How Can I Efficiently Read The FIrst Few Lines of Many Files in Delphi

Question

I have a \"Find Files\" function in my program that will find text files with the .ged suffix that my program reads. I display the found results in an explorer-like window t

Answer 1

Sometimes oldschool pascal stylee is not that bad. Even though non-oo file access doesn't seem to be very popular anymore, ReadLn(F,xxx) still works pretty ok in situations like yours.

The code below loads information (filename, source and version) into a TDictionary so that you can look it up easily, or you can use a listview in virtual mode, and look stuff up in this list when the ondata even fires.

Warning: code below does not work with unicode.

program Project101;
{$APPTYPE CONSOLE}

uses
  IoUtils, Generics.Collections, SysUtils;

type
  TFileInfo=record
    FileName,
    Source,
    Version:String;
  end;

function LoadFileInfo(var aFileInfo:TFileInfo):Boolean;
var
  F:TextFile;
begin
  Result := False;
  AssignFile(F,aFileInfo.FileName);
  {$I-}
  Reset(F);
  {$I+}
  if IOResult = 0 then
  begin
    ReadLn(F,aFileInfo.Source);
    ReadLn(F,aFileInfo.Version);
    CloseFile(F);
    Exit(True)
  end
  else
    WriteLn('Could not open ', aFileInfo.FileName);
end;

var
  FileInfo:TFileInfo;
  Files:TDictionary;
  S:String;
begin
  Files := TDictionary.Create;
  try
    for S in TDirectory.GetFiles('h:\WINDOWS\system32','*.xml') do
    begin
      WriteLn(S);
      FileInfo.FileName := S;
      if LoadFileInfo(FileInfo) then
        Files.Add(S,FileInfo);
    end;

    // showing file information...
    for FileInfo in Files.Values do
      WriteLn(FileInfo.Source, ' ',FileInfo.Version);
  finally
    Files.Free
  end;
  WriteLn;
  WriteLn('Done. Press any key to quit . . .');
  ReadLn;
end.