERNS_L_PATTERNS
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error:error];
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if (bestMatch == -1) {
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return -1;
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}
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[result appendFormat:@"%C", (unichar)('0' + bestMatch)];
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rowOffset += [counters sum];
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}
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return rowOffset;
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}
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- (ZXBarcodeFormat)barcodeFormat {
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return kBarcodeFormatEan13;
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}
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/**
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* Based on pattern of odd-even ('L' and 'G') patterns used to encoded the explicitly-encoded
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* digits in a barcode, determines the implicitly encoded first digit and adds it to the
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* result string.
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*
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* @param resultString string to insert decoded first digit into
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* @param lgPatternFound int whose bits indicates the pattern of odd/even L/G patterns used to
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* encode digits
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* @return NO if first digit cannot be determined
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*/
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- (BOOL)determineFirstDigit:(NSMutableString *)resultString lgPatternFound:(int)lgPatternFound {
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for (int d = 0; d < 10; d++) {
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if (lgPatternFound == ZX_EAN13_FIRST_DIGIT_ENCODINGS[d]) {
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[resultString insertString:[NSString stringWithFormat:@"%C", (unichar)('0' + d)] atIndex:0];
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return YES;
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}
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}
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return NO;
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}
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@end
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