--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/JavaScriptCore/runtime/CachedTranscendentalFunction.h	Fri Sep 17 09:02:29 2010 +0300
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2010 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 CachedTranscendentalFunction_h
+#define CachedTranscendentalFunction_h
+
+#include "JSValue.h"
+
+namespace JSC {
+
+extern const double NaN;
+
+typedef double (*TranscendentalFunctionPtr)(double);
+
+// CachedTranscendentalFunction provides a generic mechanism to cache results
+// for pure functions with the signature "double func(double)", and where NaN
+// maps to NaN.
+template<TranscendentalFunctionPtr orignalFunction>
+class CachedTranscendentalFunction {
+    struct CacheEntry {
+        double operand;
+        double result;
+    };
+
+public:
+    CachedTranscendentalFunction()
+        : m_cache(0)
+    {
+    }
+
+    ~CachedTranscendentalFunction()
+    {
+        if (m_cache)
+            fastFree(m_cache);
+    }
+
+    JSValue operator() (ExecState* exec, double operand)
+    {
+        if (UNLIKELY(!m_cache))
+            initialize();
+        CacheEntry* entry = &m_cache[hash(operand)];
+
+        if (entry->operand == operand)
+            return jsDoubleNumber(exec, entry->result);
+        double result = orignalFunction(operand);
+        entry->operand = operand;
+        entry->result = result;
+        return jsDoubleNumber(exec, result);
+    }
+
+private:
+    void initialize()
+    {
+        // Lazily allocate the table, populate with NaN->NaN mapping.
+        m_cache = static_cast<CacheEntry*>(fastMalloc(s_cacheSize * sizeof(CacheEntry)));
+        for (unsigned x = 0; x < s_cacheSize; ++x) {
+            m_cache[x].operand = NaN;
+            m_cache[x].result = NaN;
+        }
+    }
+
+    static unsigned hash(double d)
+    {
+        union doubleAndUInt64 {
+            double d;
+            uint32_t is[2];
+        } u;
+        u.d = d;
+
+        unsigned x = u.is[0] ^ u.is[1];
+        x = (x >> 20) ^ (x >> 8);
+        return x & (s_cacheSize - 1);
+    }
+
+    static const unsigned s_cacheSize = 0x1000;
+    CacheEntry* m_cache;
+};
+
+}
+
+#endif // CachedTranscendentalFunction_h