Memory file ing API Test

Address: http://www.cnblogs.com/yejiansnake/archive/2010/11/24/FileMapping.html

Code

1 # include <windows. h>
2
3 void main ()
4 {
5 handle hfile = createfile (
6 "G: \ test.txt", // file name
7 generic_read | generic_write, // read and write the file
8 file_pai_read | file_pai_write,
9 null,
10 create_always, // open an existing file
11 file_attribute_normal,
12 0 );
13
14 handle hmapfile = createfilemapping (
15 hfile,
16 null,
17 page_readwrite, // read and write the ing File
18 2,
19 935*1024*1024 + 64*1024, // these two parameters are 64-bit in total, so the maximum file length supported is 16 EB.
20 null );
21
22 if (hmapfile = invalid_handle_value)
23 {
24 closehandle (hfile );
25 return;
26}
27
28 // map the file data to the address space of the process
29 void * pvfile = mapviewoffile (
30 hmapfile,
31 file_map_read | file_map_write,
32 2,
33 64*1024,
34 0 );
35
36 DWORD dwerror = getlasterror ();
37
38 If (pvfile)
39 {
40 unsigned char * P = (unsigned char *) pvfile;
41
42 p [1] = 52;
43
44 // end
45 unmapviewoffile (pvfile); // undo the ing
46}
47
48 closehandle (hmapfile); // close the file
49 closehandle (hfile); // close the file
50}
51

Conclusion:

1. createfilemapping can open many large files. After the call, the file size is allocated.

2. Two mapviewoffile Parameters
DWORD DwfileoffsethighAnd DWORD
Dwfileoffsetlow
All must be an integer multiple of 64 KB, and the parametersSize_t

DwnumberofbytestomapThe parameter indicates the number of bytes mapped to the memory. The value depends on the actual machine memory size. If the value is 0, the function will map the offset to the space at the end of the file by default, an error occurs when the file size is too large due to insufficient memory.

3. 2 GB memory of the Local Machine. 922 MB has been used, and the maximum ing size is only 935 MB.