Revert of 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 54bf98b499bbce1a0f248408ac954f0f1930d7b8..c421dddf3e7c707beb1c57d72865a32376f6d9db 100644
--- a/base/containers/hash_tables.h
+++ b/base/containers/hash_tables.h
@@ -1,75 +1,281 @@
 // 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 <cstddef>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <utility>
+
+#include "base/strings/string16.h"
+#include "build/build_config.h"
+
+#if defined(COMPILER_MSVC)
 #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
-
-// Use a custom hasher instead.
+
+#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 {
 
-// 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.
+// 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 std::hash<T>()(value);
+    return BASE_HASH_IMPL_NAMESPACE::hash<T>()(value);
   }
 };
 
-// Use base::IntPairHash from base/hash.h as a custom hasher instead.
+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)
+
+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.
+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_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);
+}
+
+}  // 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::HashInts(value.first, value.second);
+    return base::HashPair(value.first, value.second);
   }
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
-namespace base {
-
-// 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 = std::unordered_map<Key, T, Hash, Pred, Alloc>;
-
-// 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 = std::unordered_multimap<Key, T, Hash, Pred, Alloc>;
-
-// 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 = std::unordered_multiset<Key, Hash, Pred, Alloc>;
-
-// 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 = std::unordered_set<Key, Hash, Pred, Alloc>;
-
-}  // namespace base
+#undef DEFINE_PAIR_HASH_FUNCTION_START
+#undef DEFINE_PAIR_HASH_FUNCTION_END
 
 #endif  // BASE_CONTAINERS_HASH_TABLES_H_