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{ Old file: tbs0098.pp }
{ File type casts are not allowed (works in TP7) OK 0.99.1 (FK) }
program Test;
{ Show how to seek to an OFFSET (not a line number) in a textfile, }
{ without using asm. Arne de Bruijn, 1994, PD }
uses Dos; { For TextRec and FileRec }
var
F:text;
L:longint;
S:string;
begin
{ Create temp }
assign(F,'tb0084.tmp'); { Assign F to itself }
rewrite(f);
for l:=1 to 100 do
writeln('Hello world');
close(f);
assign(F,'tb0084.tmp'); { Assign F to itself }
reset(F); { Open it (as a textfile) }
ReadLn(F); { Just read some lines }
ReadLn(F);
ReadLn(F);
FileRec((@F)^).Mode:=fmInOut; { Set to binary mode }
{ (The (@F)^ part is to let TP 'forget' the type of the structure, so }
{ you can type-caste it to everything (note that with and without (@X)^ }
{ can give a different value, longint(bytevar) gives the same value as }
{ bytevar, while longint((@bytevar)^) gives the same as }
{ longint absolute Bytevar (i.e. all 4 bytes in a longint are readed }
{ from memory instead of 3 filled with zeros))) }
FileRec((@F)^).RecSize:=1; { Set record size to 1 (a byte)}
L:=(FilePos(File((@F)^))-TextRec(F).BufEnd)+TextRec(F).BufPos;
{... This line didn't work the last time I tried, it chokes on the "File"
typecasting thing.}
{ Get the fileposition, subtract the already readed buffer, and add the }
{ position in that buffer }
TextRec(F).Mode:=fmInput; { Set back to text mode }
TextRec(F).BufSize:=SizeOf(TextBuf); { BufSize overwritten by RecSize }
{ Doesn't work with SetTextBuf! }
ReadLn(F,S); { Read the next line }
WriteLn('Next line:',S); { Display it }
FileRec((@F)^).Mode:=fmInOut; { Set to binary mode }
FileRec((@F)^).RecSize:=1; { Set record size to 1 (a byte)}
Seek(File((@F)^),L); { Do the seek }
{... And again here.}
TextRec(F).Mode:=fmInput; { Set back to text mode }
TextRec(F).BufSize:=SizeOf(TextBuf); { Doesn't work with SetTextBuf! }
TextRec(F).BufPos:=0; TextRec(F).BufEnd:=0; { Reset buffer counters }
ReadLn(F,S); { Show that it worked, the same }
WriteLn('That line again:',S); { line readed again! }
Close(F); { Close it }
Erase(F);
end.
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