/* vim: set ts=4 sw=4 tw=99 et:
 *
 * Copyright (C) 2012 David Anderson
 *
 * This file is part of SourcePawn.
 *
 * SourcePawn 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.
 * 
 * SourcePawn 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
 * SourcePawn. 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 ke;

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);
}

static Address
MapMemoryAt(Address address, size_t amount, OS::MapMode mode, OS::Protection prot_)
{
    DWORD bits = ToProtBits(prot_);
    DWORD flags = MEM_RESERVE;
    if (mode == OS::Map_Commit)
        flags |= MEM_COMMIT;

    return (Address)VirtualAlloc((LPVOID)address, amount, flags, bits);
}

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);
}

void
OS::UnmapAlignedMemory(Address address, size_t size)
{
    OS::UnmapMemory(address, size);
}