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swap.c
34 lines (34 loc) · 1.37 KB
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swap.c
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/*
* MINEOS version 1.0 by Guy Masters, John Woodhouse, and Freeman Gilbert
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
***************************************************************************
*
* Byte swap in place an array b of n of elements each one N bytes long.
* A good compiler should unroll the inner loops. Letting the compiler do it
* gives us portability. Note that we might want to isolate the
* cases N = 2, 4, 8 (and 16 for long double and perhaps long long)
*
*/
#define SWAP2(a, b) { (a) ^= (b); (b) ^= (a); (a) ^= (b); }
void swapn(unsigned char *b, int N, int n)
{
int i, j;
for (i = 0; i < (n)*(N); i += N)
for (j = 0; j < N/2; j ++)
SWAP2(b[i + j], b[i + N - j - 1]);
return;
}