Edit
kc3-lang/libqrencode/tests/rscode.c
Sebastian Buchwald
- tests/rscode.c
-
/* * 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> #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; }; static inline 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) { return init_rs_char(symsize, gfpoly, fcr, prim, nroots, pad); } void free_rs_char(RS *rs) { free(rs->alpha_to); free(rs->index_of); free(rs->genpoly); free(rs); } /* 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; } }