X-Git-Url: https://git.saurik.com/apple/javascriptcore.git/blobdiff_plain/a253471d7f8e4d91bf6ebabab00155c3b387d3d0..93a3786624b2768d89bfa27e46598dc64e2fb70a:/runtime/ArrayStorage.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 ArrayStorage_h
+#define ArrayStorage_h
+
+#include "ArrayConventions.h"
+#include "Butterfly.h"
+#include "IndexingHeader.h"
+#include "SparseArrayValueMap.h"
+#include "WriteBarrier.h"
+#include <wtf/Noncopyable.h>
+#include <wtf/Platform.h>
+
+namespace JSC {
+
+// This struct holds the actual data values of an array. A JSArray object points to its contained ArrayStorage
+// struct by pointing to m_vector. To access the contained ArrayStorage struct, use the getStorage() and 
+// setStorage() methods. It is important to note that there may be space before the ArrayStorage that 
+// is used to quick unshift / shift operation. The actual allocated pointer is available by using:
+//     getStorage() - m_indexBias * sizeof(JSValue)
+// All slots in ArrayStorage (slots from 0 to vectorLength) are expected to be initialized to a JSValue or,
+// for hole slots, JSValue().
+struct ArrayStorage {
+    WTF_MAKE_NONCOPYABLE(ArrayStorage);
+private:
+    ArrayStorage() { } // Not directly instantiable. Can only be created as part of a Butterfly.
+public:
+    
+    static ArrayStorage* from(Butterfly* butterfly) { return reinterpret_cast_ptr<ArrayStorage*>(butterfly); }
+    static ArrayStorage* from(IndexingHeader* indexingHeader) { return indexingHeader->arrayStorage(); }
+    
+    Butterfly* butterfly() { return reinterpret_cast<Butterfly*>(this); }
+    IndexingHeader* indexingHeader() { return IndexingHeader::from(this); }
+    
+    // We steal two fields from the indexing header: vectorLength and length.
+    unsigned length() { return indexingHeader()->publicLength(); }
+    void setLength(unsigned length) { indexingHeader()->setPublicLength(length); }
+    unsigned vectorLength() { return indexingHeader()->vectorLength(); }
+    void setVectorLength(unsigned length) { indexingHeader()->setVectorLength(length); }
+    
+    ALWAYS_INLINE void copyHeaderFromDuringGC(const ArrayStorage& other)
+    {
+        m_sparseMap.copyFrom(other.m_sparseMap);
+        m_indexBias = other.m_indexBias;
+        m_numValuesInVector = other.m_numValuesInVector;
+    }
+    
+    bool inSparseMode()
+    {
+        return m_sparseMap && m_sparseMap->sparseMode();
+    }
+
+    ContiguousJSValues vector() { return ContiguousJSValues(m_vector, vectorLength()); }
+
+    WriteBarrier<SparseArrayValueMap> m_sparseMap;
+    unsigned m_indexBias;
+    unsigned m_numValuesInVector;
+#if USE(JSVALUE32_64)
+    uintptr_t m_padding;
+#endif
+    WriteBarrier<Unknown> m_vector[1];
+    
+    static ptrdiff_t lengthOffset() { return Butterfly::offsetOfPublicLength(); }
+    static ptrdiff_t vectorLengthOffset() { return Butterfly::offsetOfVectorLength(); }
+    static ptrdiff_t numValuesInVectorOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_numValuesInVector); }
+    static ptrdiff_t vectorOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_vector); }
+    static ptrdiff_t indexBiasOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_indexBias); }
+    static ptrdiff_t sparseMapOffset() { return OBJECT_OFFSETOF(ArrayStorage, m_sparseMap); }
+    
+    static size_t sizeFor(unsigned vectorLength)
+    {
+        return ArrayStorage::vectorOffset() + vectorLength * sizeof(WriteBarrier<Unknown>);
+    }
+};
+
+} // namespace JSC
+
+#endif // ArrayStorage_h
+