1 /**************************************************************************
3 * Copyright 2008 VMware, Inc.
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
26 **************************************************************************/
40 #include "c99_compat.h"
48 * Find first bit set in word. Least significant bit is 1.
49 * Return 0 if no bits set.
51 #ifdef HAVE___BUILTIN_FFS
52 #define ffs __builtin_ffs
53 #elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
58 if (_BitScanForward(&index
, i
))
68 #ifdef HAVE___BUILTIN_FFSLL
69 #define ffsll __builtin_ffsll
70 #elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM || _M_IA64)
72 ffsll(long long int i
)
75 if (_BitScanForward64(&index
, i
))
82 ffsll(long long int val
);
86 /* Destructively loop over all of the bits in a mask as in:
89 * int i = u_bit_scan(&mymask);
90 * ... process element i
95 u_bit_scan(unsigned *mask
)
97 const int i
= ffs(*mask
) - 1;
103 u_bit_scan64(uint64_t *mask
)
105 const int i
= ffsll(*mask
) - 1;
106 *mask
^= (((uint64_t)1) << i
);
110 /* For looping over a bitmask when you want to loop over consecutive bits
111 * manually, for example:
114 * int start, count, i;
116 * u_bit_scan_consecutive_range(&mask, &start, &count);
118 * for (i = 0; i < count; i++)
119 * ... process element (start+i)
123 u_bit_scan_consecutive_range(unsigned *mask
, int *start
, int *count
)
125 if (*mask
== 0xffffffff) {
131 *start
= ffs(*mask
) - 1;
132 *count
= ffs(~(*mask
>> *start
)) - 1;
133 *mask
&= ~(((1u << *count
) - 1) << *start
);
137 u_bit_scan_consecutive_range64(uint64_t *mask
, int *start
, int *count
)
139 if (*mask
== ~0ull) {
145 *start
= ffsll(*mask
) - 1;
146 *count
= ffsll(~(*mask
>> *start
)) - 1;
147 *mask
&= ~(((((uint64_t)1) << *count
) - 1) << *start
);
152 * Find last bit set in a word. The least significant bit is 1.
153 * Return 0 if no bits are set.
154 * Essentially ffs() in the reverse direction.
156 static inline unsigned
157 util_last_bit(unsigned u
)
159 #if defined(HAVE___BUILTIN_CLZ)
160 return u
== 0 ? 0 : 32 - __builtin_clz(u
);
161 #elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
163 if (_BitScanReverse(&index
, u
))
178 * Find last bit set in a word. The least significant bit is 1.
179 * Return 0 if no bits are set.
180 * Essentially ffsll() in the reverse direction.
182 static inline unsigned
183 util_last_bit64(uint64_t u
)
185 #if defined(HAVE___BUILTIN_CLZLL)
186 return u
== 0 ? 0 : 64 - __builtin_clzll(u
);
187 #elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM || _M_IA64)
189 if (_BitScanReverse64(&index
, u
))
204 * Find last bit in a word that does not match the sign bit. The least
205 * significant bit is 1.
206 * Return 0 if no bits are set.
208 static inline unsigned
209 util_last_bit_signed(int i
)
212 return util_last_bit(i
);
214 return util_last_bit(~(unsigned)i
);
217 /* Returns a bitfield in which the first count bits starting at start are
220 static inline unsigned
221 u_bit_consecutive(unsigned start
, unsigned count
)
223 assert(start
+ count
<= 32);
226 return ((1u << count
) - 1) << start
;
229 static inline uint64_t
230 u_bit_consecutive64(unsigned start
, unsigned count
)
232 assert(start
+ count
<= 64);
235 return (((uint64_t)1 << count
) - 1) << start
;
243 #endif /* BITSCAN_H */