/src/guetzli/guetzli/fast_log.h
Line | Count | Source |
1 | | /* |
2 | | * Copyright 2016 Google Inc. |
3 | | * |
4 | | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | | * you may not use this file except in compliance with the License. |
6 | | * You may obtain a copy of the License at |
7 | | * |
8 | | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | | * |
10 | | * Unless required by applicable law or agreed to in writing, software |
11 | | * distributed under the License is distributed on an "AS IS" BASIS, |
12 | | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
13 | | * See the License for the specific language governing permissions and |
14 | | * limitations under the License. |
15 | | */ |
16 | | |
17 | | #ifndef GUETZLI_FAST_LOG_H_ |
18 | | #define GUETZLI_FAST_LOG_H_ |
19 | | |
20 | | #include <math.h> |
21 | | |
22 | | namespace guetzli { |
23 | | |
24 | 187M | inline int Log2FloorNonZero(uint32_t n) { |
25 | 187M | #ifdef __GNUC__ |
26 | 187M | return 31 ^ __builtin_clz(n); |
27 | | #else |
28 | | unsigned int result = 0; |
29 | | while (n >>= 1) result++; |
30 | | return result; |
31 | | #endif |
32 | 187M | } |
33 | | |
34 | 17.9M | inline int Log2Floor(uint32_t n) { |
35 | 17.9M | return n == 0 ? -1 : Log2FloorNonZero(n); |
36 | 17.9M | } |
37 | | |
38 | | } // namespace guetzli |
39 | | |
40 | | #endif // GUETZLI_FAST_LOG_H_ |