116 lines
3.2 KiB
C
116 lines
3.2 KiB
C
/*
|
|
|
|
$Log: ham84.c,v $
|
|
Revision 1.1 2004/05/04 11:16:42 csoutheren
|
|
Initial version
|
|
|
|
Revision 1.1 2000/06/05 04:45:12 robertj
|
|
Added LPC-10 2400bps codec
|
|
|
|
* Revision 1.1 1996/08/19 22:32:07 jaf
|
|
* Initial revision
|
|
*
|
|
|
|
*/
|
|
|
|
#ifdef P_R_O_T_O_T_Y_P_E_S
|
|
extern int ham84_(integer *input, integer *output, integer *errcnt);
|
|
#endif
|
|
|
|
/* -- translated by f2c (version 19951025).
|
|
You must link the resulting object file with the libraries:
|
|
-lf2c -lm (in that order)
|
|
*/
|
|
|
|
#include "f2c.h"
|
|
|
|
/* ***************************************************************** */
|
|
|
|
/* HAM84 Version 45G */
|
|
|
|
/* $Log: ham84.c,v $
|
|
* Revision 1.1 2004/05/04 11:16:42 csoutheren
|
|
* Initial version
|
|
*
|
|
* Revision 1.1 2000/06/05 04:45:12 robertj
|
|
* Added LPC-10 2400bps codec
|
|
*
|
|
* 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_ */
|
|
|