Hashing string16s.

base/hash_tables.h

 // Copyright (c) 2006-2008 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;
 //
 
 #ifndef BASE_HASH_TABLES_H__
 #define BASE_HASH_TABLES_H__
 
 #include "build/build_config.h"
 
+#include "base/string16.h"
+
 #if defined(COMPILER_MSVC)
 #include <hash_map>
 #include <hash_set>
 namespace base {
 using stdext::hash_map;
 using stdext::hash_set;
 }
 #elif defined(COMPILER_GCC)
 // 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
@@ skipping 63 matching lines @@
   }
 };
 
 template<>
 struct hash<long long> {
   size_t operator()(long long i) const {
     return std::tr1::hash<long>()((long) i);
   }
 };
 
+#if defined(WCHAR_T_IS_UTF32)
+template<>
+struct hash<string16> {
+  size_t operator()(const string16& s) const {
+    // This comes from GNU libstdc++, but the types have been changed to
+    // make it compile.  The lib only defines the hash for string and wstring.
+    std::size_t result = 0;
+    for (string16::const_iterator i = s.begin(); i != s.end(); ++i)
+      result = (result * 131) + *i;
+    return result;
+  }
+};
+
+template<>
+struct hash<const string16> {
+  size_t operator()(const string16& s) const {
+    // This comes from GNU libstdc++, but the types have been changed to
+    // make it compile.  The lib only defines the hash for string and wstring.
+    std::size_t result = 0;
+    for (string16::const_iterator i = s.begin(); i != s.end(); ++i)
+      result = (result * 131) + *i;
+    return result;
+  }
+};
+#endif
+
 }
 
 #endif
 
 #endif  // BASE_HASH_TABLES_H__