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author | Tae-Young Chung <ty83.chung@samsung.com> | 2015-08-02 14:51:58 +0900 |
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committer | Tae-Young Chung <ty83.chung@samsung.com> | 2015-08-02 14:52:41 +0900 |
commit | 6b95e4f11a5ac5c9fbc89f9d0982787ddc24f929 (patch) | |
tree | 7f9464bdc97f155bd7910d9c21c6221feaf95354 /backend/reedsol.c | |
parent | b58273ff2547cde2ab6edcf2fca0530726f3efcc (diff) | |
download | libzint-6b95e4f11a5ac5c9fbc89f9d0982787ddc24f929.tar.gz libzint-6b95e4f11a5ac5c9fbc89f9d0982787ddc24f929.tar.bz2 libzint-6b95e4f11a5ac5c9fbc89f9d0982787ddc24f929.zip |
Add Zint Barcode Generator
Change-Id: I5fe674ec5ee8ba7249edd988822990974e01da06
Signed-off-by: Tae-Young Chung <ty83.chung@samsung.com>
Diffstat (limited to 'backend/reedsol.c')
-rw-r--r-- | backend/reedsol.c | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/backend/reedsol.c b/backend/reedsol.c new file mode 100644 index 0000000..ef9e402 --- /dev/null +++ b/backend/reedsol.c @@ -0,0 +1,171 @@ +/** + + This is a simple Reed-Solomon encoder + (C) Cliff Hones 2004 + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + 1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + 2. Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + 3. Neither the name of the project nor the names of its contributors + may be used to endorse or promote products derived from this software + without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND + ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE + FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + SUCH DAMAGE. +*/ + +// It is not written with high efficiency in mind, so is probably +// not suitable for real-time encoding. The aim was to keep it +// simple, general and clear. +// +// <Some notes on the theory and implementation need to be added here> + +// Usage: +// First call rs_init_gf(poly) to set up the Galois Field parameters. +// Then call rs_init_code(size, index) to set the encoding size +// Then call rs_encode(datasize, data, out) to encode the data. +// +// These can be called repeatedly as required - but note that +// rs_init_code must be called following any rs_init_gf call. +// +// If the parameters are fixed, some of the statics below can be +// replaced with constants in the obvious way, and additionally +// malloc/free can be avoided by using static arrays of a suitable +// size. + +#include <stdio.h> // only needed for debug (main) +#include <stdlib.h> // only needed for malloc/free +#include "reedsol.h" +static int gfpoly; +static int symsize; // in bits +static int logmod; // 2**symsize - 1 +static int rlen; + +static int *logt = NULL, *alog = NULL, *rspoly = NULL; + +// rs_init_gf(poly) initialises the parameters for the Galois Field. +// The symbol size is determined from the highest bit set in poly +// This implementation will support sizes up to 30 bits (though that +// will result in very large log/antilog tables) - bit sizes of +// 8 or 4 are typical +// +// The poly is the bit pattern representing the GF characteristic +// polynomial. e.g. for ECC200 (8-bit symbols) the polynomial is +// a**8 + a**5 + a**3 + a**2 + 1, which translates to 0x12d. + +void rs_init_gf(int poly) +{ + int m, b, p, v; + + // Find the top bit, and hence the symbol size + for (b = 1, m = 0; b <= poly; b <<= 1) + m++; + b >>= 1; + m--; + gfpoly = poly; + symsize = m; + + // Calculate the log/alog tables + logmod = (1 << m) - 1; + logt = (int *)malloc(sizeof(int) * (logmod + 1)); + alog = (int *)malloc(sizeof(int) * logmod); + + for (p = 1, v = 0; v < logmod; v++) { + alog[v] = p; + logt[p] = v; + p <<= 1; + if (p & b) + p ^= poly; + } +} + +// rs_init_code(nsym, index) initialises the Reed-Solomon encoder +// nsym is the number of symbols to be generated (to be appended +// to the input data). index is usually 1 - it is the index of +// the constant in the first term (i) of the RS generator polynomial: +// (x + 2**i)*(x + 2**(i+1))*... [nsym terms] +// For ECC200, index is 1. + +void rs_init_code(int nsym, int index) +{ + int i, k; + + rspoly = (int *)malloc(sizeof(int) * (nsym + 1)); + + rlen = nsym; + + rspoly[0] = 1; + for (i = 1; i <= nsym; i++) { + rspoly[i] = 1; + for (k = i - 1; k > 0; k--) { + if (rspoly[k]) + rspoly[k] = alog[(logt[rspoly[k]] + index) % logmod]; + rspoly[k] ^= rspoly[k - 1]; + } + rspoly[0] = alog[(logt[rspoly[0]] + index) % logmod]; + index++; + } +} + +void rs_encode(int len, unsigned char *data, unsigned char *res) +{ + int i, k, m; + for (i = 0; i < rlen; i++) + res[i] = 0; + for (i = 0; i < len; i++) { + m = res[rlen - 1] ^ data[i]; + for (k = rlen - 1; k > 0; k--) { + if (m && rspoly[k]) + res[k] = res[k - 1] ^ alog[(logt[m] + logt[rspoly[k]]) % logmod]; + else + res[k] = res[k - 1]; + } + if (m && rspoly[0]) + res[0] = alog[(logt[m] + logt[rspoly[0]]) % logmod]; + else + res[0] = 0; + } +} + +void rs_encode_long(int len, unsigned int *data, unsigned int *res) +{ /* The same as above but for larger bitlengths - Aztec code compatible */ + int i, k, m; + for (i = 0; i < rlen; i++) + res[i] = 0; + for (i = 0; i < len; i++) { + m = res[rlen - 1] ^ data[i]; + for (k = rlen - 1; k > 0; k--) { + if (m && rspoly[k]) + res[k] = res[k - 1] ^ alog[(logt[m] + logt[rspoly[k]]) % logmod]; + else + res[k] = res[k - 1]; + } + if (m && rspoly[0]) + res[0] = alog[(logt[m] + logt[rspoly[0]]) % logmod]; + else + res[0] = 0; + } +} + +void rs_free(void) +{ /* Free memory */ + free(logt); + free(alog); + free(rspoly); + rspoly = NULL; +} |