ZXingObjC/datamatrix/encoder/ZXDataMatrixErrorCorrection.m

/*
 * Copyright 2013 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#import "ZXDataMatrixErrorCorrection.h"
#import "ZXSymbolInfo.h"

/**
 * Lookup table which factors to use for which number of error correction codewords.
 * See FACTORS.
 */
const int FACTOR_SETS_LEN = 16;
const int FACTOR_SETS[FACTOR_SETS_LEN] = {5, 7, 10, 11, 12, 14, 18, 20, 24, 28, 36, 42, 48, 56, 62, 68};

/**
 * Precomputed polynomial factors for ECC 200.
 */
const int FACTORS[16][68] = {
  {228, 48, 15, 111, 62},
  {23, 68, 144, 134, 240, 92, 254},
  {28, 24, 185, 166, 223, 248, 116, 255, 110, 61},
  {175, 138, 205, 12, 194, 168, 39, 245, 60, 97, 120},
  {41, 153, 158, 91, 61, 42, 142, 213, 97, 178, 100, 242},
  {156, 97, 192, 252, 95, 9, 157, 119, 138, 45, 18, 186, 83, 185},
  {83, 195, 100, 39, 188, 75, 66, 61, 241, 213, 109, 129, 94, 254, 225, 48, 90, 188},
  {15, 195, 244, 9, 233, 71, 168, 2, 188, 160, 153, 145, 253, 79, 108, 82, 27, 174, 186, 172},
  {52, 190, 88, 205, 109, 39, 176, 21, 155, 197, 251, 223, 155, 21, 5, 172,
    254, 124, 12, 181, 184, 96, 50, 193},
  {211, 231, 43, 97, 71, 96, 103, 174, 37, 151, 170, 53, 75, 34, 249, 121,
    17, 138, 110, 213, 141, 136, 120, 151, 233, 168, 93, 255},
  {245, 127, 242, 218, 130, 250, 162, 181, 102, 120, 84, 179, 220, 251, 80, 182,
    229, 18, 2, 4, 68, 33, 101, 137, 95, 119, 115, 44, 175, 184, 59, 25,
    225, 98, 81, 112},
  {77, 193, 137, 31, 19, 38, 22, 153, 247, 105, 122, 2, 245, 133, 242, 8,
    175, 95, 100, 9, 167, 105, 214, 111, 57, 121, 21, 1, 253, 57, 54, 101,
    248, 202, 69, 50, 150, 177, 226, 5, 9, 5},
  {245, 132, 172, 223, 96, 32, 117, 22, 238, 133, 238, 231, 205, 188, 237, 87,
    191, 106, 16, 147, 118, 23, 37, 90, 170, 205, 131, 88, 120, 100, 66, 138,
    186, 240, 82, 44, 176, 87, 187, 147, 160, 175, 69, 213, 92, 253, 225, 19},
  {175, 9, 223, 238, 12, 17, 220, 208, 100, 29, 175, 170, 230, 192, 215, 235,
    150, 159, 36, 223, 38, 200, 132, 54, 228, 146, 218, 234, 117, 203, 29, 232,
    144, 238, 22, 150, 201, 117, 62, 207, 164, 13, 137, 245, 127, 67, 247, 28,
    155, 43, 203, 107, 233, 53, 143, 46},
  {242, 93, 169, 50, 144, 210, 39, 118, 202, 188, 201, 189, 143, 108, 196, 37,
    185, 112, 134, 230, 245, 63, 197, 190, 250, 106, 185, 221, 175, 64, 114, 71,
    161, 44, 147, 6, 27, 218, 51, 63, 87, 10, 40, 130, 188, 17, 163, 31,
    176, 170, 4, 107, 232, 7, 94, 166, 224, 124, 86, 47, 11, 204},
  {220, 228, 173, 89, 251, 149, 159, 56, 89, 33, 147, 244, 154, 36, 73, 127,
    213, 136, 248, 180, 234, 197, 158, 177, 68, 122, 93, 213, 15, 160, 227, 236,
    66, 139, 153, 185, 202, 167, 179, 25, 220, 232, 96, 210, 231, 136, 223, 239,
    181, 241, 59, 52, 172, 25, 49, 232, 211, 189, 64, 54, 108, 153, 132, 63,
    96, 103, 82, 186}};

const int MODULO_VALUE = 0x12D;

static int LOG[256], ALOG[256];

