Nelp needed using PChar

[topcat01]

Hi,

I have searched the forum and google and wondered if anyone can answer the following:

This is my code for reading a pchar null terminated string from a file which seems to work ok, in this example I know the string is 16 bytes long.

  var
    CurrentFile : TFilestream;
    MyName : PChar;
              
    CurrentFile.ReadBuffer(MyName,16);
    Add('      Name: '+PChar(@MyName));

My question is if I don't know how long the string is can I use pchar to read a string from a file until it reads the null, if yes how?

I tried "CurrentFile.ReadBuffer(MyName,255);" (as 255 is max size of name) but the program crashes prob because the total filesize was only 50 bytes in size.

Hope I have made myself clear ?

 

[Glenn9999]

PChar is a pointer to a character. It's useful for reading null-terminated strings. The thing is though, you have to allocate space for it first, and work with that space. You can either do it from a Pascal string like I do in the code below (that's how I usually handle Windows API calls that want PChar types for input/output), or from an array of characters.

The output of this code to the file will be

TEST STRING#0

To find the length of a null-terminated string, you have to load it into the buffer and then search for #0.

var
  outfile: file;
  outPString: PChar;
  outstring: string;
begin
  AssignFile(outfile, 'TEST.FIL');
  rewrite(outfile, 1);
  outstring := 'TEST STRING' + #0;
  outPString := PChar(@outstring[1]);
  blockwrite(outfile, outPString^, length(Outstring));
  Closefile(outfile);
end;

Not sure that explains much, but hope it helps.

----------
Measurement is not management.

 

[topcat01]

Thanks for the reply glenn.

I've been looking at this for too long.

I read into an array and searched for null and all works now.

 

[roo0047]

Keep in mind that a TString IS an array.
array [1..length] of char; (byte[0] contains the length, up to 255)
Does NOT apply to THugeString.



Roo
Delphi Rules!