Allow std::unordered_*.

base/containers/hash_tables.h

Index: base/containers/hash_tables.h
diff --git a/base/containers/hash_tables.h b/base/containers/hash_tables.h
index c421dddf3e7c707beb1c57d72865a32376f6d9db..f23938eb6c976522138049aa22d08520c961d8c5 100644
--- a/base/containers/hash_tables.h
+++ b/base/containers/hash_tables.h
@@ -3,279 +3,72 @@
 // 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 <stddef.h>
-#include <stdint.h>
-
-#include <utility>
-
-#include "base/strings/string16.h"
-#include "build/build_config.h"
-
-#if defined(COMPILER_MSVC)
+#include <cstddef>
 #include <unordered_map>
 #include <unordered_set>
+#include <utility>
 
-#define BASE_HASH_NAMESPACE std
-
-#elif defined(COMPILER_GCC)
+#include "base/containers/pair_hash.h"
 
+// Deprecated. Use a custom hasher instead.
 #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.
-
+// A separate hasher which, by default, forwards to std::hash. This is so legacy
+// uses of BASE_HASH_NAMESPACE with base::hash_map do not interfere with
+// std::hash mid-transition.
 template<typename T>
 struct hash {
   std::size_t operator()(const T& value) const {
-    return BASE_HASH_IMPL_NAMESPACE::hash<T>()(value);
+    return std::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));
+// Deprecated. Use base::PairHash<Type1, Type2> from base/containers/pair_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::HashPair(value.first, value.second);

[danakj, 2016/01/14 21:29:10]

Can make this use PairHash? It will help with peoples' copypasta

   }
 };
 
-// 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)
-
-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>;
-
-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>;
-
-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>;
-
-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.
+// Deprecated. Use std::unordered_map instead.
 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>;
+using hash_map = std::unordered_map<Key, T, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_multimap instead.
 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>;
+using hash_multimap = std::unordered_multimap<Key, T, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_multiset instead.
 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>;
+using hash_multiset = std::unordered_multiset<Key, Hash, Pred, Alloc>;
 
+// Deprecated. Use std::unordered_set instead.
 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_t value1, uint32_t value2) {
-  uint64_t value1_64 = value1;
-  uint64_t hash64 = (value1_64 << 32) | value2;
-
-  if (sizeof(std::size_t) >= sizeof(uint64_t))
-    return static_cast<std::size_t>(hash64);
-
-  uint64_t odd_random = 481046412LL << 32 | 1025306955LL;
-  uint32_t shift_random = 10121U << 16;
-
-  hash64 = hash64 * odd_random + shift_random;
-  std::size_t high_bits = static_cast<std::size_t>(
-      hash64 >> (8 * (sizeof(uint64_t) - sizeof(std::size_t))));
-  return high_bits;
-}
-
-// Implement hashing for pairs of up-to 64-bit integer values.
-// We use the compound integer hash method to produce a 64-bit hash code, by
-// breaking the two 64-bit inputs into 4 32-bit values:
-// http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
-// Then we reduce our result to 32 bits if required, similar to above.
-inline std::size_t HashInts64(uint64_t value1, uint64_t value2) {
-  uint32_t short_random1 = 842304669U;
-  uint32_t short_random2 = 619063811U;
-  uint32_t short_random3 = 937041849U;
-  uint32_t short_random4 = 3309708029U;
-
-  uint32_t value1a = static_cast<uint32_t>(value1 & 0xffffffff);
-  uint32_t value1b = static_cast<uint32_t>((value1 >> 32) & 0xffffffff);
-  uint32_t value2a = static_cast<uint32_t>(value2 & 0xffffffff);
-  uint32_t value2b = static_cast<uint32_t>((value2 >> 32) & 0xffffffff);
-
-  uint64_t product1 = static_cast<uint64_t>(value1a) * short_random1;
-  uint64_t product2 = static_cast<uint64_t>(value1b) * short_random2;
-  uint64_t product3 = static_cast<uint64_t>(value2a) * short_random3;
-  uint64_t product4 = static_cast<uint64_t>(value2b) * short_random4;
-
-  uint64_t hash64 = product1 + product2 + product3 + product4;
-
-  if (sizeof(std::size_t) >= sizeof(uint64_t))
-    return static_cast<std::size_t>(hash64);
-
-  uint64_t odd_random = 1578233944LL << 32 | 194370989LL;
-  uint32_t shift_random = 20591U << 16;
-
-  hash64 = hash64 * odd_random + shift_random;
-  std::size_t high_bits = static_cast<std::size_t>(
-      hash64 >> (8 * (sizeof(uint64_t) - sizeof(std::size_t))));
-  return high_bits;
-}
-
-template<typename T1, typename T2>
-inline std::size_t HashPair(T1 value1, T2 value2) {
-  // This condition is expected to be compile-time evaluated and optimised away
-  // in release builds.
-  if (sizeof(T1) > sizeof(uint32_t) || (sizeof(T2) > sizeof(uint32_t)))
-    return HashInts64(value1, value2);
-
-  return HashInts32(value1, value2);
-}
+using hash_set = std::unordered_set<Key, Hash, Pred, Alloc>;
 
 }  // namespace base
 
-namespace BASE_HASH_NAMESPACE {
-
-// Implement methods for hashing a pair of integers, so they can be used as
-// keys in STL containers.
-
-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_