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{ Copyright (C) 2009 Bas Steendijk and Peter Green
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For conditions of distribution and use, see copyright notice in zlib_license.txt
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which is included in the package
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----------------------------------------------------------------------------- }
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unit readtxt2;
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interface
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{
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readtxt, version 2
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by beware
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this can be used to read a text file exposed as a tstream line by line.
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automatic handling of CR, LF, and CRLF line endings, and readout of detected line ending type.
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fast: 1.5-2 times faster than textfile readln in tests.
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}
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uses
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classes,sysutils;
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const
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bufsize=4096;
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eoltype_none=0;
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eoltype_any=0;
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eoltype_cr=1;
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eoltype_lf=2;
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eoltype_crlf=3;
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type
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treadtxt=class(tobject)
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private
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buf:array[0..bufsize-1] of byte;
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numread:integer;
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bufpointer:integer;
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currenteol,preveol:integer;
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fileeof,reachedeof:boolean;
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fdetectedeol:integer;
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procedure checkandread;
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public
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sourcestream:tstream;
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destroysourcestream:boolean;
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allowedeol:integer;
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constructor create(asourcestream: tstream; adestroysourcestream:boolean);
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constructor createf(filename : string);
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function readline:ansistring;
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function eof:boolean;
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destructor destroy; override;
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property detectedeol : integer read fdetectedeol;
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end;
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implementation
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constructor treadtxt.create(asourcestream: tstream; adestroysourcestream:boolean);
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begin
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inherited create;
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sourcestream := asourcestream;
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destroysourcestream := adestroysourcestream;
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//if sourcestream.Position >= sourcestream.size then fileeof := true;
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bufpointer := bufsize;
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end;
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constructor treadtxt.createf(filename: string);
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begin
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create(tfilestream.create(filename,fmOpenRead or fmShareDenyWrite),true);
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end;
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procedure treadtxt.checkandread;
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begin
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if bufpointer >= numread then begin
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numread := sourcestream.read(buf,bufsize);
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bufpointer := 0;
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if numread = 0 then fileeof := true;
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end;
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end;
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function treadtxt.readline;
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var
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a,b,c,d:integer;
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prevchar : integer;
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trimchar : boolean;
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begin
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prevchar := 0;
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result := '';
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repeat
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checkandread;
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b := numread-1;
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trimchar := false;
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{core search loop begin}
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d := -1;
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for a := bufpointer to b do begin
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c := buf[a];
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//check if the character can possibly be a line ending before getting
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//into the more complex checks that depend on eol type
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if (c = 10) or (c = 13) then case allowedeol of
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eoltype_any: begin
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d := a;
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break;
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end;
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eoltype_cr: begin
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if (c = 13) then begin
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d := a;
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break;
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end;
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end;
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eoltype_lf: begin
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if (c = 10) then begin
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d := a;
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break;
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end;
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end;
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eoltype_crlf: begin
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if (c = 10) and (prevchar= 13) then begin
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d := a;
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trimchar := true;
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break;
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end;
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prevchar := c;
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end;
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else begin
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raise exception.create('undefined eol type set');
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end;
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end;
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prevchar := c;
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end;
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{core search loop end}
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c := length(result);
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if (d = -1) then begin
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{ran out of buffer before end of line}
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b := numread-bufpointer;
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setlength(result,c+b);
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move(buf[bufpointer],result[c+1],b);
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bufpointer := numread;
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if fileeof then begin
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{we reached the end of the file, return what we have}
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reachedeof := true;
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exit;
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end;
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end else begin
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preveol := currenteol;
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currenteol := buf[d];
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{end of line before end of buffer}
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if (currenteol = 10) and (preveol = 13) and (bufpointer = d) then begin
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{it's the second EOL char of a DOS line ending, don't cause a line}
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bufpointer := d+1;
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fdetectedeol := eoltype_crlf;
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end else begin
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if fdetectedeol = eoltype_none then begin
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if (currenteol = 10) then fdetectedeol := eoltype_lf else fdetectedeol := eoltype_cr;
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end;
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b := d-bufpointer;
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if trimchar then begin
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setlength(result,c+b-1);
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move(buf[bufpointer],result[c+1],b-1);
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bufpointer := d+1;
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end else begin
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setlength(result,c+b);
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move(buf[bufpointer],result[c+1],b);
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bufpointer := d+1;
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end;
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{EOF check}
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if fileeof then begin
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if (bufpointer >= numread) then reachedeof := true;
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if (currenteol = 13) and (bufpointer = numread-1) then if (buf[bufpointer] = 10) then reachedeof := true;
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end;
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exit;
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end;
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end;
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until false;
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end;
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function treadtxt.eof:boolean;
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begin
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checkandread;
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result := ((bufpointer >= numread) and fileeof) or reachedeof;
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end;
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destructor treadtxt.destroy;
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begin
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if destroysourcestream then if assigned(sourcestream) then sourcestream.destroy;
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inherited destroy;
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end;
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end.
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