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diff --git a/Source/JavaScriptCore/bytecode/UnlinkedInstructionStream.h b/Source/JavaScriptCore/bytecode/UnlinkedInstructionStream.h
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+++ b/Source/JavaScriptCore/bytecode/UnlinkedInstructionStream.h
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+/*
+ * Copyright (C) 2014 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 UnlinkedInstructionStream_h
+#define UnlinkedInstructionStream_h
+
+#include "UnlinkedCodeBlock.h"
+#include <wtf/RefCountedArray.h>
+
+namespace JSC {
+
+class UnlinkedInstructionStream {
+    WTF_MAKE_FAST_ALLOCATED;
+public:
+    explicit UnlinkedInstructionStream(const Vector<UnlinkedInstruction, 0, UnsafeVectorOverflow>&);
+
+    unsigned count() const { return m_instructionCount; }
+    size_t sizeInBytes() const;
+
+    class Reader {
+    public:
+        explicit Reader(const UnlinkedInstructionStream&);
+
+        const UnlinkedInstruction* next();
+        bool atEnd() const { return m_index == m_stream.m_data.size(); }
+
+    private:
+        unsigned char read8();
+        unsigned read32();
+
+        const UnlinkedInstructionStream& m_stream;
+        UnlinkedInstruction m_unpackedBuffer[16];
+        unsigned m_index;
+    };
+
+#ifndef NDEBUG
+    const RefCountedArray<UnlinkedInstruction>& unpackForDebugging() const;
+#endif
+
+private:
+    friend class Reader;
+
+#ifndef NDEBUG
+    mutable RefCountedArray<UnlinkedInstruction> m_unpackedInstructionsForDebugging;
+#endif
+
+    RefCountedArray<unsigned char> m_data;
+    unsigned m_instructionCount;
+};
+
+// Unlinked instructions are packed in a simple stream format.
+//
+// The first byte is always the opcode.
+// It's followed by an opcode-dependent number of argument values.
+// The first 3 bits of each value determines the format:
+//
+//     5-bit positive integer (1 byte total)
+//     5-bit negative integer (1 byte total)
+//     13-bit positive integer (2 bytes total)
+//     13-bit negative integer (2 bytes total)
+//     5-bit constant register index, based at 0x40000000 (1 byte total)
+//     13-bit constant register index, based at 0x40000000 (2 bytes total)
+//     32-bit raw value (5 bytes total)
+
+enum PackedValueType {
+    Positive5Bit = 0,
+    Negative5Bit,
+    Positive13Bit,
+    Negative13Bit,
+    ConstantRegister5Bit,
+    ConstantRegister13Bit,
+    Full32Bit
+};
+
+ALWAYS_INLINE UnlinkedInstructionStream::Reader::Reader(const UnlinkedInstructionStream& stream)
+    : m_stream(stream)
+    , m_index(0)
+{
+}
+
+ALWAYS_INLINE unsigned char UnlinkedInstructionStream::Reader::read8()
+{
+    return m_stream.m_data.data()[m_index++];
+}
+
+ALWAYS_INLINE unsigned UnlinkedInstructionStream::Reader::read32()
+{
+    const unsigned char* data = &m_stream.m_data.data()[m_index];
+    unsigned char type = data[0] >> 5;
+
+    switch (type) {
+    case Positive5Bit:
+        m_index++;
+        return data[0];
+    case Negative5Bit:
+        m_index++;
+        return 0xffffffe0 | data[0];
+    case Positive13Bit:
+        m_index += 2;
+        return ((data[0] & 0x1F) << 8) | data[1];
+    case Negative13Bit:
+        m_index += 2;
+        return 0xffffe000 | ((data[0] & 0x1F) << 8) | data[1];
+    case ConstantRegister5Bit:
+        m_index++;
+        return 0x40000000 | (data[0] & 0x1F);
+    case ConstantRegister13Bit:
+        m_index += 2;
+        return 0x40000000 | ((data[0] & 0x1F) << 8) | data[1];
+    default:
+        ASSERT(type == Full32Bit);
+        m_index += 5;
+        return data[1] | data[2] << 8 | data[3] << 16 | data[4] << 24;
+    }
+}
+
+ALWAYS_INLINE const UnlinkedInstruction* UnlinkedInstructionStream::Reader::next()
+{
+    m_unpackedBuffer[0].u.opcode = static_cast<OpcodeID>(read8());
+    unsigned opLength = opcodeLength(m_unpackedBuffer[0].u.opcode);
+    for (unsigned i = 1; i < opLength; ++i)
+        m_unpackedBuffer[i].u.index = read32();
+    return m_unpackedBuffer;
+}
+
+} // namespace JSC
+
+#endif // UnlinkedInstructionStream_h