thodg/libgit2/src/win32/map.c

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• Hash : d8fcafb2
  Author :
  Date : 2016-03-16T19:05:11
  

  Split the page size from the mmap alignment While often similar, these are not the same on Windows. We want to use the page size on Windows for the pools, but for mmap we need to use the allocation granularity as the alignment. On the other platforms these values remain the same.

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• src/win32/map.c

• /*
   * 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>
  
  #ifndef NO_MMAP
  
  static DWORD get_page_size(void)
  {
  	static DWORD page_size;
  	SYSTEM_INFO sys;
  
  	if (!page_size) {
  		GetSystemInfo(&sys);
  		page_size = sys.dwPageSize;
  	}
  
  	return page_size;
  }
  
  static DWORD get_allocation_granularity(void)
  {
  	static DWORD granularity;
  	SYSTEM_INFO sys;
  
  	if (!granularity) {
  		GetSystemInfo(&sys);
  		granularity = sys.dwAllocationGranularity;
  	}
  
  	return granularity;
  }
  
  int git__page_size(size_t *page_size)
  {
  	*page_size = get_page_size();
  	return 0;
  }
  
  int git__mmap_alignment(size_t *page_size)
  {
  	*page_size = get_allocation_granularity();
  	return 0;
  }
  
  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 alignment = get_allocation_granularity();
  	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 / alignment) * alignment;
  	page_offset = offset - page_start;
  
  	if (page_offset != 0) { /* offset must be multiple of the allocation granularity */
  		errno = EINVAL;
  		giterr_set(GITERR_OS, "Failed to mmap. Offset must be multiple of allocation granularity");
  		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;
  }
  
  #endif
  

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