port.h - mozsearch

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/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.

   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT

*/

/* 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

#if (defined(__ARM_ARCH) && (__ARM_ARCH == 7)) || \

    (defined(M_ARM) && (M_ARM == 7)) || \

    defined(__aarch64__) || defined(__ARM64_ARCH_8__) || defined(__i386) || \

    defined(_M_IX86) || defined(__x86_64__) || defined(_M_X64)

#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)

#define WOFF_LITTLE_ENDIAN

#elif defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)

#define WOFF_BIG_ENDIAN

#endif  /* endianness */

#endif  /* CPU whitelist */

#endif  // WOFF2_PORT_H_