2 * bitops.h - inline functions for bit manipulation
4 * Copyright 2022 Eric Biggers
6 * Permission is hereby granted, free of charge, to any person
7 * obtaining a copy of this software and associated documentation
8 * files (the "Software"), to deal in the Software without
9 * restriction, including without limitation the rights to use,
10 * copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following
15 * The above copyright notice and this permission notice shall be
16 * included in all copies or substantial portions of the Software.
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
20 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
22 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
23 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
24 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
25 * OTHER DEALINGS IN THE SOFTWARE.
28 #ifndef _WIMLIB_BITOPS_H
29 #define _WIMLIB_BITOPS_H
31 #include "wimlib/compiler.h"
32 #include "wimlib/types.h"
35 * Bit Scan Reverse (BSR) - find the 0-based index (relative to the least
36 * significant bit) of the *most* significant 1 bit in the input value. The
37 * input value must be nonzero!
40 static forceinline unsigned
43 return 31 - __builtin_clz(v);
46 static forceinline unsigned
49 return 63 - __builtin_clzll(v);
52 static forceinline unsigned
53 bsrw(machine_word_t v)
55 STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);
63 * Bit Scan Forward (BSF) - find the 0-based index (relative to the least
64 * significant bit) of the *least* significant 1 bit in the input value. The
65 * input value must be nonzero!
68 static forceinline unsigned
71 return __builtin_ctz(v);
74 static forceinline unsigned
77 return __builtin_ctzll(v);
80 static forceinline unsigned
81 bsfw(machine_word_t v)
83 STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);
90 /* Return the log base 2 of 'n', rounded up to the nearest integer. */
91 static forceinline unsigned
96 return 1 + bsrw(n - 1);
99 /* Round 'n' up to the nearest power of 2 */
100 static forceinline size_t
101 roundup_pow_of_2(size_t n)
103 return (size_t)1 << ilog2_ceil(n);
106 #endif /* _WIMLIB_BITOPS_H */