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bitops.h
Go to the documentation of this file.
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/*
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* Copyright (c) 2015 Cisco and/or its affiliates.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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Copyright (c) 2005 Eliot Dresselhaus
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef included_clib_bitops_h
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#define included_clib_bitops_h
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#include <
vppinfra/clib.h
>
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/* Population count from Hacker's Delight. */
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always_inline
uword
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count_set_bits
(
uword
x)
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{
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#if uword_bits == 64
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const
uword
c1 = 0x5555555555555555;
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const
uword
c2 = 0x3333333333333333;
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const
uword
c3 = 0x0f0f0f0f0f0f0f0f;
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#else
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const
uword
c1 = 0x55555555;
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const
uword
c2 = 0x33333333;
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const
uword
c3 = 0x0f0f0f0f;
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#endif
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/* Sum 1 bit at a time. */
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x = x - ((x >> (
uword
) 1) & c1);
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/* 2 bits at a time. */
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x = (x & c2) + ((x >> (
uword
) 2) & c2);
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/* 4 bits at a time. */
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x = (x + (x >> (
uword
) 4)) & c3;
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/* 8, 16, 32 bits at a time. */
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x = x + (x >> (
uword
) 8);
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x = x + (x >> (
uword
) 16);
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#if uword_bits == 64
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x = x + (x >> (
uword
) 32);
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#endif
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return
x & (2 *
BITS
(
uword
) - 1);
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}
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/* Based on "Hacker's Delight" code from GLS. */
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typedef
struct
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{
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uword
masks[1 +
log2_uword_bits
];
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}
compress_main_t
;
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always_inline
void
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compress_init
(
compress_main_t
* cm,
uword
mask)
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{
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uword
q, m, zm, n,
i
;
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m = ~mask;
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zm = mask;
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cm->
masks
[0] = mask;
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for
(i = 0; i <
log2_uword_bits
; i++)
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{
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q = m;
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m ^= m << 1;
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m ^= m << 2;
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m ^= m << 4;
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m ^= m << 8;
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m ^= m << 16;
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#if uword_bits > 32
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m ^= m << (
uword
) 32;
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#endif
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cm->
masks
[1 +
i
] = n = (m << 1) & zm;
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m = q & ~m;
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q = zm & n;
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zm = zm ^ q ^ (q >> (1 <<
i
));
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}
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}
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always_inline
uword
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compress_bits
(
compress_main_t
* cm,
uword
x)
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{
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uword
q, r;
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r = x & cm->
masks
[0];
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q = r & cm->
masks
[1];
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r ^= q ^ (q >> 1);
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q = r & cm->
masks
[2];
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r ^= q ^ (q >> 2);
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q = r & cm->
masks
[3];
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r ^= q ^ (q >> 4);
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q = r & cm->
masks
[4];
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r ^= q ^ (q >> 8);
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q = r & cm->
masks
[5];
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r ^= q ^ (q >> 16);
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#if uword_bits > 32
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q = r & cm->
masks
[6];
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r ^= q ^ (q >> (
uword
) 32);
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#endif
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return
r;
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}
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always_inline
uword
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rotate_left
(
uword
x,
uword
i
)
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{
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return
(x << i) | (x >> (
BITS
(i) -
i
));
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}
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always_inline
uword
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rotate_right
(
uword
x,
uword
i
)
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{
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return
(x >> i) | (x << (
BITS
(i) -
i
));
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}
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/* Returns snoob from Hacker's Delight. Next highest number
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with same number of set bits. */
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always_inline
uword
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next_with_same_number_of_set_bits
(
uword
x)
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{
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uword
smallest, ripple, ones;
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smallest = x & -x;
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ripple = x + smallest;
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ones = x ^ ripple;
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ones = ones >> (2 +
log2_first_set
(x));
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return
ripple | ones;
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}
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#define foreach_set_bit(var,mask,body) \
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do { \
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uword _foreach_set_bit_m_##var = (mask); \
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uword _foreach_set_bit_f_##var; \
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while (_foreach_set_bit_m_##var != 0) \
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{ \
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_foreach_set_bit_f_##var = first_set (_foreach_set_bit_m_##var); \
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_foreach_set_bit_m_##var ^= _foreach_set_bit_f_##var; \
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(var) = min_log2 (_foreach_set_bit_f_##var); \
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do { body; } while (0); \
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} \
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} while (0)
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#endif
/* included_clib_bitops_h */
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/*
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* fd.io coding-style-patch-verification: ON
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*
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* Local Variables:
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* eval: (c-set-style "gnu")
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* End:
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*/
i
sll srl srl sll sra u16x4 i
Definition:
vector_sse2.h:337
log2_first_set
static uword log2_first_set(uword x)
Definition:
clib.h:304
log2_uword_bits
#define log2_uword_bits
Definition:
types.h:84
compress_init
static void compress_init(compress_main_t *cm, uword mask)
Definition:
bitops.h:83
always_inline
#define always_inline
Definition:
clib.h:92
clib.h
rotate_right
static uword rotate_right(uword x, uword i)
Definition:
bitops.h:140
uword
u64 uword
Definition:
types.h:112
compress_main_t
Definition:
bitops.h:77
count_set_bits
static uword count_set_bits(uword x)
Definition:
bitops.h:45
compress_main_t::masks
uword masks[1+log2_uword_bits]
Definition:
bitops.h:79
BITS
#define BITS(x)
Definition:
clib.h:58
compress_bits
static uword compress_bits(compress_main_t *cm, uword x)
Definition:
bitops.h:110
rotate_left
static uword rotate_left(uword x, uword i)
Definition:
bitops.h:134
next_with_same_number_of_set_bits
static uword next_with_same_number_of_set_bits(uword x)
Definition:
bitops.h:148
src
vppinfra
bitops.h
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