unit uMyDLL;

interface

uses
  Windows;


type
    PMyVar = ^TMyVar;
    TMyVar = record
        iStrLen: Longint;
        sValue: PAnsiChar;
        iValue: Longint;
        dValue: double;
    end;

    PMyField = ^TMyField;
    TMyField = record
        iStrLen: Longint;
        sName: PAnsiChar;
        iDatatype: Longint;
        iMaxlen: Longint;
        iFlags: Longint;
    end;


    procedure mydll_free;
    function mydll_load( name: PChar ): boolean;

var
    mydll_handle: HMODULE = 0;

    mydll_createNewConnection: function: Longint; stdcall;
    mydll_setOptions: procedure( iConn: Longint; sHost: PAnsiChar; iPort: Longint; sUser: PAnsiChar; sPass: PAnsiChar ); stdcall;

    mydll_connect: function( iConn: Longint ): bool; stdcall;
    mydll_disconnect: procedure( iConn: Longint ); stdcall;
    mydll_closeConnection: procedure( iConn: Longint ); stdcall;

    mydll_selectDatabase: function( iConn: Longint; sDBName: PAnsiChar ): bool; stdcall;
    mydll_openQuery: function( iConn: Longint; sQuery: PAnsiChar ): bool; stdcall;
    mydll_close: procedure( iConn: Longint ); stdcall;
    mydll_isLast: function( iConn: Longint ): bool; stdcall;
    mydll_next: function( iConn: Longint ): bool; stdcall;

    mydll_getFieldCount: function( iConn: Longint ): Longint; stdcall;
    mydll_getRecordCount: function( iConn: Longint ): Longint; stdcall;
    mydll_fetchValue: function( iConn: Longint; iIndex: Longint; iDatatype: Longint; pVar: PMyVar ): bool; stdcall;
    mydll_fetchField: function( iConn: Longint; iIndex: Longint; pField: PMyField ): bool; stdcall;


implementation

uses
  SysUtils;

procedure assign_proc(var proc: FARPROC; name: PAnsiChar);
begin
  proc := GetProcAddress( mydll_handle, name );
  if proc = nil then
  begin
    raise Exception.Create('dll function ' + name + ' doesn''t exist');
  end;
end;

function mydll_load(name: PChar): boolean;
begin
  mydll_free;
  if name = nil then
  begin
    name := 'mydll.dll';
  end;
  mydll_handle := LoadLibrary(name);
  if mydll_handle = 0 then
  begin
    Result := false;
  end
  else
  begin
    assign_proc(@mydll_createNewConnection, 'mydll_createNewConnection');
    assign_proc(@mydll_setOptions, 'mydll_setOptions');
    assign_proc(@mydll_connect, 'mydll_connect');
    assign_proc(@mydll_disconnect, 'mydll_disconnect');
    assign_proc(@mydll_closeConnection, 'mydll_closeConnection');
    assign_proc(@mydll_selectDatabase, 'mydll_selectDatabase');
    assign_proc(@mydll_openQuery, 'mydll_openQuery');
    assign_proc(@mydll_close, 'mydll_close');
    assign_proc(@mydll_isLast, 'mydll_isLast');
    assign_proc(@mydll_next, 'mydll_next');

    assign_proc(@mydll_getFieldCount, 'mydll_getFieldCount');
    assign_proc(@mydll_getRecordCount, 'mydll_getRecordCount');
    assign_proc(@mydll_fetchValue, 'mydll_fetchValue');
    assign_proc(@mydll_fetchField, 'mydll_fetchField');

    Result := true;
  end;
end;

procedure mydll_free;
begin
  if mydll_handle <> 0 then
  begin
    FreeLibrary( mydll_handle );
  end;

  mydll_handle := 0;
end;

INITIALIZATION
begin
  mydll_load(nil);
end;

FINALIZATION
begin
  mydll_free;
end;

end.