JavaScriptCore-1218.tar.gz

[apple/javascriptcore.git] / runtime / IndexingHeader.h

diff --git a/runtime/IndexingHeader.h b/runtime/IndexingHeader.h
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+/*
+ * Copyright (C) 2012 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. ``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
+ * 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 IndexingHeader_h
+#define IndexingHeader_h
+
+#include "PropertyStorage.h"
+#include <wtf/Platform.h>
+
+namespace JSC {
+
+class Butterfly;
+class LLIntOffsetsExtractor;
+class Structure;
+struct ArrayStorage;
+
+class IndexingHeader {
+public:
+    // Define the maximum storage vector length to be 2^32 / sizeof(JSValue) / 2 to ensure that
+    // there is no risk of overflow.
+    enum { maximumLength = 0x10000000 };
+    
+    static ptrdiff_t offsetOfIndexingHeader() { return -static_cast<ptrdiff_t>(sizeof(IndexingHeader)); }
+    
+    static ptrdiff_t offsetOfPublicLength() { return OBJECT_OFFSETOF(IndexingHeader, m_publicLength); }
+    static ptrdiff_t offsetOfVectorLength() { return OBJECT_OFFSETOF(IndexingHeader, m_vectorLength); }
+    
+    IndexingHeader()
+        : m_publicLength(0)
+        , m_vectorLength(0)
+    {
+    }
+    
+    uint32_t vectorLength() const { return m_vectorLength; }
+    
+    void setVectorLength(uint32_t length)
+    {
+        RELEASE_ASSERT(length <= maximumLength);
+        m_vectorLength = length;
+    }
+    
+    uint32_t publicLength() { return m_publicLength; }
+    void setPublicLength(uint32_t auxWord) { m_publicLength = auxWord; }
+    
+    static IndexingHeader* from(Butterfly* butterfly)
+    {
+        return reinterpret_cast<IndexingHeader*>(butterfly) - 1;
+    }
+    
+    static const IndexingHeader* from(const Butterfly* butterfly)
+    {
+        return reinterpret_cast<const IndexingHeader*>(butterfly) - 1;
+    }
+    
+    static IndexingHeader* from(ArrayStorage* arrayStorage)
+    {
+        return reinterpret_cast<IndexingHeader*>(arrayStorage) - 1;
+    }
+    
+    static IndexingHeader* fromEndOf(PropertyStorage propertyStorage)
+    {
+        return reinterpret_cast<IndexingHeader*>(propertyStorage);
+    }
+    
+    PropertyStorage propertyStorage()
+    {
+        return reinterpret_cast_ptr<PropertyStorage>(this);
+    }
+    
+    ConstPropertyStorage propertyStorage() const
+    {
+        return reinterpret_cast_ptr<ConstPropertyStorage>(this);
+    }
+    
+    ArrayStorage* arrayStorage()
+    {
+        return reinterpret_cast<ArrayStorage*>(this + 1);
+    }
+    
+    Butterfly* butterfly()
+    {
+        return reinterpret_cast<Butterfly*>(this + 1);
+    }
+    
+    // These methods are not standalone in the sense that they cannot be
+    // used on a copy of the IndexingHeader.
+    size_t preCapacity(Structure*);
+    size_t indexingPayloadSizeInBytes(Structure*);
+    
+private:
+    friend class LLIntOffsetsExtractor;
+    
+    uint32_t m_publicLength; // The meaning of this field depends on the array type, but for all JSArrays we rely on this being the publicly visible length (array.length).
+    uint32_t m_vectorLength; // The length of the indexed property storage. The actual size of the storage depends on this, and the type.
+};
+
+} // namespace JSC
+
+#endif // IndexingHeader_h
+