Multiple Concurrent DLLs

Example of WHAT?, can not see what you want? I guess you can do a DLL, since you say you have one that works? ? So I guess you want some, I do not know? Store Data in DLL I GUESS? ? ?

OK some code, but this is a just one way of Thousands to store Data, Here is a Library Code that has 3 export functions -

function AddToStorage(pName: PChar; Int1, Int2: Integer): Integer;
  // this will add a storage Item and set three datas to Item

function GetStorage(Index: Integer; out pName: PChar;
                    out Int1, Int2: Integer): Bool; export;
  // this will Get three datas from storage Item Index

function DeleteStorage(Index: Integer): Bool;
  // this will Delete a Storage Item

I use a TList in the DLL for the Storage, a TList has several methods for Item addition and changes, you should look at the Delphi Help for "TList" if you need any more methods in your DLL.

code for library - - -


library demoDLL;

uses
  SysUtils, Classes,
  Windows, Messages;


type
  PInfo = ^TInfo;
  TInfo = record
    Name: String;
    Int1, Int2: Integer;
    end;


var
Storage: TList;


// do NOT use Strings in a export DLL function
function AddToStorage(pName: PChar; Int1, Int2: Integer): Integer; export;
var
pInfo1: PInfo;
begin
// adds a new Item to Storage and returns it's index, or -1 for ERROR
Result := -1;
New(pInfo1);
pInfo1.Name := pName;
pInfo1.Int1 := Int1;
pInfo1.Int2 := Int2;
try  // not to have exception in DLL is beter, just return an ERROR result for function
  Storage.Add(pInfo1);
  except
  Exit;
  end;
Result := Storage.Count-1;
end;


function GetStorage(Index: Integer; out pName: PChar;
                    out Int1, Int2: Integer): Bool; export;
var
pInfo1: PInfo;
begin
// retrives Info data from Storage Item Index
Result := False;
pName := nil;
if (Index < 0) or (Index > Storage.Count-1) then Exit;

try
pInfo1 := Storage.Items[Index];
  except
  Exit;
  end;
pName := PChar(pInfo1.Name);
Int1 := pInfo1.Int1;
Int2 := pInfo1.Int2;
Result := True;
end;

function DeleteStorage(Index: Integer): Bool; export;
begin
// deletes an Index Item from storage
Result := False;
if (Index < 0) or (Index > Storage.Count-1) then Exit;
try
  Dispose(Storage.Items[Index]);
  Storage.Delete(Index);
  except
  Exit;
  end;
Result := True;
end;


procedure AttatchProc(cReason: Cardinal);
var
i: Integer;
begin
if (cReason = Dll_Process_Detach) then
 begin
 for i := 0 to Storage.Count -1 do
   Dispose(Storage.Items[i]);
 FreeAndNil(Storage);
 end;
end;

exports
  AddToStorage,
  GetStorage,
  DeleteStorage;


begin
DLLProc := @AttatchProc;
Storage := TList.Create;
end.


 = = = = = = = = =  = = =  = = = = = = = = =  = = = =

code for button Click in program to use DLL - - - -



procedure TForm1.sbut_DoStorageDLLClick(Sender: TObject);
var
hLibS: THandle;
AddToStorage: function(pName: PChar; Int1, Int2: Integer): Integer;
GetStorage: function(Index: Integer; out pName: PChar;
                    out Int1, Int2: Integer): Bool;
DeleteStorage: function(Index: Integer): Bool;

Int1, Int2, Index: Integer;
Name: String;
pName: PChar;

begin
// button Click
hLibS := LoadLibrary('demoDLL.dll');
if hLibS = 0 then
  begin
  ShowMessage('Did not load the DLL');
  Exit;
  end;

@AddToStorage := GetProcAddress(hLibS, 'AddToStorage');
if @AddToStorage = nil then
  begin
  ShowMessage('AddToStorage is nil');
  FreeLibrary(hLibS);
  Exit;
  end;

Name := 'John Programmer';
Int1 := 111;
Int2 := 222;

{when you create a NEW Document, you can store Info for that Document
with AddToStorage}
Index := AddToStorage(PChar(Name), Int1, Int2);
if Index > -1 then
  ShowMessage('AddToStorage Worked, Index is '+IntToStr(Index))
  else
  ShowMessage('ERROR - AddToStorage   FAILED');

Name := 'SomeOne Else Jr';
Int1 := 333;
Int2 := 444;

Index := AddToStorage(PChar(Name), Int1, Int2);
if Index > -1 then
  ShowMessage('AddToStorage Worked, Index is '+IntToStr(Index))
  else
  ShowMessage('ERROR - AddToStorage   FAILED');

{getStorage will get Data from Index Item}
@GetStorage := GetProcAddress(hLibS, 'GetStorage');
if @GetStorage = nil then
  begin
  ShowMessage('GetStorage is nil');
  FreeLibrary(hLibS);
  Exit;
  end;

if GetStorage(0, pName, Int1, Int2) then
  begin
  Name := pName;
  ShowMessage('GetStorage Worked,'#10'Int1 = '+IntToStr(Int1)+' Int2 = '+
               IntToStr(Int2)+' '+Name);
  end else
  ShowMessage('ERROR - GetStorage   FAILED');

FreeLibrary(hLibS);
end;

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but I was just guessing,