176 lines
3.9 KiB
C
176 lines
3.9 KiB
C
/* bits.h - bits functions.
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*
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* Copyright (C) 2021-2022 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*
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*/
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#ifndef BITS_H
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#define BITS_H
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#include <stdint.h>
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/* next include will define __WORDSIZE: 32 or 64
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*/
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#include <bits/wordsize.h>
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#ifndef __has_builtin
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#define __has_builtin(x) 0
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#endif
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/* no plan to support 32bits for now...
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*/
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#if __WORDSIZE != 64
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#error "Only 64 bits word size supported."
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#endif
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typedef int64_t s64;
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typedef int32_t s32;
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typedef int16_t s16;
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typedef int8_t s8;
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typedef uint64_t u64;
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typedef uint32_t u32;
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typedef uint16_t u16;
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typedef uint8_t u8;
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typedef unsigned long int ulong;
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typedef unsigned int uint;
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typedef unsigned short ushort;
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typedef unsigned char uchar;
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typedef signed long int slong;
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typedef signed int sint;
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typedef signed short sshort;
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typedef signed char schar;
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/* count trailing zeroes : 00101000 -> 3
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* ^^^
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*/
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static inline int ctz64(u64 n)
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{
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# if __has_builtin(__builtin_ctzl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin ctzl.\n");
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# endif
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return __builtin_ctzl(n);
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# elif __has_builtin(__builtin_clzl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin clzl.\n");
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# endif
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return __WORDSIZE - (__builtin_clzl(n & -n) + 1);
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# else
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# ifdef DEBUG_BITS
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log_f(1, "emulated.\n");
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# endif
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return popcount64((n & −n) − 1);
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# endif
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}
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/* count leading zeroes : 00101000 -> 2
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* ^^
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*/
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static inline int clz64(u64 n)
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{
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# if __has_builtin(__builtin_clzl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin.\n");
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# endif
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return __builtin_clzl(n);
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# else
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# ifdef DEBUG_BITS
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log_f(1, "emulated.\n");
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# endif
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u64 r, q;
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r = (n > 0xFFFFFFFF) << 5; n >>= r;
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q = (n > 0xFFFF) << 4; n >>= q; r |= q;
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q = (n > 0xFF ) << 3; n >>= q; r |= q;
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q = (n > 0xF ) << 2; n >>= q; r |= q;
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q = (n > 0x3 ) << 1; n >>= q; r |= q;
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r |= (n >> 1);
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return __WORDSIZE - r - 1;
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# endif
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}
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/* find first set : 00101000 -> 4
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* ^
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*/
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static inline uint ffs64(u64 n)
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{
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# if __has_builtin(__builtin_ffsl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin ffsl.\n");
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# endif
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return __builtin_ffsll(n);
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# elif __has_builtin(__builtin_ctzl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin ctzl.\n");
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# endif
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if (n == 0)
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return (0);
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return __builtin_ctzl(n) + 1;
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# else
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# ifdef DEBUG_BITS
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log_f(1, "emulated.\n");
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# endif
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return popcount64(n ^ ~-n);
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# endif
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}
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static inline int popcount64(u64 n)
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{
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# if __has_builtin(__builtin_popcountl)
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# ifdef DEBUG_BITS
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log_f(1, "builtin.\n");
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# endif
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return __builtin_popcountl(n);
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# else
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# ifdef DEBUG_BITS
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log_f(1, "emulated.\n");
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# endif
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int count = 0;
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while (n) {
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count++;
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n &= (n - 1);
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}
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return count;
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# endif
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}
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/** bit_for_each64 - iterate over an u64 bits
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* @pos: an int used as current bit
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* @tmp: a temp u64 used as temporary storage
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* @ul: the u64 to loop over
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*
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* Usage:
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* u64 u=139, _t; // u=b10001011
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* int cur;
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* bit_for_each64(cur, _t, u) {
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* printf("%d\n", cur);
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* }
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* This will display the position of each bit set in ul: 1, 2, 4, 8
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*
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* I should probably re-think the implementation...
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*/
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#define bit_for_each64(pos, tmp, ul) \
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for (tmp = ul, pos = ffs64(tmp); tmp; tmp &= (tmp - 1), pos = ffs64(tmp))
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/** or would it be more useful (counting bits from zero instead of 1) ?
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*/
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#define bit_for_each64_2(pos, tmp, ul) \
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for (tmp = ul, pos = ctz64(tmp); tmp; tmp ^= 1UL<<pos, pos = ctz64(tmp))
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#endif /* BITS_H */
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