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102 lines
2.4 KiB
102 lines
2.4 KiB
/*
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* Copyright (C) 2010 iptelorg GmbH
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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*/
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/** Kamailio core :: Implements the bit counting function:
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* Copyright (C) 2010 iptelorg GmbH
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* @ingroup core
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* Module: core
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*
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* int bit_count(unsigned int u)
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* Returns the number of bits in u.
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*/
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#ifndef _BIT_COUNT_H
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#define _BIT_COUNT_H
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/* fix __CPU_i386 -> __CPU_x86 */
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#if defined __CPU_i386 && ! defined __CPU_x86
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#define __CPU_x86
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#endif
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#ifdef CC_GCC_LIKE_ASM
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#if defined __CPU_x86 || defined __CPU_x86_64
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#ifdef __SSE4_2__
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/* popcnt requires SSE4.2 support,
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* see http://en.wikipedia.org/wiki/SSE4 */
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#define BIT_COUNT_ASM
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#endif
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#endif
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#endif
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#ifdef BIT_COUNT_ASM
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/* Returns the number of 1 bits in u. */
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static inline int bit_count(unsigned int u)
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{
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int v;
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asm volatile(" popcnt %1, %0 " : "=r" (v) : "rm" (u));
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return v;
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}
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#else /* BIT_COUNT_ASM */
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/* Returns the number of 1 bits in u.
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* source: http://en.wikipedia.org/wiki/Hamming_weight
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*/
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#if 0
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static inline int bit_count(unsigned int u)
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{
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int count;
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/* It is likely to have only few
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* bits set to 1, so there will be only
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* few iterations */
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for (count=0; u; count++)
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u &= u-1;
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return count;
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}
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#endif
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static inline int bit_count(unsigned int i)
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{
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i = i - ((i >> 1) & 0x55555555);
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i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
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return (((i + (i >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
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}
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#if 0
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/* number of bits in a byte.
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* (Only slightly faster then the above version,
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* It is not worth the extra memory usage.)
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*/
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extern int bits_in_char[256];
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static inline int bit_count(unsigned int u)
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{
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return bits_in_char [u & 0xffu]
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+ bits_in_char [(u >> 8 ) & 0xffu]
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+ bits_in_char [(u >> 16) & 0xffu]
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+ bits_in_char [(u >> 24) & 0xffu];
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}
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#endif
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#endif /* BIT_COUNT_ASM */
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#endif /* _BIT_COUNT_H */
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