text: /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include "map.h"
  #include <errno.h>
  
  
  static DWORD get_page_size(void)
  {
  	static DWORD page_size;
  	SYSTEM_INFO sys;
  
  	if (!page_size) {
  		GetSystemInfo(&sys);
  		page_size = sys.dwAllocationGranularity;
  	}
  
  	return page_size;
  }
  
  int p_mmap(git_map *out, size_t len, int prot, int flags, int fd, git_off_t offset)
  {
  	HANDLE fh = (HANDLE)_get_osfhandle(fd);
  	DWORD page_size = get_page_size();
  	DWORD fmap_prot = 0;
  	DWORD view_prot = 0;
  	DWORD off_low = 0;
  	DWORD off_hi = 0;
  	git_off_t page_start;
  	git_off_t page_offset;
  
  	GIT_MMAP_VALIDATE(out, len, prot, flags);
  
  	out->data = NULL;
  	out->len = 0;
  	out->fmh = NULL;
  
  	if (fh == INVALID_HANDLE_VALUE) {
  		errno = EBADF;
  		giterr_set(GITERR_OS, "Failed to mmap. Invalid handle value");
  		return -1;
  	}
  
  	if (prot & GIT_PROT_WRITE)
  		fmap_prot |= PAGE_READWRITE;
  	else if (prot & GIT_PROT_READ)
  		fmap_prot |= PAGE_READONLY;
  
  	if (prot & GIT_PROT_WRITE)
  		view_prot |= FILE_MAP_WRITE;
  	if (prot & GIT_PROT_READ)
  		view_prot |= FILE_MAP_READ;
  
  	page_start = (offset / page_size) * page_size;
  	page_offset = offset - page_start;
  
  	if (page_offset != 0) { /* offset must be multiple of page size */
  		errno = EINVAL;
  		giterr_set(GITERR_OS, "Failed to mmap. Offset must be multiple of page size");
  		return -1;
  	}
  
  	out->fmh = CreateFileMapping(fh, NULL, fmap_prot, 0, 0, NULL);
  	if (!out->fmh || out->fmh == INVALID_HANDLE_VALUE) {
  		giterr_set(GITERR_OS, "Failed to mmap. Invalid handle value");
  		out->fmh = NULL;
  		return -1;
  	}
  
  	assert(sizeof(git_off_t) == 8);
  
  	off_low = (DWORD)(page_start);
  	off_hi = (DWORD)(page_start >> 32);
  	out->data = MapViewOfFile(out->fmh, view_prot, off_hi, off_low, len);
  	if (!out->data) {
  		giterr_set(GITERR_OS, "Failed to mmap. No data written");
  		CloseHandle(out->fmh);
  		out->fmh = NULL;
  		return -1;
  	}
  	out->len = len;
  
  	return 0;
  }
  
  int p_munmap(git_map *map)
  {
  	int error = 0;
  
  	assert(map != NULL);
  
  	if (map->data) {
  		if (!UnmapViewOfFile(map->data)) {
  			giterr_set(GITERR_OS, "Failed to munmap. Could not unmap view of file");
  			error = -1;
  		}
  		map->data = NULL;
  	}
  
  	if (map->fmh) {
  		if (!CloseHandle(map->fmh)) {
  			giterr_set(GITERR_OS, "Failed to munmap. Could not close handle");
  			error = -1;
  		}
  		map->fmh = NULL;
  	}
  
  	return error;
  }
  
  
  