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PARITY.C
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1997-07-05
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/* +++Date last modified: 05-Jul-1997 */
/*
** PARITY.C - Computes even or odd parity for various integral types
**
** public domain demo by Bob Stout
*/
#include "parity.h"
unsigned parity32(unsigned long x, Parity_T even)
{
x = x ^ (x >> 16);
x = x ^ (x >> 8);
x = x ^ (x >> 4);
x = x ^ (x >> 2);
x = x ^ (x >> 1);
return ((unsigned)(x & 1)) ^ even;
}
unsigned parity16(unsigned short x, Parity_T even)
{
x = x ^ (x >> 8);
x = x ^ (x >> 4);
x = x ^ (x >> 2);
x = x ^ (x >> 1);
return ((unsigned)(x & 1)) ^ even;
}
unsigned parity8(unsigned char x, Parity_T even)
{
x = x ^ (x >> 4);
x = x ^ (x >> 2);
x = x ^ (x >> 1);
return ((unsigned)(x & 1)) ^ even;
}
unsigned parity64(void *x, Parity_T even)
{
union longlong *val64 = (union longlong *)x;
return (parity32(val64->lo, even) ^ parity32(val64->hi, even));
}
#ifdef TEST
#include <stdio.h>
#include <stdlib.h>
main(int argc, char *argv[])
{
while (--argc)
{
unsigned long n = strtoul(*(++argv), NULL, 10);
printf("Even parity of %ld = %d\n", n, parity32(n, Even_));
printf("Odd parity of %ld = %d\n\n", n, parity32(n, Odd_));
}
}
#endif