150 lines
3.8 KiB
C
150 lines
3.8 KiB
C
/*
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* qrencode - QR Code encoder
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*
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* Reed solomon error correction code encoder specialized for QR code.
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* This code is rewritten by Kentaro Fukuchi, referring to the FEC library
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* developed by Phil Karn (KA9Q).
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*
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* Copyright (C) 2002, 2003, 2004, 2006 Phil Karn, KA9Q
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* Copyright (C) 2014-2017 Kentaro Fukuchi <kentaro@fukuchi.org>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#if HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <stdlib.h>
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#include <string.h>
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#if HAVE_LIBPTHREAD
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#include <pthread.h>
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#endif
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#include "rsecc.h"
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#if HAVE_LIBPTHREAD
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static pthread_mutex_t RSECC_mutex = PTHREAD_MUTEX_INITIALIZER;
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#endif
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static int initialized = 0;
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#define SYMBOL_SIZE (8)
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#define symbols ((1U << SYMBOL_SIZE) - 1)
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static const unsigned int proot = 0x11d; /* stands for x^8+x^4+x^3+x^2+1 (see pp.37 of JIS X0510:2004) */
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/* min/max codeword length of ECC, calculated from the specification. */
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#define min_length (2)
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#define max_length (30)
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#define max_generatorSize (max_length)
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static unsigned char alpha[symbols + 1];
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static unsigned char aindex[symbols + 1];
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static unsigned char generator[max_length - min_length + 1][max_generatorSize + 1];
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static unsigned char generatorInitialized[max_length - min_length + 1];
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static void RSECC_initLookupTable(void)
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{
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unsigned int i, b;
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alpha[symbols] = 0;
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aindex[0] = symbols;
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b = 1;
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for(i = 0; i < symbols; i++) {
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alpha[i] = b;
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aindex[b] = i;
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b <<= 1;
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if(b & (symbols + 1)) {
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b ^= proot;
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}
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b &= symbols;
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}
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}
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static void RSECC_init(void)
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{
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RSECC_initLookupTable();
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memset(generatorInitialized, 0, (max_length - min_length + 1));
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initialized = 1;
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}
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static void generator_init(size_t length)
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{
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size_t i, j;
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int g[max_generatorSize + 1];
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g[0] = 1;
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for(i = 0; i < length; i++) {
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g[i + 1] = 1;
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/* Because g[0] never be zero, skipped some conditional checks. */
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for(j = i; j > 0; j--) {
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g[j] = g[j - 1] ^ alpha[(aindex[g[j]] + i) % symbols];
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}
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g[0] = alpha[(aindex[g[0]] + i) % symbols];
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}
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for(i = 0; i <= length; i++) {
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generator[length - min_length][i] = aindex[g[i]];
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}
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generatorInitialized[length - min_length] = 1;
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}
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int RSECC_encode(size_t data_length, size_t ecc_length, const unsigned char *data, unsigned char *ecc)
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{
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size_t i, j;
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unsigned char feedback;
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unsigned char *gen;
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#if HAVE_LIBPTHREAD
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pthread_mutex_lock(&RSECC_mutex);
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#endif
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if(!initialized) {
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RSECC_init();
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}
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#if HAVE_LIBPTHREAD
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pthread_mutex_unlock(&RSECC_mutex);
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#endif
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if(ecc_length > max_length) return -1;
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memset(ecc, 0, ecc_length);
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#if HAVE_LIBPTHREAD
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pthread_mutex_lock(&RSECC_mutex);
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#endif
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if(!generatorInitialized[ecc_length - min_length]) generator_init(ecc_length);
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#if HAVE_LIBPTHREAD
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pthread_mutex_unlock(&RSECC_mutex);
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#endif
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gen = generator[ecc_length - min_length];
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for(i = 0; i < data_length; i++) {
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feedback = aindex[data[i] ^ ecc[0]];
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if(feedback != symbols) {
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for(j = 1; j < ecc_length; j++) {
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ecc[j] ^= alpha[(unsigned int)(feedback + gen[ecc_length - j]) % symbols];
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}
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}
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memmove(&ecc[0], &ecc[1], ecc_length - 1);
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if(feedback != symbols) {
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ecc[ecc_length - 1] = alpha[(unsigned int)(feedback + gen[0]) % symbols];
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} else {
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ecc[ecc_length - 1] = 0;
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}
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}
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return 0;
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}
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