Использование функции из DLL

Delphi , Файловая система , DLL и PlugIns

Автор: Xavier Pacheco

{
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.

Статья Использование функции из DLL раздела Файловая система DLL и PlugIns может быть полезна для разработчиков на Delphi и FreePascal.

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