pluginmanager.pas

siMail, siMail, siMail, siMail

(*
# (C) Copyright 2004
# Miha Vrhovnik, [e-mail]
#
# The contents of this file are subject to the Mozilla Public License
# Version 1.1 (the "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
# http://www.mozilla.org/MPL/MPL-1.1.html
#
# Software distributed under the License is distributed on an "AS IS" basis,
# WITHOUT WARRANTY OF ANY KIND, either expressed or implied. See the License for
# the specific language governing rights and limitations under the License.
#
# The Initial Developer of the Original Code is Miha Vrhovnik (Slovenia).
# Portions created by Miha Vrhovnik are Copyright (c)2004.
# All Rights Reserved.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
#==============================================================================
# Contributor(s):
#==============================================================================
# Version History:
#==============================================================================
*)
unit pluginManager;

interface

uses
  SysUtils, Classes, Windows, Forms, BasePluginInterface;

type TPluginManager = class
  private
    FPluginFolder: String;
    FList: TList;
    function GetCount: Integer;
    function GetPlugin(Index: Integer): IsiMailBasePlugin;
  public
    constructor Create;
    destructor Destroy; override;
    function  AddCustomPlugin(plugin: IsiMailBasePlugin): Boolean;
    procedure LoadPlugins;
    procedure LoadPlugin(FileName: string);
    property Plugin[Index: Integer]: IsiMailBasePlugin read GetPlugin;
  published
    property Count: Integer read GetCount;
    property PluginFolder: String read FPluginFolder write FPluginFolder;
end;


type TPluginInfo = class(TObject)
  public
    Handle: HINST;
    PlugIn: IsiMailBasePlugin;
end;

type ELoadPluginError = class(Exception);

implementation

{ TPluginManager }

function TPluginManager.AddCustomPlugin(plugin: IsiMailBasePlugin): Boolean;
var PI: TPluginInfo;
begin
  PI := TPluginInfo.Create;
  PI.PlugIn := plugin;

  FList.Add(PI);
end;

constructor TPluginManager.Create;
begin
  inherited Create;
  FList := TList.Create;
end;

destructor TPluginManager.Destroy;
var i: Integer;
var PI: TPluginInfo;
begin
  for i := 0 to FList.Count - 1 do begin
    PI := FList.Items[i];
    PI.PlugIn := nil;
    FreeLibrary(PI.Handle);
    FreeAndNil(PI);
  end;
  FreeAndNil(FList);
  inherited Destroy;
end;

function TPluginManager.GetCount: Integer;
begin
  Result := FList.Count;
end;

function TPluginManager.GetPlugin(Index: Integer): IsiMailBasePlugin;
begin
  Result := TPluginInfo(FList.Items[Index]).PlugIn;
end;

procedure TPluginManager.LoadPlugin(FileName: string);
type
  TRegisterPlugin = function: IsiMailBasePlugin; stdcall;
var LibHandle: Integer;
var RegisterProc: TRegisterPlugin;
var PlugIn: IsiMailBasePlugin;
begin
  LibHandle := 0;

  LibHandle := LoadLibrary(PChar(FileName));

  if LibHandle = 0 then
    raise ELoadPluginError.CreateFmt('Couldn''t load plug-in: %s', [FileName]);
  try
   RegisterProc := GetProcAddress(LibHandle, 'RegisterPlugin');
   if not Assigned(RegisterProc) then
     raise ELoadPluginError.CreateFmt('Couldn''t find ''%s'' function in plug-in: %s', ['RegisterPlugin', FileName]);
    // initialize the plugin and add it to list
    PlugIn := RegisterProc;
    if AddCustomPlugin(PlugIn) then  begin
      TPluginInfo(FList.Last).Handle := LibHandle;
    end;
  except
    RegisterProc := nil;
    FreeLibrary(LibHandle);
  end;

end;

procedure TPluginManager.LoadPlugins;
var FileName: string;
var Found: Integer;
var Path: string;
var Sr: TSearchRec;
begin
  // if the PluginPath is blank, we load from the app's folder.
  if FPluginFolder = '' then
    Path := ExtractFilePath(Application.ExeName)
  else
    Path := FPluginFolder;

  Path := IncludeTrailingPathDelimiter(Path);

  try
    try
      Found := FindFirst(Path + '*.dll', faAnyFile, Sr);
      while Found = 0 do
      begin
        FileName := Sr.Name;
        //! If one plugin made problems -> no other plugins where loaded
        //! To avoid that the try-except block was wrapped around here...
        try
          LoadPlugin(Path + FileName);
        except
        end;
        Found := FindNext(Sr);
      end;
    except
      on E: Exception do
          raise;
    end;
  finally
    SysUtils.FindClose(Sr);
  end;
end;

end.