Allow std::unordered_*.

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.
 //
 
 //
 // Deal with the differences between Microsoft and GNU implemenations
 // of hash_map. Allows all platforms to use |base::hash_map| and
 // |base::hash_set|.
 //  eg:
 //   base::hash_map<int> my_map;
 //   base::hash_set<int> my_set;
 //
 // NOTE: It is an explicit non-goal of this class to provide a generic hash
 // function for pointers.  If you want to hash a pointers to a particular class,
 // please define the template specialization elsewhere (for example, in its
 // header file) and keep it specific to just pointers to that class.  This is
 // because identity hashes are not desirable for all types that might show up
 // in containers as pointers.
 
 #ifndef BASE_CONTAINERS_HASH_TABLES_H_
 #define BASE_CONTAINERS_HASH_TABLES_H_
 
+#include <unordered_map>
+#include <unordered_set>
 #include <utility>
 
 #include "base/basictypes.h"
-#include "base/strings/string16.h"
-#include "build/build_config.h"
 
-#if defined(COMPILER_MSVC)
-#include <unordered_map>
-#include <unordered_set>
-
+// Deprecated. Specialize std::hash directly instead.
+// TODO(davidben): Or do we want to tell people to pass in a custom hasher?
+//
+// Things which specialize:
+// - base::trace_event::AllocationContext
+// - base::trace_event::BackTrace
+// - base::FilePath (hashes the string)
+// - base::StringPiece (hashes the string)
+// - cc::RenderPassId (custom pair-like type, defines a custom hasher, defined
+//   in wrong file)
+// - cc::SharedBitmapId (array, calls base::Hash, defined in wrong file, wrong
+//   module, even)
+// - cc::SurfaceId (wrapper over a uint64_t, hashes that)
+// - cc::SurfaceSequence (custom pair-like type)
+// - cc::TileMapKey (custom pair-like type with custom hash)
+// - content/renderer/pepper/v8_var_converter HashedHAndle (custom type with
+//   cached hash)
+// - content::GpuMemoryBufferConfigurationKey (should be same as default)
+// - data_reduction_proxy::ConnectionType (enum)
+// - gfx::GenericSharedMemoryId (hashes int)
+// - std::pair<gfx::GenericSharedMemoryId, Second> (unnecessary)
+// - gn internal::UniquifyRef (caches the hash in a hash_val_)
+// - gn Label (recursively calls std::hash)
+// - gn LabelPtrPair (just hashes the label, also defines operator==)
+// - gn OutputFile (hashes the string)
+// - gn SourceDir (hashes the string)
+// - gn SourceFile (hashes the string)
+// - media::MultiBufferGlobalBlockId (std::pair, should be same as default one)
+// - mojo::system::ChannelEndpointId (wrapper over integer)
+// - mojo::system::UniqueIdentifier
+// - net::DnsHostsKey (std::pair, but instead sums AddressFamily and StringPiece
+//   (not string?) hash)
+// - net::AlternativeService (custom thing, XORs stuff)
+// - net::QuicBlockedWriterInterface* (custom hash for a particular pointer, but
+//   only in GCC. I must have missed this last time.
+// - password_manager::FacetURI
+// - policy::PolicyNamespace (custom thing, hash string XOR 1<<enum)
+// - signin AccountId (hashes just the email)
+// - sync_file_system::drive_backend::ParentIDAndTitle (custom pair)
 #define BASE_HASH_NAMESPACE std
 
-#elif defined(COMPILER_GCC)
-
-#define BASE_HASH_NAMESPACE base_hash
-
-// 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 <ext/hash_map>
-#include <ext/hash_set>
-#define BASE_HASH_IMPL_NAMESPACE __gnu_cxx
-
-#include <string>
-
-#ifdef CHROME_OLD__DEPRECATED
-#define __DEPRECATED CHROME_OLD__DEPRECATED
-#undef CHROME_OLD__DEPRECATED
-#endif
-
-namespace BASE_HASH_NAMESPACE {
-
-// The pre-standard hash behaves like C++11's std::hash, except around pointers.
-// const char* is specialized to hash the C string and hash functions for
-// general T* are missing. Define a BASE_HASH_NAMESPACE::hash which aligns with
-// the C++11 behavior.
-
-template<typename T>
-struct hash {
-  std::size_t operator()(const T& value) const {
-    return BASE_HASH_IMPL_NAMESPACE::hash<T>()(value);
-  }
-};
-
-template<typename T>
-struct hash<T*> {
-  std::size_t operator()(T* value) const {
-    return BASE_HASH_IMPL_NAMESPACE::hash<uintptr_t>()(
-        reinterpret_cast<uintptr_t>(value));
-  }
-};
-
-// 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); \
-      } \
-    }
-
-DEFINE_TRIVIAL_HASH(long long);
-DEFINE_TRIVIAL_HASH(unsigned long long);
-
-#undef DEFINE_TRIVIAL_HASH
-
-// 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; \
-      } \
-    }
-
-DEFINE_STRING_HASH(std::string);
-DEFINE_STRING_HASH(base::string16);
-
-#undef DEFINE_STRING_HASH
-
-}  // namespace BASE_HASH_NAMESPACE
-
-#else  // COMPILER
-#error define BASE_HASH_NAMESPACE for your compiler
-#endif  // COMPILER
-
 namespace base {
 
