File indexing completed on 2024-12-22 04:04:10

 /* 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 */