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diff --git a/Source/JavaScriptCore/bytecode/CodeBlockHash.h b/Source/JavaScriptCore/bytecode/CodeBlockHash.h
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+/*
+ * Copyright (C) 2012 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#ifndef CodeBlockHash_h
+#define CodeBlockHash_h
+
+#include "CodeSpecializationKind.h"
+#include <wtf/PrintStream.h>
+
+// CodeBlock hashes are useful for informally identifying code blocks. They correspond
+// to the low 32 bits of a SHA1 hash of the source code with two low bit flipped
+// according to the role that the code block serves (call, construct). Additionally, the
+// hashes are typically operated over using a string in which the hash is transformed
+// into a 6-byte alphanumeric representation. This can be retrieved by using
+// toString(const CodeBlockHash&). Finally, we support CodeBlockHashes for native
+// functions, in which case the hash is replaced by the function address.
+
+namespace JSC {
+
+class SourceCode;
+
+class CodeBlockHash {
+public:
+    CodeBlockHash()
+        : m_hash(0)
+    {
+    }
+    
+    explicit CodeBlockHash(unsigned hash)
+        : m_hash(hash)
+    {
+    }
+    
+    CodeBlockHash(const SourceCode&, CodeSpecializationKind);
+    
+    explicit CodeBlockHash(const char*);
+
+    bool isSet() const { return !!m_hash; }
+    bool operator!() const { return !isSet(); }
+    
+    unsigned hash() const { return m_hash; }
+    
+    void dump(PrintStream&) const;
+    
+    // Comparison methods useful for bisection.
+    bool operator==(const CodeBlockHash& other) const { return hash() == other.hash(); }
+    bool operator!=(const CodeBlockHash& other) const { return hash() != other.hash(); }
+    bool operator<(const CodeBlockHash& other) const { return hash() < other.hash(); }
+    bool operator>(const CodeBlockHash& other) const { return hash() > other.hash(); }
+    bool operator<=(const CodeBlockHash& other) const { return hash() <= other.hash(); }
+    bool operator>=(const CodeBlockHash& other) const { return hash() >= other.hash(); }
+    
+private:
+    unsigned m_hash;
+};
+
+} // namespace JSC
+
+#endif // CodeBlockHash_h