@implementation ZXDataMatrixErrorCorrection

+ (void)initialize {
  //Create log and antilog table
  int p = 1;
  for (int i = 0; i < 255; i++) {
    ALOG[i] = p;
    LOG[p] = i;
    p <<= 1;
    if (p >= 256) {
      p ^= MODULO_VALUE;
    }
  }
}

+ (NSString *)encodeECC200:(NSString *)codewords symbolInfo:(ZXSymbolInfo *)symbolInfo {
  if (codewords.length != symbolInfo.dataCapacity) {
    [NSException raise:NSInvalidArgumentException format:@"The number of codewords does not match the selected symbol"];
  }
  NSUInteger capacity = symbolInfo.dataCapacity + symbolInfo.errorCodewords;
  NSMutableString *sb = [NSMutableString stringWithCapacity:capacity];
  [sb appendString:codewords];
  int blockCount = symbolInfo.interleavedBlockCount;
  if (blockCount == 1) {
    NSString *ecc = [self createECCBlock:codewords numECWords:symbolInfo.errorCodewords];
    [sb appendString:ecc];
  } else {
    if (sb.length > capacity) {
      [sb deleteCharactersInRange:NSMakeRange(capacity, sb.length - capacity)];
    }
    int dataSizes[blockCount];
    int errorSizes[blockCount];
    int startPos[blockCount];
    for (int i = 0; i < blockCount; i++) {
      dataSizes[i] = [symbolInfo dataLengthForInterleavedBlock:i + 1];
      errorSizes[i] = [symbolInfo errorLengthForInterleavedBlock:i + 1];
      startPos[i] = 0;
      if (i > 0) {
        startPos[i] = startPos[i - 1] + dataSizes[i];
      }
    }
    for (int block = 0; block < blockCount; block++) {
      NSMutableString *temp = [NSMutableString stringWithCapacity:dataSizes[block]];
      for (int d = block; d < symbolInfo.dataCapacity; d += blockCount) {
        [temp appendFormat:@"%c", [codewords characterAtIndex:d]];
      }
      NSString *ecc = [self createECCBlock:temp numECWords:errorSizes[block]];
      int pos = 0;
      for (int e = block; e < errorSizes[block] * blockCount; e += blockCount) {
        [sb replaceCharactersInRange:NSMakeRange(symbolInfo.dataCapacity + e, 1) withString:[ecc substringWithRange:NSMakeRange(pos++, 1)]];
      }
    }
  }
  return [NSString stringWithString:sb];
}

+ (NSString *)createECCBlock:(NSString *)codewords numECWords:(int)numECWords {
  return [self createECCBlock:codewords start:0 len:(int)codewords.length numECWords:numECWords];
}

+ (NSString *)createECCBlock:(NSString *)codewords start:(int)start len:(int)len numECWords:(int)numECWords {
  int table = -1;
  for (int i = 0; i < FACTOR_SETS_LEN; i++) {
    if (FACTOR_SETS[i] == numECWords) {
      table = i;
      break;
    }
  }
  if (table < 0) {
    [NSException raise:NSInvalidArgumentException format:@"Illegal number of error correction codewords specified: %d", numECWords];
  }
  int *poly = (int *)FACTORS[table];
  unichar ecc[numECWords];
  memset(ecc, 0, numECWords * sizeof(unichar));
  for (int i = start; i < start + len; i++) {
    int m = ecc[numECWords - 1] ^ [codewords characterAtIndex:i];
    for (int k = numECWords - 1; k > 0; k--) {
      if (m != 0 && poly[k] != 0) {
        ecc[k] = (unichar) (ecc[k - 1] ^ ALOG[(LOG[m] + LOG[poly[k]]) % 255]);
      } else {
        ecc[k] = ecc[k - 1];
      }
    }
    if (m != 0 && poly[0] != 0) {
      ecc[0] = (unichar) ALOG[(LOG[m] + LOG[poly[0]]) % 255];
    } else {
      ecc[0] = 0;
    }
  }
  unichar eccReversed[numECWords];
  for (int i = 0; i < numECWords; i++) {
    eccReversed[i] = ecc[numECWords - i - 1];
  }
  return [NSString stringWithCharacters:eccReversed length:numECWords];
}

@end