//------------------------------------------------------------------------------
// Copyright (c) 2019 by contributors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//------------------------------------------------------------------------------

/* 
* mman.h for Windows
* This part is referenced from https://github.com/klauspost/mman-win32 
*/

#ifndef _SYS_MMAN_H_
#define _SYS_MMAN_H_

#pragma warning(disable : 4996)

// All the headers include this file.
#define NOMINMAX
#define WIN32_LEAN_AND_MEAN
#include <sys/types.h>
#include <windows.h>
#include <errno.h>
#include <io.h>

#define PROT_NONE       0
#define PROT_READ       1
#define PROT_WRITE      2
#define PROT_EXEC       4

#define MAP_FILE        0
#define MAP_SHARED      1
#define MAP_PRIVATE     2
#define MAP_TYPE        0xf
#define MAP_FIXED       0x10
#define MAP_ANONYMOUS   0x20
#define MAP_ANON        MAP_ANONYMOUS

#define MAP_FAILED      ((void *)-1)

// Flags for msync.
#define MS_ASYNC        1
#define MS_SYNC         2
#define MS_INVALIDATE   4

#ifndef FILE_MAP_EXECUTE
#define FILE_MAP_EXECUTE    0x0020
#endif // FILE_MAP_EXECUTE

void*   mmap(void *addr, size_t len, int prot, int flags, int fildes, off_t off);
int     munmap(void *addr, size_t len);
int     mprotect(void *addr, size_t len, int prot);
int     msync(void *addr, size_t len, int flags);
int     mlock(const void *addr, size_t len);
int     munlock(const void *addr, size_t len);


static int __map_mman_error(const DWORD err, const int deferr) {
  if (err == 0)
      return 0;
  //TODO: implement
  return err;
}

static DWORD __map_mmap_prot_page(const int prot) {
  DWORD protect = 0;
  
  if (prot == PROT_NONE)
    return protect;   
  if ((prot & PROT_EXEC) != 0) {
    protect = ((prot & PROT_WRITE) != 0) ? 
              PAGE_EXECUTE_READWRITE : PAGE_EXECUTE_READ;
  } else {
    protect = ((prot & PROT_WRITE) != 0) ?
              PAGE_READWRITE : PAGE_READONLY;
  }
  return protect;
}

static DWORD __map_mmap_prot_file(const int prot) {
  DWORD desiredAccess = 0;
    
  if (prot == PROT_NONE)
    return desiredAccess;
      
  if ((prot & PROT_READ) != 0)
    desiredAccess |= FILE_MAP_READ;
  if ((prot & PROT_WRITE) != 0)
    desiredAccess |= FILE_MAP_WRITE;
  if ((prot & PROT_EXEC) != 0)
    desiredAccess |= FILE_MAP_EXECUTE;
  return desiredAccess;
}

void* mmap(void *addr, size_t len, int prot, int flags, int fildes, off_t off) {
  HANDLE fm, h;
  
  void * map = MAP_FAILED;
  const DWORD dwFileOffsetLow = (sizeof(off_t) <= sizeof(DWORD)) ? 
                                (DWORD)off : (DWORD)(off & 0xFFFFFFFFL);
  const DWORD dwFileOffsetHigh = (sizeof(off_t) <= sizeof(DWORD)) ?
                                 (DWORD)0 : (DWORD)((off >> 32) & 0xFFFFFFFFL);
  const DWORD protect = __map_mmap_prot_page(prot);
  const DWORD desiredAccess = __map_mmap_prot_file(prot);
  const off_t maxSize = off + (off_t)len;
  const DWORD dwMaxSizeLow = (sizeof(off_t) <= sizeof(DWORD)) ? 
                             (DWORD)maxSize : (DWORD)(maxSize & 0xFFFFFFFFL);
  const DWORD dwMaxSizeHigh = (sizeof(off_t) <= sizeof(DWORD)) ?
                              (DWORD)0 : (DWORD)((maxSize >> 32) & 0xFFFFFFFFL);
  errno = 0;
  
  if (len == 0 
    // Unsupported flag combinations
    || (flags & MAP_FIXED) != 0
    // Unsupported protection combinations
    || prot == PROT_EXEC) {
    errno = EINVAL;
    return MAP_FAILED;
  }
  h = ((flags & MAP_ANONYMOUS) == 0) ? 
      (HANDLE)_get_osfhandle(fildes) : INVALID_HANDLE_VALUE;
  if ((flags & MAP_ANONYMOUS) == 0 && h == INVALID_HANDLE_VALUE) {
    errno = EBADF;
    return MAP_FAILED;
  }

  fm = CreateFileMapping(h, NULL, protect, dwMaxSizeHigh, dwMaxSizeLow, NULL);
  if (fm == NULL) {
    errno = __map_mman_error(GetLastError(), EPERM);
    return MAP_FAILED;
  }

  map = MapViewOfFile(fm, desiredAccess, dwFileOffsetHigh, dwFileOffsetLow, len);
  CloseHandle(fm);

  if (map == NULL) {
    errno = __map_mman_error(GetLastError(), EPERM);
    return MAP_FAILED;
  }
  return map;
}

int munmap(void *addr, size_t len) {
  if (UnmapViewOfFile(addr))
    return 0;
        
  errno =  __map_mman_error(GetLastError(), EPERM);
  return -1;
}

int mprotect(void *addr, size_t len, int prot) {
  DWORD newProtect = __map_mmap_prot_page(prot);
  DWORD oldProtect = 0;
  
  if (VirtualProtect(addr, len, newProtect, &oldProtect))
    return 0;
  
  errno =  __map_mman_error(GetLastError(), EPERM);
  return -1;
}

int msync(void *addr, size_t len, int flags) {
  if (FlushViewOfFile(addr, len))
    return 0;
  
  errno =  __map_mman_error(GetLastError(), EPERM);
  return -1;
}

int mlock(const void *addr, size_t len) {
  if (VirtualLock((LPVOID)addr, len))
    return 0;
      
  errno =  __map_mman_error(GetLastError(), EPERM);
  return -1;
}

int munlock(const void *addr, size_t len) {
  if (VirtualUnlock((LPVOID)addr, len))
    return 0;
      
  errno =  __map_mman_error(GetLastError(), EPERM);
  return -1;
}

#endif //  _SYS_MMAN_H_
