JavaScriptCore-903.tar.gz

[apple/javascriptcore.git] / wtf / BlockStack.h

diff --git a/wtf/BlockStack.h b/wtf/BlockStack.h
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+/*
+ * Copyright (C) 2011 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 BlockStack_h
+#define BlockStack_h
+
+#include <wtf/Assertions.h>
+#include <wtf/Vector.h>
+
+namespace WTF {
+
+template <typename T> class BlockStack {
+public:
+    static const size_t blockSize = 4096;
+    static const size_t blockLength = blockSize / sizeof(T);
+
+    BlockStack();
+    ~BlockStack();
+
+    T* grow();
+    void shrink(T*);
+
+    const Vector<T*>& blocks();
+
+private:
+    Vector<T*> m_blocks;
+    T* m_spareBlock; // Used to avoid thrash at block boundaries.
+};
+
+template <typename T> BlockStack<T>::BlockStack()
+    : m_spareBlock(0)
+{
+}
+
+template <typename T> BlockStack<T>::~BlockStack()
+{
+    if (m_spareBlock)
+        free(m_spareBlock);
+    for (size_t i = 0; i < m_blocks.size(); ++i)
+        free(m_blocks[i]);
+}
+
+template <typename T> inline const Vector<T*>& BlockStack<T>::blocks()
+{
+    return m_blocks;
+}
+
+template <typename T> T* BlockStack<T>::grow()
+{
+    T* block = m_spareBlock ? m_spareBlock : static_cast<T*>(malloc(blockSize));
+    m_spareBlock = 0;
+
+    m_blocks.append(block);
+    return block;
+}
+
+template <typename T> void BlockStack<T>::shrink(T* newEnd)
+{
+    ASSERT(newEnd != m_blocks.last() + blockLength);
+    m_spareBlock = m_blocks.last();
+    m_blocks.removeLast();
+
+    while (m_blocks.last() + blockLength != newEnd) {
+        free(m_blocks.last());
+        m_blocks.removeLast();
+    }
+}
+
+}
+
+using WTF::BlockStack;
+
+#endif