bytecode/EvalCodeCache.h

   1 /*
   2  * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef EvalCodeCache_h
  30 #define EvalCodeCache_h
  31
  32 #include "Executable.h"
  33 #include "JSGlobalObject.h"
  34 #include "SourceCode.h"
  35 #include <wtf/HashMap.h>
  36 #include <wtf/RefPtr.h>
  37 #include <wtf/text/StringHash.h>
  38
  39 namespace JSC {
  40
  41     class SlotVisitor;
  42
  43     class EvalCodeCache {
  44     public:
  45         EvalExecutable* tryGet(bool inStrictContext, const String& evalSource, JSScope* scope)
  46         {
  47             if (!inStrictContext && evalSource.length() < maxCacheableSourceLength && scope->begin()->isVariableObject())
  48                 return m_cacheMap.get(evalSource.impl()).get();
  49             return 0;
  50         }
  51
  52         EvalExecutable* getSlow(ExecState* exec, ScriptExecutable* owner, bool inStrictContext, const String& evalSource, JSScope* scope)
  53         {
  54             EvalExecutable* evalExecutable = EvalExecutable::create(exec, makeSource(evalSource), inStrictContext);
  55             if (!evalExecutable)
  56                 return 0;
  57
  58             if (!inStrictContext && evalSource.length() < maxCacheableSourceLength && scope->begin()->isVariableObject() && m_cacheMap.size() < maxCacheEntries)
  59                 m_cacheMap.set(evalSource.impl(), WriteBarrier<EvalExecutable>(exec->vm(), owner, evalExecutable));
  60
  61             return evalExecutable;
  62         }
  63
  64         bool isEmpty() const { return m_cacheMap.isEmpty(); }
  65
  66         void visitAggregate(SlotVisitor&);
  67
  68         void clear()
  69         {
  70             m_cacheMap.clear();
  71         }
  72
  73     private:
  74         static const unsigned maxCacheableSourceLength = 256;
  75         static const int maxCacheEntries = 64;
  76
  77         typedef HashMap<RefPtr<StringImpl>, WriteBarrier<EvalExecutable>> EvalCacheMap;
  78         EvalCacheMap m_cacheMap;
  79     };
  80
  81 } // namespace JSC
  82
  83 #endif // EvalCodeCache_h