blob: d4a9a5a988287db57bc4d0f65102e7ed78bcf61e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Copyright 2005-2010 Google, Inc.
// Author: sorenj@google.com (Jeffrey Sorensen)
// dr@google.com (Doug Rohde)
#ifndef FST_EXTENSIONS_NGRAM_NTHBIT_H_
#define FST_EXTENSIONS_NGRAM_NTHBIT_H_
#include <fst/types.h>
extern uint32 nth_bit_bit_offset[];
inline uint32 nth_bit(uint64 v, uint32 r) {
uint32 shift = 0;
uint32 c = __builtin_popcount(v & 0xffffffff);
uint32 mask = -(r > c);
r -= c & mask;
shift += (32 & mask);
c = __builtin_popcount((v >> shift) & 0xffff);
mask = -(r > c);
r -= c & mask;
shift += (16 & mask);
c = __builtin_popcount((v >> shift) & 0xff);
mask = -(r > c);
r -= c & mask;
shift += (8 & mask);
return shift + ((nth_bit_bit_offset[(v >> shift) & 0xff] >>
((r - 1) << 2)) & 0xf);
}
#endif // FST_EXTENSIONS_NGRAM_NTHBIT_H_
|
