ref: 2024869a595118d686682b38386c594c717ea5bd
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_ */