thodg/libgit2/src/win32/map.c

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• Hash : f7310540
  Author :
  Date : 2014-05-13T02:41:48
  

  indexer: use mmap for writing
  
  Some OSs cannot keep their ideas about file content straight when mixing
  standard IO with file mapping. As we use mmap for reading from the
  packfile, let's make writing to the pack file use mmap.
  

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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.dwAllocationGranularity;
  	}
  
  	return page_size;
  }
  
  long git__page_size(void)
  {
  	return (long)get_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;
  }
  
  #endif
  

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