base/containers/hash_tables.h

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_CONTAINERS_HASH_TABLES_H_
#define BASE_CONTAINERS_HASH_TABLES_H_

#include <cstddef>
#include <unordered_map>
#include <unordered_set>
#include <utility>

#include "base/hash.h"

// This header file is deprecated. Use the corresponding C++11 type
// instead. https://crbug.com/576864

// Chromium has moved away from compiler specific hash methods and instead uses
// std::hashes unconditionally. Starboard sadly does not guarantee std::hash.
#if defined(STARBOARD)
#include "starboard/configuration.h"
#define BASE_HASH_DEFINE_LONG_LONG_HASHES 0
#define BASE_HASH_DEFINE_STRING_HASHES 0
#define BASE_HASH_USE_HASH 0
#define BASE_HASH_MAP_INCLUDE <unordered_map>
#define BASE_HASH_NAMESPACE std
#define BASE_HASH_SET_INCLUDE <unordered_set>
#define BASE_HASH_USE_HASH_STRUCT

#elif defined(COMPILER_GCC)
#if defined(OS_ANDROID) || (defined(__LB_SHELL__) && !defined(__LB_LINUX__))
#define BASE_HASH_DEFINE_LONG_LONG_HASHES 0
#define BASE_HASH_DEFINE_STRING_HASHES !defined(__LB_SHELL__)
#define BASE_HASH_MAP_INCLUDE <hash_map>
#define BASE_HASH_NAMESPACE std
#define BASE_HASH_SET_INCLUDE <hash_set>
#else
#define BASE_HASH_DEFINE_LONG_LONG_HASHES 1
#define BASE_HASH_DEFINE_STRING_HASHES 1
#define BASE_HASH_MAP_INCLUDE <ext/hash_map>
#define BASE_HASH_NAMESPACE __gnu_cxx
#define BASE_HASH_SET_INCLUDE <ext/hash_set>
#define BASE_HASH_USE_HASH_STRUCT
#endif
#if defined(__LB_LINUX__)
#define BASE_HASH_USE_HASH 1
#else
#define BASE_HASH_USE_HASH 0
#endif
#else  // COMPILER
#error define BASE_HASH_NAMESPACE for your compiler
#endif  // COMPILER

// This is a hack to disable the gcc 4.4 warning about hash_map and hash_set
// being deprecated.  We can get rid of this when we upgrade to VS2008 and we
// can use <tr1/unordered_map> and <tr1/unordered_set>.
#ifdef __DEPRECATED
#define CHROME_OLD__DEPRECATED __DEPRECATED
#undef __DEPRECATED
#endif

#include BASE_HASH_MAP_INCLUDE
#include BASE_HASH_SET_INCLUDE

#ifdef CHROME_OLD__DEPRECATED
#define __DEPRECATED CHROME_OLD__DEPRECATED
#undef CHROME_OLD__DEPRECATED
#endif

#if BASE_HASH_DEFINE_LONG_LONG_HASHES
// The GNU C++ library provides identity hash functions for many integral types,
// but not for |long long|.  This hash function will truncate if |size_t| is
// narrower than |long long|.  This is probably good enough for what we will
// use it for.

#define DEFINE_TRIVIAL_HASH(integral_type)              \
  template <>                                           \
  struct hash<integral_type> {                          \
    std::size_t operator()(integral_type value) const { \
      return static_cast<std::size_t>(value);           \
    }                                                   \
  }

namespace BASE_HASH_NAMESPACE {
DEFINE_TRIVIAL_HASH(long long);
DEFINE_TRIVIAL_HASH(unsigned long long);

template <typename T>
struct hash<T*> {
  std::size_t operator()(T* value) const {
    return BASE_HASH_NAMESPACE::hash<uintptr_t>()(
        reinterpret_cast<uintptr_t>(value));
  }
};
}  // namespace BASE_HASH_NAMESPACE

#undef DEFINE_TRIVIAL_HASH
#endif  // BASE_HASH_DEFINE_LONG_LONG_HASHES

#if BASE_HASH_DEFINE_STRING_HASHES
// Implement string hash functions so that strings of various flavors can
// be used as keys in STL maps and sets.  The hash algorithm comes from the
// GNU C++ library, in <tr1/functional>.  It is duplicated here because GCC
// versions prior to 4.3.2 are unable to compile <tr1/functional> when RTTI
// is disabled, as it is in our build.

#define DEFINE_STRING_HASH(string_type)                                  \
  template <>                                                            \
  struct hash<string_type> {                                             \
    std::size_t operator()(const string_type& s) const {                 \
      std::size_t result = 0;                                            \
      for (string_type::const_iterator i = s.begin(); i != s.end(); ++i) \
        result = (result * 131) + *i;                                    \
      return result;                                                     \
    }                                                                    \
  }

namespace BASE_HASH_NAMESPACE {
DEFINE_STRING_HASH(std::string);
DEFINE_STRING_HASH(base::string16);

// Use base::IntPairHash from base/hash.h as a custom hasher instead.
template <typename Type1, typename Type2>
struct hash<std::pair<Type1, Type2>> {
  std::size_t operator()(std::pair<Type1, Type2> value) const {
    return base::HashInts(value.first, value.second);
  }
};

}  // namespace BASE_HASH_NAMESPACE

#undef DEFINE_STRING_HASH
#endif  // BASE_HASH_DEFINE_STRING_HASHES

namespace base {
#if BASE_HASH_USE_HASH
using BASE_HASH_NAMESPACE::hash;
#endif
template <class K,
          class V,
          class Hash = std::hash<K>,
          class KeyEqual = std::equal_to<K>>
using hash_map = std::unordered_map<K, V, Hash, KeyEqual>;
template <class K,
          class V,
          class Hash = std::hash<K>,
          class KeyEqual = std::equal_to<K>>
using hash_multimap = std::unordered_multimap<K, V, Hash, KeyEqual>;
template <class K, class Hash = std::hash<K>, class KeyEqual = std::equal_to<K>>
using hash_multiset = std::unordered_multiset<K, Hash, KeyEqual>;
template <class K, class Hash = std::hash<K>, class KeyEqual = std::equal_to<K>>
using hash_set = std::unordered_set<K, Hash, KeyEqual>;
}

#undef BASE_HASH_DEFINE_LONG_LONG_HASHES
#undef BASE_HASH_DEFINE_STRING_HASHES
#undef BASE_HASH_MAP_INCLUDE
#undef BASE_HASH_SET_INCLUDE
#undef BASE_HASH_USE_HASH

#endif  // BASE_HASH_TABLES_H_