JavaScriptCore-903.tar.gz

[apple/javascriptcore.git] / heap / HandleStack.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. AND ITS CONTRIBUTORS ``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 ITS 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 HandleStack_h
+#define HandleStack_h
+
+#include "Assertions.h"
+#include "BlockStack.h"
+#include "Handle.h"
+
+#include <wtf/UnusedParam.h>
+
+namespace JSC {
+
+class LocalScope;
+class HeapRootVisitor;
+
+class HandleStack {
+public:
+    class Frame {
+    public:
+        HandleSlot m_next;
+        HandleSlot m_end;
+    };
+
+    HandleStack();
+    
+    void enterScope(Frame&);
+    void leaveScope(Frame&);
+
+    HandleSlot push();
+
+    void mark(HeapRootVisitor&);
+
+private:
+    void grow();
+    void zapTo(Frame&);
+    HandleSlot findFirstAfter(HandleSlot);
+
+#ifndef NDEBUG
+    size_t m_scopeDepth;
+#endif
+    BlockStack<JSValue> m_blockStack;
+    Frame m_frame;
+};
+
+inline void HandleStack::enterScope(Frame& lastFrame)
+{
+#ifndef NDEBUG
+    ++m_scopeDepth;
+#endif
+
+    lastFrame = m_frame;
+}
+
+
+
+inline void HandleStack::zapTo(Frame& lastFrame)
+{
+#ifdef NDEBUG
+    UNUSED_PARAM(lastFrame);
+#else
+    const Vector<HandleSlot>& blocks = m_blockStack.blocks();
+    
+    if (lastFrame.m_end != m_frame.m_end) { // Zapping to a frame in a different block.
+        int i = blocks.size() - 1;
+        for ( ; blocks[i] + m_blockStack.blockLength != lastFrame.m_end; --i) {
+            for (int j = m_blockStack.blockLength - 1; j >= 0; --j)
+                blocks[i][j] = JSValue();
+        }
+        
+        for (HandleSlot it = blocks[i] + m_blockStack.blockLength - 1; it != lastFrame.m_next - 1; --it)
+            *it = JSValue();
+        
+        return;
+    }
+    
+    for (HandleSlot it = m_frame.m_next - 1; it != lastFrame.m_next - 1; --it)
+        *it = JSValue();
+#endif
+}
+
+inline void HandleStack::leaveScope(Frame& lastFrame)
+{
+#ifndef NDEBUG
+    --m_scopeDepth;
+#endif
+
+    zapTo(lastFrame);
+
+    if (lastFrame.m_end != m_frame.m_end) // Popping to a frame in a different block.
+        m_blockStack.shrink(lastFrame.m_end);
+
+    m_frame = lastFrame;
+}
+
+inline HandleSlot HandleStack::push()
+{
+    ASSERT(m_scopeDepth); // Creating a Local outside of a LocalScope is a memory leak.
+    if (m_frame.m_next == m_frame.m_end)
+        grow();
+    return m_frame.m_next++;
+}
+
+}
+
+#endif