Attachment 38867 Details for Bug 61405 – ffs.c

ffs.c

ffs.c (text/plain), 960 bytes, created by Colin Percival on 2004-01-16 04:00:34 UTC

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Creator: Colin Percival

Created: 2004-01-16 04:00:34 UTC

Size: 960 bytes

patch

obsolete

>#include <sys/types.h>
>
>static int ffslut32[] = {
>  32,  1, 23,  2, 29, 24, 14,  3,
>  30, 27, 25, 18, 20, 15, 10,  4,
>  31, 22, 28, 13, 26, 17, 19,  9,
>  21, 12, 16,  8, 11,  7,  6,  5
>};
>
>static int ffslut64[] = {
>  64,  1, 48,  2, 57, 49, 28,  3,
>  61, 58, 50, 42, 38, 29, 17,  4,
>  62, 55, 59, 36, 53, 51, 43, 22,
>  45, 39, 33, 30, 24, 18, 12,  5,
>  63, 47, 56, 27, 60, 41, 37, 16,
>  54, 35, 52, 21, 44, 32, 23, 11,
>  46, 26, 40, 15, 34, 20, 31, 10,
>  25, 14, 19,  9, 13,  8,  7,  6
>};
>
>static int ffs32(uint32_t mask)
>{
>  return mask ? ffslut32[((mask & (-mask)) * 0x0FB9AC52) >> 27] : 0;
>}
>
>static int ffs64(uint64_t mask)
>{
>  return mask ? ffslut64[((mask & (-mask)) * 0x07EF3AE369961512) >> 58] : 0;
>}
>
>int ffs(int mask)
>{
>  if (sizeof(int) == 8) return ffs64(mask);
>  if (sizeof(int) == 4) return ffs32(mask);
>  return -1;
>}
>
>int ffsl(long mask)
>{
>  if (sizeof(long) == 8) return ffs64(mask);
>  if (sizeof(long) == 4) return ffs32(mask);
>  return -1;
>}

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Attachments on bug 61405: 38867