1 files changed, 116 insertions, 0 deletions
diff --git a/Source/JavaScriptCore/runtime/GCHandle.h b/Source/JavaScriptCore/runtime/GCHandle.h
new file mode 100644
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+++ b/Source/JavaScriptCore/runtime/GCHandle.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 GCHandle_h
+#define GCHandle_h
+
+#include <wtf/Assertions.h>
+
+namespace JSC {
+
+class Heap;
+class JSCell;
+class WeakGCHandle;
+class WeakGCHandlePool;
+
+class WeakGCHandle {
+    friend class WeakGCHandlePool;
+
+public:
+    // Because JSCell objects are aligned, we can use the lower two bits as
+    // status flags. The least significant bit is set when the handle is not a
+    // pointer, i.e. when it's used as a offset for the free list in
+    // WeakGCHandlePool. The second least significant bit is set when the object
+    // the pointer corresponds to has been deleted by a garbage collection
+
+    bool isValidPtr() { return !(m_ptr & 3); }
+    bool isPtr() { return !(m_ptr & 1); }
+    bool isNext() { return (m_ptr & 3) == 1; }
+
+    void invalidate()
+    {
+        ASSERT(isValidPtr());
+        m_ptr |= 2;
+    }
+
+    JSCell* get()
+    {
+        ASSERT(isPtr());
+        return reinterpret_cast<JSCell*>(m_ptr & ~3);
+    }
+
+    void set(JSCell* p)
+    {
+        m_ptr = reinterpret_cast<uintptr_t>(p);
+        ASSERT(isPtr());
+    }
+
+    WeakGCHandlePool* pool();
+
+private:
+    uintptr_t getNextInFreeList()
+    {
+        ASSERT(isNext());
+        return m_ptr >> 2;
+    }
+
+    void setNextInFreeList(uintptr_t n)
+    {
+        m_ptr = (n << 2) | 1;
+        ASSERT(isNext());
+    }
+
+    uintptr_t m_ptr;
+};
+
+class WeakGCHandlePool {
+public:
+    static const size_t poolSize = 32 * 1024; // 32k
+    static const size_t poolMask = ~(poolSize - 1);
+    static const size_t numPoolEntries = (poolSize - sizeof(Heap*) - 3 * sizeof(unsigned)) / sizeof(WeakGCHandle);
+
+    WeakGCHandlePool();
+
+    WeakGCHandle* allocate(JSCell* cell);
+    void free(WeakGCHandle*);
+
+    bool isFull()
+    {
+        ASSERT(m_entriesSize < WeakGCHandlePool::numPoolEntries);
+        return m_entriesSize == WeakGCHandlePool::numPoolEntries - 1;
+    }
+
+    void update();
+
+private:
+    Heap* m_heap;
+    unsigned m_entriesSize;
+    unsigned m_initialAlloc;
+
+    WeakGCHandle m_entries[WeakGCHandlePool::numPoolEntries];
+};
+
+}
+#endif