-/**
+/**
*
* This is a simple Reed-Solomon encoder
* (C) Cliff Hones 2004
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
- */
-
+ */
// It is not written with high efficiency in mind, so is probably
// not suitable for real-time encoding. The aim was to keep it
// 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 <stdio.h> // only needed for debug (main)
+#include <stdlib.h> // only needed for malloc/free
static int gfpoly;
-static int symsize; // in bits
-static int logmod; // 2**symsize - 1
+static int symsize; // in bits
+static int logmod; // 2**symsize - 1
static int rlen;
-static int *log = NULL,
- *alog = NULL,
- *rspoly = NULL;
+static int *log = 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
// 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)
+void rs_init_gf(int poly)
{
- int m,
- b,
- p,
- v;
-
- // Return storage from previous setup
- if (log)
- {
- free (log);
- free (alog);
- free (rspoly);
- rspoly = NULL;
- }
- // 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;
- log = (int *) malloc (sizeof (int) * (logmod + 1));
- alog = (int *) malloc (sizeof (int) * logmod);
-
- for (p = 1, v = 0; v < logmod; v++)
- {
- alog[v] = p;
- log[p] = v;
- p <<= 1;
- if (p & b)
- p ^= poly;
- }
+ int m, b, p, v;
+
+ // Return storage from previous setup
+ if (log) {
+ free(log);
+ free(alog);
+ free(rspoly);
+ rspoly = NULL;
+ }
+ // 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;
+ log = (int *)malloc(sizeof(int) * (logmod + 1));
+ alog = (int *)malloc(sizeof(int) * logmod);
+
+ for (p = 1, v = 0; v < logmod; v++) {
+ alog[v] = p;
+ log[p] = v;
+ p <<= 1;
+ if (p & b)
+ p ^= poly;
+ }
}
// rs_init_code(nsym, index) initialises the Reed-Solomon encoder
// (x + 2**i)*(x + 2**(i+1))*... [nsym terms]
// For ECC200, index is 1.
-void
-rs_init_code (int nsym, int index)
+void rs_init_code(int nsym, int index)
{
- int i,
- k;
-
- if (rspoly)
- free (rspoly);
- 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[(log[rspoly[k]] + index) % logmod];
- rspoly[k] ^= rspoly[k - 1];
- }
- rspoly[0] = alog[(log[rspoly[0]] + index) % logmod];
- index++;
- }
+ int i, k;
+
+ if (rspoly)
+ free(rspoly);
+ 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[(log[rspoly[k]] + index) % logmod];
+ rspoly[k] ^= rspoly[k - 1];
+ }
+ rspoly[0] = alog[(log[rspoly[0]] + index) % logmod];
+ index++;
+ }
}
// Note that the following uses byte arrays, so is only suitable for
// symbol sizes up to 8 bits. Just change the data type of data and res
// to unsigned int * for larger symbols.
-void
-rs_encode (int len, unsigned char *data, unsigned char *res)
+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[(log[m] + log[rspoly[k]]) % logmod];
- else
- res[k] = res[k - 1];
- }
- if (m && rspoly[0])
- res[0] = alog[(log[m] + log[rspoly[0]]) % logmod];
- else
- res[0] = 0;
- }
+ 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[(log[m] +
+ log[rspoly[k]]) % logmod];
+ else
+ res[k] = res[k - 1];
+ }
+ if (m && rspoly[0])
+ res[0] = alog[(log[m] + log[rspoly[0]]) % logmod];
+ else
+ res[0] = 0;
+ }
}
#ifndef LIB
// The following tests the routines with the ISO/IEC 16022 Annexe R data
-int
-main (void)
+int reedsol_main(void)
{
- register int i;
+ register int i;
- unsigned char data[9] = { 142, 164, 186 };
- unsigned char out[5];
+ unsigned char data[9] = { 142, 164, 186 };
+ unsigned char out[5];
- rs_init_gf (0x12d);
- rs_init_code (5, 1);
+ rs_init_gf(0x12d);
+ rs_init_code(5, 1);
- rs_encode (3, data, out);
+ rs_encode(3, data, out);
- printf ("Result of Annexe R encoding:\n");
- for (i = 4; i >= 0; i--)
- printf (" %d\n", out[i]);
+ printf("Result of Annexe R encoding:\n");
+ for (i = 4; i >= 0; i--)
+ printf(" %d\n", out[i]);
- return 0;
+ return 0;
}
#endif
projects / iec16022 / blobdiff