Moved SuperFastHash function from base/hash.cc to base/third_party.

base/hash.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.
 
 #ifndef BASE_HASH_H_
 #define BASE_HASH_H_
 
+#include <limits>
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/logging.h"
 
 namespace base {
 
-// From http://www.azillionmonkeys.com/qed/hash.html
-// This is the hash used on WebCore/platform/stringhash
-BASE_EXPORT uint32 SuperFastHash(const char * data, int len);
+// WARNING: This hash function should not be used for any cryptographic purpose.
+BASE_EXPORT uint32 SuperFastHash(const char* data, int len);
 
+// Computes the hash of a string |key| of a given |length|. |key| does not need
+// to be null-terminated, and may contain null bytes.
+// WARNING: This hash function should not be used for any cryptographic purpose.
 inline uint32 Hash(const char* key, size_t length) {
+  if (length > std::numeric_limits<int>::max()) {
+    NOTREACHED();
+    return 0;
+  }
   return SuperFastHash(key, static_cast<int>(length));
 }
 
+// Computes the hash of a string |key|.
+// WARNING: This hash function should not be used for any cryptographic purpose.
 inline uint32 Hash(const std::string& key) {
-  if (key.empty())
-    return 0;
-  return SuperFastHash(key.data(), static_cast<int>(key.size()));
+  return Hash(key.data(), key.size());

[Matt Giuca, 2014/02/27 05:25:29]

I fixed the static_cast here too (by calling through the other overload of
Hash).

I've also removed the early-return if key.empty(). It seems redundant (since
SuperFastHash early-exits in this case anyway). More importantly, I think the
logic in SuperFastHash should not be duplicated here (what if we wanted to
change the hash of an empty string -- we'd have to change it in two places).

 }
 
 }  // namespace base
 
 #endif  // BASE_HASH_H_