Once again i have a problem abusing this forum for help, sorry.

I am looking for a way to return a part of a File in a function without writing it to hdd but sending the part itself as a File.
Maybe someone has an idea how to do that?

File myfunction(...requestedPart...)
{
  File bigfile = new File(bigfilename, FileMode.In);
  ...
  bigfile.read(request, requested part);
  ...
  return request;
}

Now i want this "request" not to be a string with the content but a File-Type itself without saving it to hdd. I want it to be saved in memory only but be able to handle same like File-type. Anything like that possible?
Maybe i need to make my own class from File or something?!?
Thanks for any help!

Charma wrote:
> Once again i have a problem abusing this forum for help, sorry.

Perhaps you should just start using digitalmars.D.learn, that's what it's there for ;)...

> I am looking for a way to return a part of a File in a function without writing it to hdd but sending the part itself as a File.
> Maybe someone has an idea how to do that?
> 
> File myfunction(...requestedPart...)
> {
>   File bigfile = new File(bigfilename, FileMode.In);
>   ...
>   bigfile.read(request, requested part);
>   ...
>   return request;
> }
> 
> Now i want this "request" not to be a string with the content but a File-Type itself without saving it to hdd. I want it to be saved in memory only but be able to handle same like File-type. Anything like that possible?
> Maybe i need to make my own class from File or something?!?
> Thanks for any help!

Any particular reason you want to return it as a File if it's not, you know, a _file_?
Perhaps it'd be easier to just change the return type to Stream, and return a SliceStream? Or a MemoryStream if you insist on pre-reading the data, for example if you're paranoid about write operations changing the contents of the file while you're working with it.

Charma wrote:
> Once again i have a problem abusing this forum for help, sorry.

You might consider posting these questions to digitalmars.d.learn instead.  Then no one would have a reason to complain.

> I am looking for a way to return a part of a File in a function without writing it to hdd but sending the part itself as a File.
> Maybe someone has an idea how to do that?
> 
> File myfunction(...requestedPart...)
> {
>   File bigfile = new File(bigfilename, FileMode.In);
>   ...
>   bigfile.read(request, requested part);
>   ...
>   return request;
> }
> 
> Now i want this "request" not to be a string with the content but a File-Type itself without saving it to hdd. I want it to be saved in memory only but be able to handle same like File-type. Anything like that possible?
> Maybe i need to make my own class from File or something?!?
> Thanks for any help!

Probably you want to look at std.stream.MemoryStream.

--bb

Bill Baxter Wrote:

> Charma wrote:
> > Once again i have a problem abusing this forum for help, sorry.
> 
> You might consider posting these questions to digitalmars.d.learn instead.  Then no one would have a reason to complain.
> 
> > I am looking for a way to return a part of a File in a function without writing it to hdd but sending the part itself as a File.
> > Maybe someone has an idea how to do that?
> > 
> > File myfunction(...requestedPart...)
> > {
> >   File bigfile = new File(bigfilename, FileMode.In);
> >   ...
> >   bigfile.read(request, requested part);
> >   ...
> >   return request;
> > }
> > 
> > Now i want this "request" not to be a string with the content but a File-Type itself without saving it to hdd. I want it to be saved in memory only but be able to handle same like File-type. Anything like that possible?
> > Maybe i need to make my own class from File or something?!?
> > Thanks for any help!
> 
> Probably you want to look at std.stream.MemoryStream.
> 
> --bb


Thanks, i have tryed MemoryStream now but it looks like read(), readLine() and so on don't work anymore..

MemoryStream loadFile(char[] fname)
{
	BufferedFile load = new BufferedFile(fname, FileMode.In);
	...
	...seek(..)
	ubyte[] buff;
	buff.length = sizeOfRequestedFile;
	...
	load.read(buff);
	writefln(buff); // <-- up to here it seems to work perfectly
	...
	MemoryStream Request = new MemoryStream;
	Request.reserve(sizeOfRequestedFile);

	Request.write(buff); // here i write it into the MemoryStream

	return Request;
}


this is where i use it:

MemoryStream xy = bla.loadFile("text3.txt");

char[] asd;
while(!xy.eof())
{
	xy.readLine(asd);
	writefln("xy: ", asd);
}
i get no output for some reason... the MemoryStream seems to be empty still... but no compiler-errors... What did i do wrong?

Charma Wrote:

> Bill Baxter Wrote:
> 
> > Charma wrote:
> > > Once again i have a problem abusing this forum for help, sorry.
> > 
> > You might consider posting these questions to digitalmars.d.learn instead.  Then no one would have a reason to complain.
> > 
> > > I am looking for a way to return a part of a File in a function without writing it to hdd but sending the part itself as a File.
> > > Maybe someone has an idea how to do that?
> > > 
> > > File myfunction(...requestedPart...)
> > > {
> > >   File bigfile = new File(bigfilename, FileMode.In);
> > >   ...
> > >   bigfile.read(request, requested part);
> > >   ...
> > >   return request;
> > > }
> > > 
> > > Now i want this "request" not to be a string with the content but a File-Type itself without saving it to hdd. I want it to be saved in memory only but be able to handle same like File-type. Anything like that possible?
> > > Maybe i need to make my own class from File or something?!?
> > > Thanks for any help!
> > 
> > Probably you want to look at std.stream.MemoryStream.
> > 
> > --bb
> 
> 
> Thanks, i have tryed MemoryStream now but it looks like read(), readLine() and so on don't work anymore..
> 
> MemoryStream loadFile(char[] fname)
> {
> 	BufferedFile load = new BufferedFile(fname, FileMode.In);
> 	...
> 	...seek(..)
> 	ubyte[] buff;
> 	buff.length = sizeOfRequestedFile;
> 	...
> 	load.read(buff);
> 	writefln(buff); // <-- up to here it seems to work perfectly
> 	...
> 	MemoryStream Request = new MemoryStream;
> 	Request.reserve(sizeOfRequestedFile);
> 
> 	Request.write(buff); // here i write it into the MemoryStream
> 
> 	return Request;
> }
> 
> 
> this is where i use it:
> 
> MemoryStream xy = bla.loadFile("text3.txt");
> 
> char[] asd;
> while(!xy.eof())
> {
> 	xy.readLine(asd);
> 	writefln("xy: ", asd);
> }
> i get no output for some reason... the MemoryStream seems to be empty still... but no compiler-errors... What did i do wrong?



I'm very sorry... the stupid me forgot to seek to position 0 again before reading! Everything works perfect now! Thanks a lot!

Reply to Charma,

>> writefln(buff); // <-- up to here it seems to work perfectly
>> ...
>> MemoryStream Request = new MemoryStream;
>> Request.reserve(sizeOfRequestedFile);
>> Request.write(buff); // here i write it into the MemoryStream
>> 
>> return Request;
>> }
[...]
> I'm very sorry... the stupid me forgot to seek to position 0 again
> before reading! Everything works perfect now! Thanks a lot!
> 


option #2:

MemoryStream Request = new MemoryStream(buff);

// no seek(0) needed