{
Copyright © 1999 by Delphi 5 Developer's Guide - Xavier Pacheco and Steve Teixeira
}

library StrSrchLib;

uses
 Wintypes,
 WinProcs,
 SysUtils,
 Dialogs;

type
 { declare the callback function type }
 TFoundStrProc = procedure(StrPos: PChar); StdCall;

function SearchStr(ASrcStr, ASearchStr: PChar; AProc: TFarProc): Integer;
 stdcall;
{ This function looks for ASearchStr in ASrcStr. When if finds ASearchStr,
 the callback procedure referred to by AProc is called if one has been
 passed in. The user may pass nil as this parameter. }
var
 FindStr: PChar;
begin
 FindStr := ASrcStr;
 FindStr := StrPos(FindStr, ASearchStr);
 while FindStr <> nil do
 begin
 if AProc <> nil then
 TFoundStrProc(AProc)(FindStr);
 FindStr := FindStr + 1;
 FindStr := StrPos(FindStr, ASearchStr);
 end;
end;

exports
 SearchStr;
begin

end.

{
Copyright © 1999 by Delphi 5 Developer's Guide - Xavier Pacheco and Steve Teixeira
}

unit MainFrm;

interface

uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls,
 Forms, Dialogs, StdCtrls;

type
 TMainForm = class(TForm)
 btnCallDLLFunc: TButton;
 edtSearchStr: TEdit;
 lblSrchWrd: TLabel;
 memStr: TMemo;
 procedure btnCallDLLFuncClick(Sender: TObject);
 end;

var
 MainForm: TMainForm;
 Count: Integer;

implementation

{$R *.DFM}

{ Define the DLL's exported procedure }

function SearchStr(ASrcStr, ASearchStr: PChar; AProc: TFarProc): Integer; stdcall
 external
'STRSRCHLIB.DLL';

{ Define the callback procedure, make sure to use the StdCall directive }

procedure StrPosProc(AStrPsn: PChar); stdcall;
begin
 inc(Count); // Increment the Count variable.
end;

procedure TMainForm.btnCallDLLFuncClick(Sender: TObject);
var
 S: string;
 S2: string;
begin
 Count := 0; // Initialize Count to zero.
 { Retrieve the length of the text on which to search. }
 SetLength(S, memStr.GetTextLen);
 { Now copy the text to the variable S }
 memStr.GetTextBuf(PChar(S), memStr.GetTextLen);
 { Copy Edit1's Text to a string variable so that it can be passed to
 the DLL function }
 S2 := edtSearchStr.Text;
 { Call the DLL function }
 SearchStr(PChar(S), PChar(S2), @StrPosProc);
 { Show how many times the word occurs in the string. This has been
 stored in the Count variable which is used by the callback function }
 ShowMessage(Format('%s %s %d %s', [edtSearchStr.Text, 'occurs', Count,
 'times.']));
end;

end.