Forum > Windows
Issue With DLL
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BSaidus:
Hello;
I want to write a DLL and export some function from it, the countent of DLL functions encapsulate mORMot
functions and classes to help.
this is a source code.
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- library ucNetProxy;{$mode delphi}{$H+}uses Classes, Interfaces, { you can add units after this } ucfNetProxy ; exportsfQueryExportConnection, // export a global variable gfP: : TSQLDBConnectionProperties ; .fQueryInitConnectionsToServer, // export a Init connection to Server .fQueryGetSQLQR // get String from Server .; begin Dll_Process_Detach_Hook := @Dll_UC_ExitPoint; Dll_Thread_Attach_Hook := @Dll_UC_EntryPoint; Dll_Thread_Detach_Hook := @Dll_UC_ExitPoint;end.
And the declaration of functions is :
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---unit ucfNetProxy; {$mode delphi}{$H+} interface uses Classes, SysUtils, jsonConf, Forms, //SynDBMidasVCLExtra, mORMot, SynDBMidasVCL, SynDB, //TQuery SynTable, //SynDBVCL, mORMotMidasVCL, SynDBRemote, // Remote Access SynCommons //SynDBDataset, ; type TUCCntConfig = record host, port, // 127.0.0.1:7443 db, // medic user, pass: String; // user/pass end; // DLL relatedprocedure Dll_UC_EntryPoint(dllparam : PtrInt);procedure Dll_UC_ExitPoint(dllparam : PtrInt); function fQueryInitConnectionsToServer ():Boolean; stdcall;function fQueryGetSQLQR ( var oQuery: TQuery; iSQLRQ: Integer): Boolean; stdcall;function fQueryExportConnection (): Pointer; stdcall; { ------------------------------------------------------------------------------------------------------- } { Global vars } var gfP : TSQLDBConnectionProperties; gSQLCache : TStringList; gJConfig : TUCCntConfig; gId : Integer ; // Id for patients global gBUseCache: Boolean; implementation function fQueryGetConfig(): TUCCntConfig;var fJson: TJSONConfig; fApp: String;begin fApp := ChangeFileExt(Application.ExeName, '.json'); fJson := TJSONConfig.Create( nil ); fJson.Filename := fApp; try Result.host := fJson.GetValue('/httpcnt/host' ,'127.0.0.1'); Result.port := fJson.GetValue('/httpcnt/port' ,'7443' ); Result.db := fJson.GetValue('/httpcnt/dbase' ,'medic1' ); Result.user := fJson.GetValue('/httpcnt/user' ,'user' ); Result.pass := fJson.GetValue('/httpcnt/pass' ,'pass' ); finally fJson.Free; end;end; function fQueryHttpConnectionSQL ( ): TSQLDBConnectionProperties;var sHostPort: String;begin // Result is NULL Result := nil; // See if Global gfP is, and FreeIt if gfP <> nil then FreeAndNil(gfP); // construct host:port sHostPort := gJConfig.host + ':' + gJConfig.port; // construct Connection String Result := TSQLDBWinHTTPConnectionProperties.Create( sHostPort , gJConfig.db, gJConfig.user, gJConfig.pass); // Add widestring support Result.VariantStringAsWideString := true; // see if object is Created. if Result = nil then raise exception.Create( 'Error connecting to server... ' ); end; procedure Dll_UC_EntryPoint(dllparam: PtrInt);begin fQueryInitConnectionsToServer();end; procedure Dll_UC_ExitPoint(dllparam: PtrInt);begin if gfP <> nil then begin FreeAndNil(gfP); end;end; function fQueryInitConnectionsToServer(): Boolean; stdcall;begin Result := False; gJConfig := fQueryGetConfig(); gfP := fQueryHttpConnectionSQL(); Result := True;end; function fQueryGetSQLQR (var oQuery: TQuery; iSQLRQ: Integer): Boolean; stdcall;var fQuery: TQuery ; fSQL: string; fIndex: Integer; fNc: TSQLDBConnection;begin Result := False; //Screen.Cursor := crHourGlass; try //if oQuery = nil then // oQuery := TQuery.Create( gfP.NewConnection ); // //oQuery.SQL.Clear; //if ( gSQLCache.IndexOfObject(TObject(iSQLRQ)) <> -1 ) and ( gBUseCache ) then //begin // fIndex := gSQLCache.IndexOfObject(TObject(iSQLRQ)); // fSQL := gSQLCache.Strings[fIndex]; // oQuery.SQL.Text := fSQL; // oQuery.Tag := iSQLRQ; //end //else begin fNc := gfP.NewConnection; fQuery := TQuery.Create( fNc ); try try fQuery.SQL.Add( ' SELECT qr_sqltxt FROM uc_qrsql WHERE qr_id = ' + IntToStr(iSQLRQ) ) ; fQuery.Open; //if fQuery.RecordCount = 0 then //begin // Lnc := oQuery.Connection; // FreeAndNil( Lnc ); // FreeAndNil( oQuery ); // raise Exception.Create('No SQLQr N: in the scope !!'); //end; fSQL := fQuery.FieldByName('qr_sqltxt').AsString; oQuery.SQL.Text := fSQL; oQuery.Tag := iSQLRQ; //gSQLCache.AddObject( fSQL, TObject(iSQLRQ) ); // Add SQL text to Cach except raise; end; finally fQuery.Free; fNc.Free; end; end; finally //Screen.Cursor := crDefault; end; Result := True; // end; function fQueryExportConnection(): Pointer; stdcall;begin Result := @gfP;end; end.
What Expected:
Export the global variable:
--- Code: --- gfP : TSQLDBConnectionProperties;
--- End code ---
from the DLL. (I know that fpc do not allow exporting variables).
I used
--- Code: ---function fQueryExportConnection(): Pointer; stdcall;
--- End code ---
to export it as a Pointer ( sadly it do not work.)
this is a portion of test program:
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---// ...function fQueryInitConnectionsToServer():Boolean; stdcall; external 'ucNetProxy.dll';function fQueryGetSQLQR (var oQuery: TQuery; iSQLRQ: Integer): Boolean; stdcall; external 'ucNetProxy.dll';function fQueryExportConnection(): Pointer; stdcall; external 'ucNetProxy.dll'; var Form1: TForm1; gfP : TSQLDBConnectionProperties; pfP : Pointer; implementation {$R *.lfm} { TForm1 }// Button to initialise the system.procedure TForm1.btnInitClick(Sender: TObject);begin fQueryInitConnectionsToServer(); pfP := fQueryExportConnection(); gfP := TSQLDBConnectionProperties(pfP^);end; After clicking the Button
--- Code: ---procedure TForm1.btnInitClick(Sender: TObject);
--- End code ---
the program freeze.
So do you have any technic to solve this .
Thanks
PascalDragon:
--- Quote from: BSaidus on June 07, 2021, 01:25:16 pm ---I want to write a DLL and export some function from it, the countent of DLL functions encapsulate mORMot
functions and classes to help.
--- End quote ---
You need to write a clean, flat API. Do not pass class instances across the DLL boundary and expect them to be called correctly. This might work in most situations, but in will just as well blow up upon the smallest differences. Also you must not raise Exceptions across the DLL boundary, because you can't filter them using a on-clause.
Thus you must use opaque pointers (which can be the class instances to simplify the implementation) and essentially provide import functions for all methods you'd like to call on these (these functions then take that opaque pointer as "Self" parameter). Exceptions must be caught in those functions and you need to provide them as results or some GetLastError-like funktionality.
abouchez:
Sorry for responding so late.
The natural way of communicating with a mORMot DLL is to use its TRestServer.ExportServerGlobalLibraryRequest in mORMot 2 for instance or TSQLRestServer.ExportServer for mORMot 1.
In fact, you expose a REST server hosted by the DLL using an in-process JSON stream, and it will be used for efficient marshaling and memory allocation between the library and the mORMot kernel. It is easier to use than a full API, and it will work as a regular mORMot client on the consumer/executable side: then you could use interface based services in your main executable, and the mORMot ExportServer* wrapper will do all the marshalling and memory management for secure and efficient process.
One big advantage of this architecture, is that it would be easy to switch from a DLL hosted process to an external REST/HTTPS or WebSockets link in the future, if needed.
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