1// Copyright 2013 Google Inc. All Rights Reserved. 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15// Helper function for bit twiddling 16 17#ifndef WOFF2_PORT_H_ 18#define WOFF2_PORT_H_ 19 20namespace woff2 { 21 22typedef unsigned int uint32; 23 24inline int Log2Floor(uint32 n) { 25#if defined(__GNUC__) 26 return n == 0 ? -1 : 31 ^ __builtin_clz(n); 27#else 28 if (n == 0) 29 return -1; 30 int log = 0; 31 uint32 value = n; 32 for (int i = 4; i >= 0; --i) { 33 int shift = (1 << i); 34 uint32 x = value >> shift; 35 if (x != 0) { 36 value = x; 37 log += shift; 38 } 39 } 40 assert(value == 1); 41 return log; 42#endif 43} 44 45} // namespace woff2 46#endif // WOFF2_PORT_H_ 47