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// Copyright 2013 Google Inc. All Rights Reserved.
//
// 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.
//
// Helper function for bit twiddling and macros for branch prediction.
#ifndef WOFF2_PORT_H_
#define WOFF2_PORT_H_
#include <assert.h>
namespace woff2 {
typedef unsigned int uint32;
inline int Log2Floor(uint32 n) {
#if defined(__GNUC__)
return n == 0 ? -1 : 31 ^ __builtin_clz(n);
#else
if (n == 0)
return -1;
int log = 0;
uint32 value = n;
for (int i = 4; i >= 0; --i) {
int shift = (1 << i);
uint32 x = value >> shift;
if (x != 0) {
value = x;
log += shift;
}
}
assert(value == 1);
return log;
#endif
}
} // namespace woff2
/* Compatibility with non-clang compilers. */
#ifndef __has_builtin
#define __has_builtin(x) 0
#endif
#if (__GNUC__ > 2) || (__GNUC__ == 2 && __GNUC_MINOR__ > 95) || \
(defined(__llvm__) && __has_builtin(__builtin_expect))
#define PREDICT_FALSE(x) (__builtin_expect(x, 0))
#define PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
#else
#define PREDICT_FALSE(x) (x)
#define PREDICT_TRUE(x) (x)
#endif
#endif // WOFF2_PORT_H_
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