/* Copyright (C) 2001-2017 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 */