win32utils devel - Nov 2004 - Problems with DeviceIoControl()

Hi all,

Thanks to Wayne and Park, I''ve got something like this
now:

static VALUE file_set_compressed(VALUE self, VALUE
rbBool){
   HANDLE h;
   BOOL rv;   
   DWORD dwBytesReturned;
   int fn;
   USHORT inBuf = COMPRESSION_FORMAT_DEFAULT;
   
   if((rbBool != Qtrue) && (rbBool != Qfalse)){
      rb_raise(rb_eTypeError,"Argument must be true or
false");  
   }

   if(rbBool == Qfalse){
      inBuf = COMPRESSION_FORMAT_NONE;
   }
   
   fn NUM2INT(rb_funcall(self,rb_intern("fileno"),0,0));
   h = (HANDLE)_get_osfhandle(fn); // Get HANDLE based
on fileno
   
   if(h == INVALID_HANDLE_VALUE){
     
rb_raise(cFileError,ErrorDescription(GetLastError()));
   }

   rv = DeviceIoControl(
      h,
      FSCTL_SET_COMPRESSION,
      (LPVOID)inBuf,
      sizeof(inBuf),
      NULL,
      0,
      &dwBytesReturned,
      NULL
   );
   
   if(!rv){   
  
rb_raise(cFileError,ErrorDescription(GetLastError()));
   }

   return self; 
}

// Inside Init_file()
rb_define_method(rb_cFile,"compressed=",file_set_compressed,1);

# Sample program
f = File.open("temp.txt")
f.compressed = true
f.close

But, I''m still getting "access denied" or "invalid
access to memory location", depending on the open mode
flag I use.

Testing indicates that I am getting a valid HANDLE,
but that DeviceIoControl() is failing.  I can,
however, compress the file using the GUI interface.

Any ideas?

Wayne, I saw your note on using _fileno, but I don''t
think I need it here, do I?

Regards,

Dan


		
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Hi Dan,
> Wayne, I saw your note on using _fileno, but I don''t
> think I need it here, do I?
No, it doesn''t look like you need to use _fileno.  Yesterday I took a
quick
look at Ruby''s file.c code, and it looked to me that it was using a
FILE* instead of a fileno, so I thought it might be necessary to first use
_fileno to get a fileno to be able to use the function Park pointed
out.  But based on your code it looks like you directly have access to
fileno, so _fileno isn''t needed.

I''ll try to run some experiments with DeviceIoControl(), and if I
learn anything useful, I''ll let you know.

Take care,

Wayne Vucenic

Hi,
> 
> Hi all,
> 
> Thanks to Wayne and Park, I''ve got something like this
> now:
> 
..
> 
> But, I''m still getting "access denied" or "invalid
> access to memory location", depending on the open mode
> flag I use.
> 
> Testing indicates that I am getting a valid HANDLE,
> but that DeviceIoControl() is failing.  I can,
> however, compress the file using the GUI interface.
> 
> Any ideas?
> 
> Wayne, I saw your note on using _fileno, but I don''t
> think I need it here, do I?
> 
 
You have missed & before inBuf.

Here is my modified version:
---------------------------------------------------------------
static VALUE file_set_compressed(VALUE self, VALUE rbBool){
   HANDLE h;
   BOOL rv;
   DWORD dwBytesReturned;
   int fn;
   VALUE rbPath;
   USHORT inBuf = COMPRESSION_FORMAT_DEFAULT;

   if((rbBool != Qtrue) && (rbBool != Qfalse)){
      rb_raise(rb_eTypeError,"Argument must be true or false");
   }

   if(rbBool == Qfalse){
      inBuf = COMPRESSION_FORMAT_NONE;
   }

   rbPath = rb_funcall(self,rb_intern("path"),0,0);

   h = CreateFile(
                StringValuePtr(rbPath),
                FILE_READ_DATA | FILE_WRITE_DATA,
                FILE_SHARE_READ | FILE_SHARE_WRITE,
                NULL,
                OPEN_EXISTING,
                0,
                NULL
                );

   rv = DeviceIoControl(
      h,
      FSCTL_SET_COMPRESSION,
      (LPVOID)&inBuf,
      sizeof(inBuf),
      NULL,
      0,
      &dwBytesReturned,
      NULL
   );

   CloseHandle( h );

   if(!rv){
      rb_raise(cFileError,ErrorDescription(GetLastError()));
   }

   return self;
}
----------------------------------------------------------------
Regards,

Park Heesob




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