/*

 * Copyright (C) 2012 David Anderson

 *

 * This file is part of JITCraft.

 *

 * JITCraft is free software: you can redistribute it and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option)

 * any later version.

 * 

 * Foobar is distributed in the hope that it will be useful, but WITHOUT ANY

 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * JITCraft. If not, see http://www.gnu.org/licenses/.

 */

// :TODO: move into utility-style include

#define WIN32_LEAN_AND_MEAN

#include <Windows.h>

#include "Platform.h"

using namespace jc;

static inline DWORD

ToProtBits(OS::Protection prot)

{

    switch (prot) {

	  case OS::Prot_ReadWrite:

        return PAGE_READWRITE;

      case OS::Prot_ReadWriteExecute:

        return PAGE_EXECUTE_READWRITE;

      default:

        assert(prot == OS::Prot_ReadExecute);

        return PAGE_EXECUTE_READ;

    }

}

Address

OS::MapMemory(size_t amount, MapMode mode, Protection prot_)

{

    DWORD prot = ToProtBits(prot_);

    DWORD type = MEM_RESERVE;

    if (mode == Map_Commit)

        type |= MEM_COMMIT;

    return (Address)VirtualAlloc(NULL, amount, type, prot);

}

bool

OS::CommitMemory(Address address, size_t amount, Protection prot_)

{

    DWORD prot = ToProtBits(prot_);

    return !!VirtualAlloc(address, amount, MEM_COMMIT, prot);

}

void

OS::UnmapMemory(Address address, size_t size)

{

    VirtualFree(address, 0, MEM_RELEASE);

}

OS::AlignableMapping

OS::MapAlignedMemory(size_t amount, size_t alignment, MapMode mode)

{

    Address addr = MapMemory(amount, mode, OS::Prot_ReadWrite);

    if (!addr)

        return AlignableMapping(NULL, alignment, 0);

    if (!IsAligned(addr, alignment)) {

        UnmapMemory(addr, amount);

        // Try to grab the next available aligned address.

        addr = AlignedBase(addr, alignment);

        addr = MapMemoryAt(addr + alignment, amount, mode, OS::Prot_ReadWrite);

        while (!addr) {

            // Try to over-allocate to get the right region. This can race

            // with other threads; we expect this to be rare. If this turns

            // out to be a problem, the API is set up such that we can just

            // return two pointers: the base, and the aligned address into

            // the over-allocated region.

            addr = MapMemory(amount + alignment, mode, OS::Prot_ReadWrite);

            if (!addr)

                return AlignableMapping(NULL, alignment, 0);

            UnmapMemory(addr, amount + alignment);

            addr = AlignedBase(addr, alignment);

            addr = MapMemoryAt(addr + alignment, amount, mode, OS::Prot_ReadWrite);

        }

    }

    return AlignableMapping(addr, alignment, amount);

}

Address

OS::MapMemoryAt(Address address, size_t amount, MapMode mode, Protection prot_)

{

    DWORD bits = ToProtBits(prot_);

    DWORD flags = MEM_RESERVE;

    if (mode == Map_Commit)

        flags |= MEM_COMMIT;

    Address x = (Address)VirtualAlloc((LPVOID)address, amount, flags, bits);

    if (!x) {

        DWORD err = GetLastError();

        return x;

    }

    return x;

}

void

OS::UnmapAlignedMemory(Address address, size_t size)

{

    OS::UnmapMemory(address, size);

}