-// On MSVC, use the C++11 containers.
-#if defined(COMPILER_MSVC)
-
+// Deprecated. Use std::unordered_map instead.
 template<class Key, class T,
          class Hash = std::hash<Key>,
          class Pred = std::equal_to<Key>,
          class Alloc = std::allocator<std::pair<const Key, T>>>
 using hash_map = std::unordered_map<Key, T, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_multimap instead.
 template<class Key, class T,
          class Hash = std::hash<Key>,
          class Pred = std::equal_to<Key>,
          class Alloc = std::allocator<std::pair<const Key, T>>>
 using hash_multimap = std::unordered_multimap<Key, T, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_multiset instead.
 template<class Key,
          class Hash = std::hash<Key>,
          class Pred = std::equal_to<Key>,
          class Alloc = std::allocator<Key>>
 using hash_multiset = std::unordered_multiset<Key, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_set instead.
 template<class Key,
          class Hash = std::hash<Key>,
          class Pred = std::equal_to<Key>,
          class Alloc = std::allocator<Key>>
 using hash_set = std::unordered_set<Key, Hash, Pred, Alloc>;
 
-#else  // !COMPILER_MSVC
-
-// Otherwise, use the pre-standard ones, but override the default hash to match
-// C++11.
-template<class Key, class T,
-         class Hash = BASE_HASH_NAMESPACE::hash<Key>,
-         class Pred = std::equal_to<Key>,
-         class Alloc = std::allocator<std::pair<const Key, T>>>
-using hash_map = BASE_HASH_IMPL_NAMESPACE::hash_map<Key, T, Hash, Pred, Alloc>;
-
-template<class Key, class T,
-         class Hash = BASE_HASH_NAMESPACE::hash<Key>,
-         class Pred = std::equal_to<Key>,
-         class Alloc = std::allocator<std::pair<const Key, T>>>
-using hash_multimap =
-    BASE_HASH_IMPL_NAMESPACE::hash_multimap<Key, T, Hash, Pred, Alloc>;
-
-template<class Key,
-         class Hash = BASE_HASH_NAMESPACE::hash<Key>,
-         class Pred = std::equal_to<Key>,
-         class Alloc = std::allocator<Key>>
-using hash_multiset =
-    BASE_HASH_IMPL_NAMESPACE::hash_multiset<Key, Hash, Pred, Alloc>;
-
-template<class Key,
-         class Hash = BASE_HASH_NAMESPACE::hash<Key>,
-         class Pred = std::equal_to<Key>,
-         class Alloc = std::allocator<Key>>
-using hash_set = BASE_HASH_IMPL_NAMESPACE::hash_set<Key, Hash, Pred, Alloc>;
-
-#undef BASE_HASH_IMPL_NAMESPACE
-
-#endif  // COMPILER_MSVC
-
 // Implement hashing for pairs of at-most 32 bit integer values.
 // When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using
 // multiply-add hashing. This algorithm, as described in
 // Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in
 // eingeschränkten Branchingprogrammmodellen" by Woelfel, is:
 //
 //   h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32
 //
 // Contact danakj@chromium.org for any questions.
 inline std::size_t HashInts32(uint32 value1, uint32 value2) {
@@ skipping 57 matching lines @@
   return HashInts32(value1, value2);
 }
 
 }  // namespace base
 
 namespace BASE_HASH_NAMESPACE {
 
 // Implement methods for hashing a pair of integers, so they can be used as
 // keys in STL containers.
 
+// TODO(davidben): This is not present in C++11. How to transition this tidily?
+// Should we keep a header around that specializes for std::pair (poor as it is
+// not the same header std::pair is defined in) or ask people to pass in the
+// third argument. I'm tempted to say the latter.
 template<typename Type1, typename Type2>
 struct hash<std::pair<Type1, Type2> > {
   std::size_t operator()(std::pair<Type1, Type2> value) const {
     return base::HashPair(value.first, value.second);
   }
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
-#undef DEFINE_PAIR_HASH_FUNCTION_START
-#undef DEFINE_PAIR_HASH_FUNCTION_END
-
 #endif  // BASE_CONTAINERS_HASH_TABLES_H_