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howl...@mail.airmail.net (TorchIT)

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Reading a file with ctrl Z before end of file

Hello all,
Is there anyway to read a file that has a control z  before the end of
file. I have a file created by a redirection of a dos command.  In that
file is the end of file mark but it comes before the actual eof.  I have
tried to declare the file as file of char thinking I could keep on
reading, but it only reads till the control z which I know is the eof
marker. I think the way to do it is a for loop but I can't figure out
the loop structure.  Can any one help or did I make my problem clear as
mud?
Thanks,
HowarD

 
Asbj?r

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


Quote
TorchIT wrote:

> Hello all,
> Is there anyway to read a file that has a control z  before the end of
> file. I have a file created by a redirection of a dos command.  In that
> file is the end of file mark but it comes before the actual eof.  I have
> tried to declare the file as file of char thinking I could keep on
> reading, but it only reads till the control z which I know is the eof
> marker. I think the way to do it is a for loop but I can't figure out
> the loop structure.  Can any one help or did I make my problem clear as
> mud?
> Thanks,
> HowarD

Hmm... I'm not sure, but instead of using the EOF function, can't you keep reading, and keep track of the
bytes, until you reached the end, using the lenght_of_file function (i know it's not the proper name, but.. :)
I'm not sure how the lenght_of_file function works, so... And perhaps the read procedure doesn't like reading
^Z. I don't know, give it a try.

- Asbj?rn

Bob Scho

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


Quote
> Is there anyway to read a file that has a control z  before the end of
> file. I have a file created by a redirection of a dos command.  In that
> file is the end of file mark but it comes before the actual eof.  I have
> tried to declare the file as file of char thinking I could keep on
> reading, but it only reads till the control z which I know is the eof
> marker. I think the way to do it is a for loop but I can't figure out
> the loop structure.  Can any one help or did I make my problem clear as
> mud?

Howard,
     This is, in my opinion, an Implementation Bug (Feature?) of
Borland's Pascal dialect.  The file type "text" should treat ^Z as EOF
if that's what your operating system suggests, as this file type is
meant to be implementation-specific, and tailored to the concept of
lines and (logical) EOF.
     The file type "char" should, on the other hand, treat the entire
character set, which is also somewhat implementation-specific, but is
probably either 7-bit Ascii, 8-bit Ascii, or EBCDIC; since we're talking
PC-DOS, it's probably 8-bit Ascii, and ^Z is just another Ascii
character.
     However, it looks like Borland is giving this character special
significance, and using it as EOF.  [Incidently, you might wonder if it
treats ^@, 00H, the null character, as a real character, or whether it
simply skips over it].  If so, you cannot use FILE OF char to solve your
problem.
     How about trying PACKED FILE OF bytetype, where bytetype is defined
as the restricted integer range -128 .. 127?  You may have to experiment
a bit, as it is again somewhat implementation-dependent whether this
will work (an alternative declaration that might work if this doesn't
is 0 .. 255).  Now ^Z is simply the number 26.  You can easily convert
these bytes back into characters using the chr() function (though you
may need to be careful if you get 8-bit Ascii values and have defined
bytetype as -128..127).

Bob Schor
Pascal Enthusiast

A Dude Who Progra

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


Quote
Bob Schor <bsc...@vms.cis.pitt.edu> wrote:
>     However, it looks like Borland is giving this character special
>significance, and using it as EOF.  

Would probably agree with you...

Glenn Grotzinger
Web Page: http://www.geocities.com/Paris/3537
Writer of Excellent Training Manual known as the TP Tutorial.
You may find this material on the web page eventually.
Other interesting things will eventually exist as well.

Scott Earnes

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


Quote
TorchIT wrote:
> Hello all,
> Is there anyway to read a file that has a control z  before the end of
> file. I have a file created by a redirection of a dos command.  In that
> file is the end of file mark but it comes before the actual eof.  I have
> tried to declare the file as file of char thinking I could keep on
> reading, but it only reads till the control z which I know is the eof
> marker. I think the way to do it is a for loop but I can't figure out
> the loop structure.  Can any one help or did I make my problem clear as
> mud?

No, not that hard to understand.  Rather than worry about it in code, I
usually just use this little program as a sort of filter to strip
problematic text files.

program stripEOFs;

{
 uneof.pas -- written by Scott Earnest (set...@ix.netcom.com)

 Quickly removes all offending EOF (ASCII #26) characters from a
 text file by changing them to ASCII #0.  This method will fail on
 read-only files, and is more  of a kludge than a good solution.

 Standard disclaimers apply.

Quote
}

type
  tblock = array[0 .. 32767] of byte;

var
  dblock : tblock;
  x : word;
  f : file;
  count : word;
  fp : longint;

begin
  if paramcount <> 1 then
    begin
      writeln ('Specify a file to strip EOF''s from!');
      halt;
    end;
  assign (f, paramstr(1));
  reset (f,1);
  fp := 0;
  while not eof(f) do
    begin
      fp := filepos(f);
      blockread (f, dblock, sizeof (tblock), count);
      for x := 0 to pred(count) do
        if dblock[x] = $1a then dblock[x] := $00;
      seek (f,fp);
      blockwrite (f, dblock, count);
    end;
  close (f);
end.

Quote
> Thanks,
> HowarD

--
Scott Earnest                      | _,-""-_,-""-_,-""-_,-""-_,-""-_,-"
|
set...@ix.netcom.com (primary)     | We now return you to our regularly
|
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|
ASS-War

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


You can convert your handle to a binary file handle, see the source of the
printer unit on the bonus disk.
Second, look for the filesize first and then read as many bytes as the
filesize is.

--
Greetings,
ASS-Ware.

           ,,,
          (o o)
 -----oOO--(_)--OOo-----
|       ASS-Ware        |
|    is watching you    |
 -----------------------

TorchIT <howl...@mail.airmail.net> wrote in article
<59ms2u$...@library.airnews.net>...

Quote
> Hello all,
> Is there anyway to read a file that has a control z  before the end of
> file. I have a file created by a redirection of a dos command.  In that
> file is the end of file mark but it comes before the actual eof.  I have
> tried to declare the file as file of char thinking I could keep on
> reading, but it only reads till the control z which I know is the eof
> marker. I think the way to do it is a for loop but I can't figure out
> the loop structure.  Can any one help or did I make my problem clear as
> mud?
> Thanks,
> HowarD

Frank Heckenba

Delphi Developer
Wed, 18 Jun 1902 08:00:00 GMT

Re:Reading a file with ctrl Z before end of file


Quote
Bob Schor <bsc...@vms.cis.pitt.edu> writes:
> > Is there anyway to read a file that has a control z  before the end of
> > file. I have a file created by a redirection of a dos command.  In that
> > file is the end of file mark but it comes before the actual eof.  I have
> > tried to declare the file as file of char thinking I could keep on
> > reading, but it only reads till the control z which I know is the eof
> > marker.
>      This is, in my opinion, an Implementation Bug (Feature?) of
> Borland's Pascal dialect. [...]
>      The file type "char" should, on the other hand, treat the entire
> character set [...]
>      However, it looks like Borland is giving this character special
> significance, and using it as EOF.

Not as far as I can see. Maybe it was different with earlier versions, but I
just tested with BP 7.0, and the file of char read properly behind the #26.

For text files: They do stop at the #26, that's how they're designed. If you
wnat to change this behaviour, take a look at:
http://www.mi.uni-erlangen.de/~heckenb/programs.htm#CrLf
This contains a program to convert unix style line breaks to Dos style. It can
be adapted to remove EOFs (the code will get even easier).

Hope this helps,
Frank

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