From 2a4e5fbb838517d03c760974ccc6a2ff8939dd08 Mon Sep 17 00:00:00 2001
From: "pinkerton@google.com"
 <pinkerton@google.com@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Mon, 4 Aug 2008 18:36:53 +0000
Subject: Adding specializations of hash() for various string types. GCC
 requires you bring your own hash function for maps and sets. Review URL:
 http://chrome-reviews.prom.corp.google.com/1085

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@327 0039d316-1c4b-4281-b951-d872f2087c98
---
 base/hash_tables.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 66 insertions(+), 5 deletions(-)

(limited to 'base')

diff --git a/base/hash_tables.h b/base/hash_tables.h
index 13c201b..10539d7 100644
--- a/base/hash_tables.h
+++ b/base/hash_tables.h
@@ -27,8 +27,14 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
+
+//
 // Deal with the differences between Microsoft and GNU implemenations
-// of hash_map
+// 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__
@@ -38,15 +44,70 @@
 #include <hash_map>
 #include <hash_set>
 namespace base {
-  using stdext::hash_map;
-  using stdext::hash_set;
+using stdext::hash_map;
+using stdext::hash_set;
 }
 #else
 #include <ext/hash_map>
 #include <ext/hash_set>
 namespace base {
-  using __gnu_cxx::hash_map;
-  using __gnu_cxx::hash_set;
+using __gnu_cxx::hash_map;
+using __gnu_cxx::hash_set;
+}
+
+// Implement string hash functions so that strings of various flavors can
+// be used as keys in STL maps and sets.
+namespace __gnu_cxx {
+
+inline size_t stl_hash_wstring(const wchar_t* s) {
+  unsigned long h = 0;
+  for ( ; *s; ++s)
+    h = 5 * h + *s;
+  return size_t(h);
+}
+
+template<>
+struct hash<wchar_t*> {
+  size_t operator()(const wchar_t* s) const {
+    return stl_hash_wstring(s); 
+  }
+};
+
+template<>
+struct hash<const wchar_t*> {
+  size_t operator()(const wchar_t* s) const {
+    return stl_hash_wstring(s); 
+  }
+};
+
+template<>
+struct hash<std::wstring> {
+  size_t operator()(const std::wstring& s) const {
+    return stl_hash_wstring(s.c_str()); 
+  }
+};
+
+template<>
+struct hash<const std::wstring> {
+  size_t operator()(const std::wstring& s) const {
+    return stl_hash_wstring(s.c_str());
+  }
+};
+
+template<>
+struct hash<std::string> {
+  size_t operator()(const std::string& s) const {
+    return __stl_hash_string(s.c_str());
+  }
+};
+
+template<>
+struct hash<const std::string> {
+  size_t operator()(const std::string& s) const {
+    return __stl_hash_string(s.c_str());
+  }
+};  
+
 }
 
 #endif
-- 
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