third_party/woff2/src/port.h

   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
  20 namespace woff2 {
  21
  22 typedef unsigned int       uint32;
  23
  24 inline 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_