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/* Copyright (C) 2001-2019 Peter Selinger.
This file is part of Potrace. It is free software and it is covered
by the GNU General Public License. See the file COPYING for details. */
/* bits.h: this file defines some macros for bit manipulations. We
provide a generic implementation, as well as machine- and
compiler-specific fast implementations */
/* lobit: return the position of the rightmost "1" bit of an int, or
32 if none. hibit: return 1 + the position of the leftmost "1" bit
of an int, or 0 if none. Note: these functions work on 32-bit
integers. */
#ifndef BITOPS_H
#define BITOPS_H
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
/* ---------------------------------------------------------------------- */
/* machine specific macros */
#if defined(HAVE_I386)
static inline unsigned int lobit(unsigned int x) {
unsigned int res;
asm ("bsf %1,%0\n\t"
"jnz 0f\n\t"
"movl $32,%0\n"
"0:"
: "=r" (res)
: "r" (x)
: "cc");
return res;
}
static inline unsigned int hibit(unsigned int x) {
unsigned int res;
asm ("bsr %1,%0\n\t"
"jnz 0f\n\t"
"movl $-1,%0\n"
"0:"
: "=r" (res)
: "r" (x)
: "cc");
return res+1;
}
/* ---------------------------------------------------------------------- */
#else /* generic macros */
static inline unsigned int lobit(unsigned int x) {
unsigned int res = 32;
while (x & 0xffffff) {
x <<= 8;
res -= 8;
}
while (x) {
x <<= 1;
res -= 1;
}
return res;
}
static inline unsigned int hibit(unsigned int x) {
unsigned int res = 0;
while (x > 0xff) {
x >>= 8;
res += 8;
}
while (x) {
x >>= 1;
res += 1;
}
return res;
}
#endif
#endif /* BITOPS_H */
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