ham84.c

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/*

$Log$
Revision 1.15 2004/06/26 03:50:14 markster
Merge source cleanups (bug #1911)

Revision 1.14 2003/02/12 13:59:15 matteo
mer feb 12 14:56:57 CET 2003

Revision 1.1.1.1 2003/02/12 13:59:15 matteo
mer feb 12 14:56:57 CET 2003

Revision 1.2 2000/01/05 08:20:39 markster
Some OSS fixes and a few lpc changes to make it actually work

 * Revision 1.1 1996/08/19 22:32:07 jaf
 * Initial revision
 *

*/

/* -- translated by f2c (version 19951025).
 You must link the resulting object file with the libraries:
 -lf2c -lm (in that order)
*/

#include "f2c.h"

#ifdef P_R_O_T_O_T_Y_P_E_S
extern int ham84_(integer *input, integer *output, integer *errcnt);
#endif

/* ***************************************************************** */

/* HAM84 Version 45G */

/* $Log$
 * Revision 1.15 2004/06/26 03:50:14 markster
 * Merge source cleanups (bug #1911)
 *
 * Revision 1.14 2003/02/12 13:59:15 matteo
 * mer feb 12 14:56:57 CET 2003
 *
 * Revision 1.1.1.1 2003/02/12 13:59:15 matteo
 * mer feb 12 14:56:57 CET 2003
 *
 * Revision 1.2 2000/01/05 08:20:39 markster
 * Some OSS fixes and a few lpc changes to make it actually work
 *
 * Revision 1.1 1996/08/19 22:32:07 jaf
 * Initial revision
 * */
/* Revision 1.3 1996/03/21 15:26:00 jaf */
/* Put comment header in standard form. */

/* Revision 1.2 1996/03/13 22:00:13 jaf */
/* Comments added explaining that none of the local variables of this */
/* subroutine need to be saved from one invocation to the next. */

/* Revision 1.1 1996/02/07 14:47:04 jaf */
/* Initial revision */


/* ***************************************************************** */

/* Hamming 8,4 Decoder - can correct 1 out of seven bits */
/* and can detect up to two errors. */

/* Input: */
/* INPUT - Seven bit data word, 4 bits parameter and */
/* 4 bits parity information */
/* Input/Output: */
/* ERRCNT - Sums errors detected by Hamming code */
/* Output: */
/* OUTPUT - 4 corrected parameter bits */

/* This subroutine is entered with an eight bit word in INPUT. The 8th */
/* bit is parity and is stripped off. The remaining 7 bits address the */
/* hamming 8,4 table and the output OUTPUT from the table gives the 4 */
/* bits of corrected data. If bit 4 is set, no error was detected. */
/* ERRCNT is the number of errors counted. */

/* This subroutine has no local state. */

/* Subroutine */ int ham84_(integer *input, integer *output, integer *errcnt)
{
 /* Initialized data */

 static integer dactab[128] = { 16,0,0,3,0,5,14,7,0,9,14,11,14,13,30,14,0,
 9,2,7,4,7,7,23,9,25,10,9,12,9,14,7,0,5,2,11,5,21,6,5,8,11,11,27,
 12,5,14,11,2,1,18,2,12,5,2,7,12,9,2,11,28,12,12,15,0,3,3,19,4,13,
 6,3,8,13,10,3,13,29,14,13,4,1,10,3,20,4,4,7,10,9,26,10,4,13,10,15,
 8,1,6,3,6,5,22,6,24,8,8,11,8,13,6,15,1,17,2,1,4,1,6,15,8,1,10,15,
 12,15,15,31 };

 integer i__, j, parity;

/* Arguments */
/* Parameters/constants */
/* Local variables that need not be saved */
/* Determine parity of input word */
 parity = *input & 255;
 parity ^= parity / 16;
 parity ^= parity / 4;
 parity ^= parity / 2;
 parity &= 1;
 i__ = dactab[*input & 127];
 *output = i__ & 15;
 j = i__ & 16;
 if (j != 0) {
/* No errors detected in seven bits */
 if (parity != 0) {
 ++(*errcnt);
 }
 } else {
/* One or two errors detected */
 ++(*errcnt);
 if (parity == 0) {
/* Two errors detected */
 ++(*errcnt);
 *output = -1;
 }
 }
 return 0;
} /* ham84_ */