ref: 42f8ff432b68d90bdd981394a582a86a528b6482
dir: /lpc10/ham84.c/
/*
* 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"
extern int ham84_(integer *input, integer *output, integer *errcnt);
/* ***************************************************************** */
/* HAM84 Version 45G */
/*
* 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_ */