[fpc-pascal]TFileStream

[Full_Name]

Quoting Michael Van Canneyt <michael.vancanneyt at wisa.be>:

If TFileStream is the same as Delphi's class, the following should work:

WRITE:

var
  fs: TFileStream;
  teststr: string;
  i: integer;
begin
  teststr := 'THIS IS A TEST STRING';

  fs := TFileStream.Create('c:\out\text.txt', fmCreate);
  try
    for i := 1 to length(teststr) do
      fs.Write(teststr[i], sizeof(char));
  finally
    fs.free;
  end;
end;

READ:

var
  fs: TFileStream;
  teststr: string;
  a: char;
  i: integer;
begin
  teststr := '';

  fs := TFileStream.Create('c:\out\text.txt', fmOpenRead);
  try
    fs.Position := 0;
    for i := 1 to fs.size do begin
      fs.Read(a, sizeof(char));
      teststr := teststr + a;
    end;
  finally
    fs.free;
  end;

  writeln(teststr);
end;

These examples are a bit cheesey (not how I would personally do things), but 
they are taken from an example I knocked up for a delegate on a course I taught 
a while back. He wanted a simple example of how to read and write to files. 

Using this basic template, you could change 'char' for any type (word, integer, 
record etc).. Strings are tricky, as Delphi does some clever stuff behind the 
scenes, but FPC might allow them to be used directly.

open(stream)
while not(eof(stream))
 packet=read(stream,size) <-- read a record of fixed length
 parse(packet)
end
close(stream)

could be translated as (untested):

var
  fs: TFileStream;
  aPacket: TPacket; //defined as whatever you like else where
  i: integer;
begin
  teststr := '';

  fs := TFileStream.Create('c:\filetoread.ext', fmOpenRead); //opens stream
  try
    fs.Position := 0; //make double sure at start.. delphi doesn't
                      //open at position '0'... not always, anyway...

    {may want a check to make sure there's enough file left to read..
     otherwise this may fail/never exit... } 
    while (fs.position < fs.size) {NB ^ see above..} do begin
      fs.Read(aPacket, sizeof(TPacket));
      parse(aPacket); //defined somewhere else...
      //however, this should handle the 'endless loop' scenario..
      if (fs.size - fs.position < sizeof(TPacket) then break;
      fs.position := fs.position + sizeof(TPacket); //inc the position
    end;
  finally
    fs.free; //closes stream
  end;
end;

Something like that.. I once wrote a unit that reads/writes ZX Spectrum SNA 
files and lets you see the dump of the memory using a similar technique.

The above is untested, it might not work.. should give you the jist though.


--

"Computer games don't affect kids; I mean if Pac-Man affected us as kids, 
we'd all be running around in darkened rooms, munching magic pills and 
listening to repetitive electronic music." 
Kristian Wilson, 
Nintendo, Inc, 1989

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