source: trunk/sys/dietlibc/ffs.c @ 1

Last change on this file since 1 was 1, checked in by alain, 5 years ago

First import

File size: 544 bytes
Line 
1#include <strings.h>
2
3int ffs(int i) {
4  int plus=0;
5  /* return index of rightmost bit set */
6  /* ffs(1) == 1, ffs(2) == 2, ffs(256) == 9, ffs(257)=1 */
7#if 0
8  if (sizeof(i)==8)     /* fold 64-bit archs */
9    if ((i&0xffffffff)==0) {
10      plus=32;
11      i>>=32;
12    }
13#endif
14  if ((i&0xffff)==0) {
15    plus+=16;
16    i>>=16;
17  }
18  if ((i&0xff)==0) {
19    plus+=8;
20    i>>=8;
21  }
22  if ((i&0xf)==0) {
23    plus+=4;
24    i>>=4;
25  }
26  if (i&1) return plus+1;
27  if (i&2) return plus+2;
28  if (i&4) return plus+3;
29  if (i&8) return plus+4;
30  return 0;
31}
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