diff options
Diffstat (limited to 'sysdeps/generic/ffs.c')
-rw-r--r-- | sysdeps/generic/ffs.c | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/sysdeps/generic/ffs.c b/sysdeps/generic/ffs.c new file mode 100644 index 0000000..06a1542 --- /dev/null +++ b/sysdeps/generic/ffs.c @@ -0,0 +1,55 @@ +/* Copyright (C) 1991, 1992, 1997, 1998, 2004 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Torbjorn Granlund (tege@sics.se). + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <limits.h> +#define ffsl __something_else +#include <string.h> + +#undef ffs + +/* Find the first bit set in I. */ +int +__ffs (i) + int i; +{ + static const unsigned char table[] = + { + 0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, + 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, + 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, + 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, + 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, + 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8 + }; + unsigned int a; + unsigned int x = i & -i; + + a = x <= 0xffff ? (x <= 0xff ? 0 : 8) : (x <= 0xffffff ? 16 : 24); + + return table[x >> a] + a; +} +weak_alias (__ffs, ffs) +libc_hidden_builtin_def (ffs) + +#if ULONG_MAX == UINT_MAX +#undef ffsl +weak_alias (__ffs, ffsl) +#endif |