kc3-lang/libqrencode/rsecc.c

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• Author : Sebastian Buchwald
  Date : 2015-08-17 17:24:23
  Hash : d6e262a7
  Message : Make functions static.

• rsecc.c

• /*
   * qrencode - QR Code encoder
   *
   * Reed solomon error correction code encoder specialized for QR code.
   * This code is rewritten by Kentaro Fukuchi, referring to the FEC library
   * developed by Phil Karn (KA9Q).
   *
   * Copyright (C) 2002, 2003, 2004, 2006 Phil Karn, KA9Q
   * Copyright (C) 2014 Kentaro Fukuchi <kentaro@fukuchi.org>
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #if HAVE_CONFIG_H
  # include "config.h"
  #endif
  #include <stdlib.h>
  #include <string.h>
  #ifdef HAVE_LIBPTHREAD
  #include <pthread.h>
  #endif
  
  #include "rsecc.h"
  
  #ifdef HAVE_LIBPTHREAD
  static pthread_mutex_t RSECC_mutex = PTHREAD_MUTEX_INITIALIZER;
  #endif
  
  static int initialized = 0;
  
  #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];
  static unsigned char generator[max_length - min_length + 1][max_generatorSize + 1];
  static unsigned char generatorInitialized[max_length - min_length + 1];
  
  static void RSECC_initLookupTable(void)
  {
  	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;
  	}
  }
  
  static void RSECC_init(void)
  {
  	RSECC_initLookupTable();
  	memset(generatorInitialized, 0, (max_length - min_length + 1));
  	initialized = 1;
  }
  
  static void generator_init(int length)
  {
  	int i, j;
  	int g[max_generatorSize + 1];
  
  	g[0] = 1;
  	for(i = 0; i < length; i++) {
  		g[i + 1] = 1;
  		/* Because g[0] never be zero, skipped some conditional checks. */
  		for(j = i; j > 0; j--) {
  			g[j] = g[j - 1] ^  alpha[(aindex[g[j]] + i) % symbols];
  		}
  		g[0] = alpha[(aindex[g[0]] + i) % symbols];
  	}
  
  	for(i = 0; i <= length; i++) {
  		generator[length - min_length][i] = aindex[g[i]];
  	}
  
  	generatorInitialized[length - min_length] = 1;
  }
  
  int RSECC_encode(int data_length, int ecc_length, const unsigned char *data, unsigned char *ecc)
  {
  	int i, j;
  	unsigned char feedback;
  	unsigned char *gen;
  
  #ifdef HAVE_LIBPTHREAD
  	pthread_mutex_lock(&RSECC_mutex);
  #endif
  	if(!initialized) {
  		RSECC_init();
  	}
  #ifdef HAVE_LIBPTHREAD
  	pthread_mutex_unlock(&RSECC_mutex);
  #endif
  
  	if(ecc_length > max_length) return -1;
  
  	memset(ecc, 0, ecc_length);
  #ifdef HAVE_LIBPTHREAD
  	pthread_mutex_lock(&RSECC_mutex);
  #endif
  	if(!generatorInitialized[ecc_length - min_length]) generator_init(ecc_length);
  #ifdef HAVE_LIBPTHREAD
  	pthread_mutex_unlock(&RSECC_mutex);
  #endif
  	gen = generator[ecc_length - min_length];
  
  	for(i = 0; i < data_length; i++) {
  		feedback = aindex[data[i] ^ ecc[0]];
  		if(feedback != symbols) {
  			for(j = 1; j < ecc_length; j++) {
  				ecc[j] ^= alpha[(feedback + gen[ecc_length - j]) % symbols];
  			}
  		}
  		memmove(&ecc[0], &ecc[1], ecc_length - 1);
  		if(feedback != symbols) {
  			ecc[ecc_length - 1] = alpha[(feedback + gen[0]) % symbols];
  		} else {
  			ecc[ecc_length - 1] = 0;
  		}
  	}
  
  	return 0;
  }