JavaScriptCore-903.tar.gz

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

diff --git a/wtf/StackBounds.h b/wtf/StackBounds.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 COMPUTER, 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 COMPUTER, 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 StackBounds_h
+#define StackBounds_h
+
+namespace WTF {
+
+class StackBounds {
+    // recursionCheck() / recursionLimit() tests (by default)
+    // that we are at least this far from the end of the stack.
+    const static size_t s_defaultAvailabilityDelta = 4096;
+
+public:
+    StackBounds()
+        : m_origin(0)
+        , m_bound(0)
+    {
+    }
+
+    static StackBounds currentThreadStackBounds()
+    {
+        StackBounds bounds;
+        bounds.initialize();
+        bounds.checkConsistency();
+        return bounds;
+    }
+
+    void* origin() const
+    {
+        ASSERT(m_origin);
+        return m_origin;
+    }
+
+    void* current() const
+    {
+        checkConsistency();
+        void* currentPosition = &currentPosition;
+        return currentPosition;
+    }
+
+    void* recursionLimit(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
+    {
+        checkConsistency();
+        return isGrowingDownward()
+            ? static_cast<char*>(m_bound) + minAvailableDelta
+            : static_cast<char*>(m_bound) - minAvailableDelta;
+    }
+
+    bool recursionCheck(size_t minAvailableDelta = s_defaultAvailabilityDelta) const
+    {
+        checkConsistency();
+        return isGrowingDownward()
+            ? current() >= recursionLimit(minAvailableDelta)
+            : current() <= recursionLimit(minAvailableDelta);
+    }
+
+private:
+    void initialize();
+
+
+    bool isGrowingDownward() const
+    {
+        ASSERT(m_origin && m_bound);
+#if OS(WINCE)
+        return m_origin > m_bound;
+#else
+        return true;
+#endif
+    }
+
+    void checkConsistency() const;
+
+    void* m_origin;
+    void* m_bound;
+};
+
+} // namespace WTF
+
+using WTF::StackBounds;
+
+#endif