/*

 * Copyright (C) 2009 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 LinkBuffer_h

#define LinkBuffer_h

#if ENABLE(ASSEMBLER)

#include <MacroAssembler.h>

#include <wtf/Noncopyable.h>

namespace JSC {

// LinkBuffer:

//

// This class assists in linking code generated by the macro assembler, once code generation

// has been completed, and the code has been copied to is final location in memory.  At this

// time pointers to labels within the code may be resolved, and relative offsets to external

// addresses may be fixed.

//

// Specifically:

//   * Jump objects may be linked to external targets,

//   * The address of Jump objects may taken, such that it can later be relinked.

//   * The return address of a Call may be acquired.

//   * The address of a Label pointing into the code may be resolved.

//   * The value referenced by a DataLabel may be set.

//

class LinkBuffer : public Noncopyable {

    typedef MacroAssemblerCodeRef CodeRef;

    typedef MacroAssembler::Label Label;

    typedef MacroAssembler::Jump Jump;

    typedef MacroAssembler::JumpList JumpList;

    typedef MacroAssembler::Call Call;

    typedef MacroAssembler::DataLabel32 DataLabel32;

    typedef MacroAssembler::DataLabelPtr DataLabelPtr;

public:

    // Note: Initialization sequence is significant, since executablePool is a PassRefPtr.

    //       First, executablePool is copied into m_executablePool, then the initialization of

    //       m_code uses m_executablePool, *not* executablePool, since this is no longer valid.

    LinkBuffer(MacroAssembler* masm, PassRefPtr<ExecutablePool> executablePool)

        : m_executablePool(executablePool)

        , m_code(masm->m_assembler.executableCopy(m_executablePool.get()))

        , m_size(masm->m_assembler.size())

#ifndef NDEBUG

        , m_completed(false)

#endif

    {

    }

    ~LinkBuffer()

    {

        ASSERT(m_completed);

    }

    // These methods are used to link or set values at code generation time.

    void link(Call call, FunctionPtr function)

    {

        ASSERT(call.isFlagSet(Call::Linkable));

        MacroAssembler::linkCall(code(), call, function);

    }

    void link(Jump jump, CodeLocationLabel label)

    {

        MacroAssembler::linkJump(code(), jump, label);

    }

    void link(JumpList list, CodeLocationLabel label)

    {

        for (unsigned i = 0; i < list.m_jumps.size(); ++i)

            MacroAssembler::linkJump(code(), list.m_jumps[i], label);

    }

    void patch(DataLabelPtr label, void* value)

    {

        MacroAssembler::linkPointer(code(), label.m_label, value);

    }

    void patch(DataLabelPtr label, CodeLocationLabel value)

    {

        MacroAssembler::linkPointer(code(), label.m_label, value.executableAddress());

    }

    // These methods are used to obtain handles to allow the code to be relinked / repatched later.

    CodeLocationCall locationOf(Call call)

    {

        ASSERT(call.isFlagSet(Call::Linkable));

        ASSERT(!call.isFlagSet(Call::Near));

        return CodeLocationCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));

    }

    CodeLocationNearCall locationOfNearCall(Call call)

    {

        ASSERT(call.isFlagSet(Call::Linkable));

        ASSERT(call.isFlagSet(Call::Near));

        return CodeLocationNearCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));

    }

    CodeLocationLabel locationOf(Label label)

    {

        return CodeLocationLabel(MacroAssembler::getLinkerAddress(code(), label.m_label));

    }

    CodeLocationDataLabelPtr locationOf(DataLabelPtr label)

    {

        return CodeLocationDataLabelPtr(MacroAssembler::getLinkerAddress(code(), label.m_label));

    }

    CodeLocationDataLabel32 locationOf(DataLabel32 label)

    {

        return CodeLocationDataLabel32(MacroAssembler::getLinkerAddress(code(), label.m_label));

    }

    // This method obtains the return address of the call, given as an offset from

    // the start of the code.

    unsigned returnAddressOffset(Call call)

    {

        return MacroAssembler::getLinkerCallReturnOffset(call);

    }

    // Upon completion of all patching either 'finalizeCode()' or 'finalizeCodeAddendum()' should be called

    // once to complete generation of the code.  'finalizeCode()' is suited to situations

    // where the executable pool must also be retained, the lighter-weight 'finalizeCodeAddendum()' is

    // suited to adding to an existing allocation.

    CodeRef finalizeCode()

    {

        performFinalization();

        return CodeRef(m_code, m_executablePool, m_size);

    }

    CodeLocationLabel finalizeCodeAddendum()

    {

        performFinalization();

        return CodeLocationLabel(code());

    }

private:

    // Keep this private! - the underlying code should only be obtained externally via 

    // finalizeCode() or finalizeCodeAddendum().

    void* code()

    {

        return m_code;

    }

    void performFinalization()

    {

#ifndef NDEBUG

        ASSERT(!m_completed);

        m_completed = true;

#endif

        ExecutableAllocator::makeExecutable(code(), m_size);

        ExecutableAllocator::cacheFlush(code(), m_size);

    }

    RefPtr<ExecutablePool> m_executablePool;

    void* m_code;

    size_t m_size;

#ifndef NDEBUG

    bool m_completed;

#endif

};

} // namespace JSC

#endif // ENABLE(ASSEMBLER)

#endif // LinkBuffer_h