| /* |
| * qrencode - QR Code encoder |
| * |
| * Reed solomon encoder. This code is taken from Phil Karn's libfec then |
| * editted and packed into a pair of .c and .h files. |
| * |
| * Copyright (C) 2002, 2003, 2004, 2006 Phil Karn, KA9Q |
| * (libfec is released under the GNU Lesser General Public License.) |
| * |
| * Copyright (C) 2006-2011 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 "rscode.h" |
| |
| /* Stuff specific to the 8-bit symbol version of the general purpose RS codecs |
| * |
| */ |
| typedef unsigned char data_t; |
| |
| |
| /** |
| * Reed-Solomon codec control block |
| */ |
| struct _RS { |
| int mm; /* Bits per symbol */ |
| int nn; /* Symbols per block (= (1<<mm)-1) */ |
| data_t *alpha_to; /* log lookup table */ |
| data_t *index_of; /* Antilog lookup table */ |
| data_t *genpoly; /* Generator polynomial */ |
| int nroots; /* Number of generator roots = number of parity symbols */ |
| int fcr; /* First consecutive root, index form */ |
| int prim; /* Primitive element, index form */ |
| int iprim; /* prim-th root of 1, index form */ |
| int pad; /* Padding bytes in shortened block */ |
| int gfpoly; |
| struct _RS *next; |
| }; |
| |
| static RS *rslist = NULL; |
| #ifdef HAVE_LIBPTHREAD |
| static pthread_mutex_t rslist_mutex = PTHREAD_MUTEX_INITIALIZER; |
| #endif |
| |
| static int modnn(RS *rs, int x){ |
| while (x >= rs->nn) { |
| x -= rs->nn; |
| x = (x >> rs->mm) + (x & rs->nn); |
| } |
| return x; |
| } |
| |
| |
| #define MODNN(x) modnn(rs,x) |
| |
| #define MM (rs->mm) |
| #define NN (rs->nn) |
| #define ALPHA_TO (rs->alpha_to) |
| #define INDEX_OF (rs->index_of) |
| #define GENPOLY (rs->genpoly) |
| #define NROOTS (rs->nroots) |
| #define FCR (rs->fcr) |
| #define PRIM (rs->prim) |
| #define IPRIM (rs->iprim) |
| #define PAD (rs->pad) |
| #define A0 (NN) |
| |
| |
| /* Initialize a Reed-Solomon codec |
| * symsize = symbol size, bits |
| * gfpoly = Field generator polynomial coefficients |
| * fcr = first root of RS code generator polynomial, index form |
| * prim = primitive element to generate polynomial roots |
| * nroots = RS code generator polynomial degree (number of roots) |
| * pad = padding bytes at front of shortened block |
| */ |
| static RS *init_rs_char(int symsize, int gfpoly, int fcr, int prim, int nroots, int pad) |
| { |
| RS *rs; |
| |
| |
| /* Common code for intializing a Reed-Solomon control block (char or int symbols) |
| * Copyright 2004 Phil Karn, KA9Q |
| * May be used under the terms of the GNU Lesser General Public License (LGPL) |
| */ |
| //#undef NULL |
| //#define NULL ((void *)0) |
| |
| int i, j, sr,root,iprim; |
| |
| rs = NULL; |
| /* Check parameter ranges */ |
| if(symsize < 0 || symsize > (int)(8*sizeof(data_t))){ |
| goto done; |
| } |
| |
| if(fcr < 0 || fcr >= (1<<symsize)) |
| goto done; |
| if(prim <= 0 || prim >= (1<<symsize)) |
| goto done; |
| if(nroots < 0 || nroots >= (1<<symsize)) |
| goto done; /* Can't have more roots than symbol values! */ |
| if(pad < 0 || pad >= ((1<<symsize) -1 - nroots)) |
| goto done; /* Too much padding */ |
| |
| rs = (RS *)calloc(1,sizeof(RS)); |
| if(rs == NULL) |
| goto done; |
| |
| rs->mm = symsize; |
| rs->nn = (1<<symsize)-1; |
| rs->pad = pad; |
| |
| rs->alpha_to = (data_t *)malloc(sizeof(data_t)*(rs->nn+1)); |
| if(rs->alpha_to == NULL){ |
| free(rs); |
| rs = NULL; |
| goto done; |
| } |
| rs->index_of = (data_t *)malloc(sizeof(data_t)*(rs->nn+1)); |
| if(rs->index_of == NULL){ |
| free(rs->alpha_to); |
| free(rs); |
| rs = NULL; |
| goto done; |
| } |
| |
| /* Generate Galois field lookup tables */ |
| rs->index_of[0] = A0; /* log(zero) = -inf */ |
| rs->alpha_to[A0] = 0; /* alpha**-inf = 0 */ |
| sr = 1; |
| for(i=0;i<rs->nn;i++){ |
| rs->index_of[sr] = i; |
| rs->alpha_to[i] = sr; |
| sr <<= 1; |
| if(sr & (1<<symsize)) |
| sr ^= gfpoly; |
| sr &= rs->nn; |
| } |
| if(sr != 1){ |
| /* field generator polynomial is not primitive! */ |
| free(rs->alpha_to); |
| free(rs->index_of); |
| free(rs); |
| rs = NULL; |
| goto done; |
| } |
| |
| /* Form RS code generator polynomial from its roots */ |
| rs->genpoly = (data_t *)malloc(sizeof(data_t)*(nroots+1)); |
| if(rs->genpoly == NULL){ |
| free(rs->alpha_to); |
| free(rs->index_of); |
| free(rs); |
| rs = NULL; |
| goto done; |
| } |
| rs->fcr = fcr; |
| rs->prim = prim; |
| rs->nroots = nroots; |
| rs->gfpoly = gfpoly; |
| |
| /* Find prim-th root of 1, used in decoding */ |
| for(iprim=1;(iprim % prim) != 0;iprim += rs->nn) |
