🚀 go-pugleaf

"Remy Lebeau \(TeamB\)" <gambit47@yahoo.com> wrote:
>If you're conserned about speed, then memory mapping the soource file will
>be much faster then using ReadFile() for it.  By mapping the file into
>memory (CreateFileMapping() and MapViewOfFile()), you can access the file
>data directly as a simple BYTE* array, hardly any disk I/O is used at all
>(except for maybe occasional page swapping if the file is very large).  Disk
>I/O is always a bottleneck when performing data processing, so the more
>processing you can do in memory directly, the better the performance will
>be.
>

I think that file mapping is not much faster then Win32 API 
in this case. Most data on CDROM and even those that is 
located on HDD CDROM could be changes - it is source file.
So PAGE_WRITECOPY should be used like follow:

hFile = CreateFile("D:\\Software\\Drivers\\TWSWTCP\\TWSWTCP.exe", GENERIC_READ , FILE_SHARE_READ, NULL, OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL, 0);

if(hFile == INVALID_HANDLE_VALUE)
        {
         DWORD ddd=GetLastError();
         return;
        }

hFileMapping = CreateFileMapping(hFile, NULL, PAGE_WRITECOPY, 0, 0, NULL);
if(hFileMapping == 0)
        {
         CloseHandle(hFile);

         return;
        }

lpFileBase = MapViewOfFile(hFileMapping, FILE_MAP_COPY, 0, 0, 0);
if(lpFileBase == 0)
        {
         CloseHandle(hFileMapping);
         CloseHandle(hFile);

         return;
        }

Microsoft said that for PAGE_WRITECOPY are both GENERIC_READ 
and GENERIC_WRITE are needed but it is incorrect for CDROM 
(only GENERIC_READ). When PAGE_WRITECOPY will be used 
then the pages will automatically swappable after changes for 
big files (files that can't be loading as a whole). 
If file can be loadind entirely it means that it can be 
loading entirely via ReadFile API.

Vladimir.