heap/LocalScope.h

   1 /*
   2  * Copyright (C) 2010 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  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef LocalScope_h
  27 #define LocalScope_h
  28
  29 #include "HandleStack.h"
  30 #include "Local.h"
  31
  32 namespace JSC {
  33 /*
  34     A LocalScope is a temporary scope in which Locals are allocated. When a
  35     LocalScope goes out of scope, all the Locals created in it are destroyed.
  36
  37     LocalScope is similar in concept to NSAutoreleasePool.
  38 */
  39
  40 class JSGlobalData;
  41
  42 class LocalScope {
  43 public:
  44     explicit LocalScope(JSGlobalData&);
  45     ~LocalScope();
  46
  47     template <typename T> Local<T> release(Local<T>); // Destroys all other locals in the scope.
  48
  49 private:
  50     HandleStack* m_handleStack;
  51     HandleStack::Frame m_lastFrame;
  52 };
  53
  54 inline LocalScope::LocalScope(JSGlobalData& globalData)
  55     : m_handleStack(globalData.heap.handleStack())
  56 {
  57     m_handleStack->enterScope(m_lastFrame);
  58 }
  59
  60 inline LocalScope::~LocalScope()
  61 {
  62     m_handleStack->leaveScope(m_lastFrame);
  63 }
  64
  65 template <typename T> Local<T> LocalScope::release(Local<T> local)
  66 {
  67     typename Local<T>::ExternalType ptr = local.get();
  68
  69     m_handleStack->leaveScope(m_lastFrame);
  70     HandleSlot slot = m_handleStack->push();
  71     m_handleStack->enterScope(m_lastFrame);
  72
  73     return Local<T>(slot, ptr);
  74 }
  75
  76 }
  77
  78 #endif