kc3-lang/libqrencode/tests/rsecc_decoder.c

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• Hash : dd730546
  Author :
  Date : 2014-09-18T19:27:43
  

  Syndrome checker has been added.
  

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• tests/rsecc_decoder.c

• #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include "../qrspec.h"
  #include "rsecc_decoder.h"
  
  #define SYMBOL_SIZE (8)
  #define symbols ((1 << SYMBOL_SIZE) - 1)
  static const int proot = 0x11d; /* stands for x^8+x^4+x^3+x^2+1 (see pp.37 of JIS X0510:2004) */
  
  /* min/max codeword length of ECC, calculated from the specification. */
  #define min_length (2)
  #define max_length (30)
  #define max_generatorSize (max_length)
  
  static unsigned char alpha[symbols + 1];
  static unsigned char aindex[symbols + 1];
  
  void RSECC_decoder_init() {
  	int i, b;
  
  	alpha[symbols] = 0;
  	aindex[0] = symbols;
  
  	b = 1;
  	for(i = 0; i < symbols; i++) {
  		alpha[i] = b;
  		aindex[b] = i;
  		b <<= 1;
  		if(b & (symbols + 1)) {
  			b ^= proot;
  		}
  		b &= symbols;
  	}
  }
  
  int RSECC_decoder_checkSyndrome(int dl, unsigned char *data, int el, unsigned char *ecc)
  {
  	int i, j;
  	int s;
  
  	for(i=0; i<el; i++) {
  		s = data[0];
  		for(j=1; j<dl; j++) {
  			if(s == 0) {
  				s = data[j];
  			} else {
  				s = data[j] ^ alpha[(aindex[s] + i) % symbols];
  			}
  		}
  		for(j=0; j<el; j++) {
  			if(s == 0) {
  				s = ecc[j];
  			} else {
  				s = ecc[j] ^ alpha[(aindex[s] + i) % symbols];
  			}
  		}
  		if(s != 0) {
  			return -1;
  		}
  	}
  
  	return 0;
  }
  

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