103 lines
1.9 KiB
C
103 lines
1.9 KiB
C
/* Copyright (C) 2001-2015 Peter Selinger.
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* This file is part of Potrace. It is free software and it is covered
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* by the GNU General Public License. See the file COPYING for details. */
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/* bits.h: this file defines some macros for bit manipulations. We
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* provide a generic implementation, as well as machine- and
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* compiler-specific fast implementations */
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/* lobit: return the position of the rightmost "1" bit of an int, or
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* 32 if none. hibit: return 1 + the position of the leftmost "1" bit
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* of an int, or 0 if none. Note: these functions work on 32-bit
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* integers. */
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#ifndef BITOPS_H
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#define BITOPS_H
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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/* ---------------------------------------------------------------------- */
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/* machine specific macros */
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#if defined(HAVE_I386)
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static inline unsigned int lobit( unsigned int x )
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{
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unsigned int res;
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asm ("bsf %1,%0\n\t"
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"jnz 0f\n\t"
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"movl $32,%0\n"
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"0:"
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: "=r" (res)
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: "r" (x)
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: "cc");
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return res;
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}
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static inline unsigned int hibit( unsigned int x )
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{
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unsigned int res;
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asm ("bsr %1,%0\n\t"
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"jnz 0f\n\t"
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"movl $-1,%0\n"
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"0:"
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: "=r" (res)
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: "r" (x)
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: "cc");
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return res + 1;
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}
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/* ---------------------------------------------------------------------- */
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#else /* generic macros */
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static inline unsigned int lobit( unsigned int x )
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{
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unsigned int res = 32;
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while( x & 0xffffff )
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{
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x <<= 8;
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res -= 8;
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}
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while( x )
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{
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x <<= 1;
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res -= 1;
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}
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return res;
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}
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static inline unsigned int hibit( unsigned int x )
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{
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unsigned int res = 0;
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while( x > 0xff )
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{
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x >>= 8;
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res += 8;
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}
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while( x )
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{
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x >>= 1;
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res += 1;
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}
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return res;
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}
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#endif
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#endif /* BITOPS_H */
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