JavaScriptCore-7600.1.4.9.tar.gz

[apple/javascriptcore.git] / runtime / CachedTranscendentalFunction.h

diff --git a/runtime/CachedTranscendentalFunction.h b/runtime/CachedTranscendentalFunction.h
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--- a/runtime/CachedTranscendentalFunction.h
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-/*
- * 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 "JSCJSValue.h"
-
-namespace JSC {
-
-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() (double operand)
-    {
-        if (UNLIKELY(!m_cache))
-            initialize();
-        CacheEntry* entry = &m_cache[hash(operand)];
-
-        if (entry->operand == operand)
-            return jsDoubleNumber(entry->result);
-        double result = orignalFunction(operand);
-        entry->operand = operand;
-        entry->result = result;
-        return jsDoubleNumber(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 = QNaN;
-            m_cache[x].result = QNaN;
-        }
-    }
-
-    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