🚀 go-pugleaf

Remy, my first (or was it 2nd) instinct was to look at the
VCL code implementation. But I was just zogged out ...

Thanks again Remy.




Remy Lebeau (TeamB) wrote:
> "Colin B Maharaj" <noreply@myhost.com> wrote in message 
> news:486bb9bd$1@newsgroups.borland.com...
> 
>>   if (hf == (HANDLE)0xffffffff)
> 
> Use the INVALID_HANDLE_VALUE macro instead:
> 
>     if (hf == INVALID_HANDLE_VALUE)
> 
>>      char *lpMsgBuf;
>>      FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | 
>> FORMAT_MESSAGE_FROM_SYSTEM,NULL,
>>      GetLastError(),MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),(LPTSTR) 
>> &lpMsgBuf,0,NULL);
> 
> The VCL has a SysErrorMessage() function that does that work for you:
> 
>     ShowMessage(SysErrorMessage(GetLastError()));
> 
> In any case, GetLastError() is returning ERROR_SHARING_VIOLATION (32, "The 
> process cannot access the file because it is being used by another 
> process.").  Which means your call to CreateFile() is not asking for enough 
> sharing rights to allow it to succeed.
> 
> If you take your second call to FileOpen():
> 
>     int FileHandle2 = FileOpen(A, fmOpenRead | fmShareDenyNone);
> 
> And look at how FileOpen() is implemented in SysUtils.pas (if you have the 
> VCL source code installed), you will see that it expands to the following 
> CreateFile() call:
> 
>     ... = CreateFile(FileName, GENERIC_READ, FILE_SHARE_READ | 
> FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
> 
> Notice the extra FILE_SHARE_WRITE flag?  That is the key to making your code 
> work.
> 
> Your first call to FileOpen() specifies the fmOpenReadWrite flag:
> 
>     int FileHandle = FileOpen(A, fmOpenReadWrite|fmShareDenyNone);
> 
> That expands to this:
> 
>     ... = CreateFile(FileName, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ 
> | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
> 
> Since the file is writable, any subsequent opening of the file while the 
> first handle is still active must specify the FILE_SHARE_WRITE flag or the 
> opening fails.  That is why your second call to FileOpen() succeeds but your 
> call to CreateFile() fails.
> 
> 
> Gambit 
> 
>