| ; |
| rs->iprim = iprim / prim; |
| |
| rs->genpoly[0] = 1; |
| for (i = 0,root=fcr*prim; i < nroots; i++,root += prim) { |
| rs->genpoly[i+1] = 1; |
| |
| /* Multiply rs->genpoly[] by @**(root + x) */ |
| for (j = i; j > 0; j--){ |
| if (rs->genpoly[j] != 0) |
| rs->genpoly[j] = rs->genpoly[j-1] ^ rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[j]] + root)]; |
| else |
| rs->genpoly[j] = rs->genpoly[j-1]; |
| } |
| /* rs->genpoly[0] can never be zero */ |
| rs->genpoly[0] = rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[0]] + root)]; |
| } |
| /* convert rs->genpoly[] to index form for quicker encoding */ |
| for (i = 0; i <= nroots; i++) |
| rs->genpoly[i] = rs->index_of[rs->genpoly[i]]; |
| done:; |
| |
| return rs; |
| } |
| |
| RS *init_rs(int symsize, int gfpoly, int fcr, int prim, int nroots, int pad) |
| { |
| RS *rs; |
| |
| #ifdef HAVE_LIBPTHREAD |
| pthread_mutex_lock(&rslist_mutex); |
| #endif |
| for(rs = rslist; rs != NULL; rs = rs->next) { |
| if(rs->pad != pad) continue; |
| if(rs->nroots != nroots) continue; |
| if(rs->mm != symsize) continue; |
| if(rs->gfpoly != gfpoly) continue; |
| if(rs->fcr != fcr) continue; |
| if(rs->prim != prim) continue; |
| |
| goto DONE; |
| } |
| |
| rs = init_rs_char(symsize, gfpoly, fcr, prim, nroots, pad); |
| if(rs == NULL) goto DONE; |
| rs->next = rslist; |
| rslist = rs; |
| |
| DONE: |
| #ifdef HAVE_LIBPTHREAD |
| pthread_mutex_unlock(&rslist_mutex); |
| #endif |
| return rs; |
| } |
| |
| |
| void free_rs_char(RS *rs) |
| { |
| free(rs->alpha_to); |
| free(rs->index_of); |
| free(rs->genpoly); |
| free(rs); |
| } |
| |
| void free_rs_cache(void) |
| { |
| RS *rs, *next; |
| |
| #ifdef HAVE_LIBPTHREAD |
| pthread_mutex_lock(&rslist_mutex); |
| #endif |
| rs = rslist; |
| while(rs != NULL) { |
| next = rs->next; |
| free_rs_char(rs); |
| rs = next; |
| } |
| rslist = NULL; |
| #ifdef HAVE_LIBPTHREAD |
| pthread_mutex_unlock(&rslist_mutex); |
| #endif |
| } |
| |
| /* The guts of the Reed-Solomon encoder, meant to be #included |
| * into a function body with the following typedefs, macros and variables supplied |
| * according to the code parameters: |
| |
| * data_t - a typedef for the data symbol |
| * data_t data[] - array of NN-NROOTS-PAD and type data_t to be encoded |
| * data_t parity[] - an array of NROOTS and type data_t to be written with parity symbols |
| * NROOTS - the number of roots in the RS code generator polynomial, |
| * which is the same as the number of parity symbols in a block. |
| Integer variable or literal. |
| * |
| * NN - the total number of symbols in a RS block. Integer variable or literal. |
| * PAD - the number of pad symbols in a block. Integer variable or literal. |
| * ALPHA_TO - The address of an array of NN elements to convert Galois field |
| * elements in index (log) form to polynomial form. Read only. |
| * INDEX_OF - The address of an array of NN elements to convert Galois field |
| * elements in polynomial form to index (log) form. Read only. |
| * MODNN - a function to reduce its argument modulo NN. May be inline or a macro. |
| * GENPOLY - an array of NROOTS+1 elements containing the generator polynomial in index form |
| |
| * The memset() and memmove() functions are used. The appropriate header |
| * file declaring these functions (usually <string.h>) must be included by the calling |
| * program. |
| |
| * Copyright 2004, Phil Karn, KA9Q |
| * May be used under the terms of the GNU Lesser General Public License (LGPL) |
| */ |
| |
| #undef A0 |
| #define A0 (NN) /* Special reserved value encoding zero in index form */ |
| |
| void encode_rs_char(RS *rs, const data_t *data, data_t *parity) |
| { |
| int i, j; |
| data_t feedback; |
| |
| memset(parity,0,NROOTS*sizeof(data_t)); |
| |
| for(i=0;i<NN-NROOTS-PAD;i++){ |
| feedback = INDEX_OF[data[i] ^ parity[0]]; |
| if(feedback != A0){ /* feedback term is non-zero */ |
| #ifdef UNNORMALIZED |
| /* This line is unnecessary when GENPOLY[NROOTS] is unity, as it must |
| * always be for the polynomials constructed by init_rs() |
| */ |
| feedback = MODNN(NN - GENPOLY[NROOTS] + feedback); |
| #endif |
| for(j=1;j<NROOTS;j++) |
| parity[j] ^= ALPHA_TO[MODNN(feedback + GENPOLY[NROOTS-j])]; |
| } |
| /* Shift */ |
| memmove(&parity[0],&parity[1],sizeof(data_t)*(NROOTS-1)); |
| if(feedback != A0) |
| parity[NROOTS-1] = ALPHA_TO[MODNN(feedback + GENPOLY[0])]; |
| else |
| parity[NROOTS-1] = 0; |
| } |
| } |