/*

  * 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);

 }