Solved

Stupid Question (LoadLibrary)

Posted on 2010-09-17
9
762 Views
Last Modified: 2012-05-10
Hello,

This a very stupid quesiton (maybe)... but, i prefer to ask! hehe

Example

TSomethingW = record
  FuncW: function (Something: PWideChar): Boolean; StdCall;
  hLib: THandle;
end;
PSomethingW = ^TSomethingW;

TSomethingA = record
  FuncA: function (Something: PAnsiChar): Boolean; StdCall;
  hLib: THandle;
end;
PSomethingA = ^TSomethingA;

var
  SomethingW: PSomethingW;
  SomethingA: PSomethingA;
begin
  New(SomethingW);
  FillChar(SomethingW^, SizeOf(TSomethingW), 0);
  //looking for unicode function, if supported
  SomethingW^.hLib := LoadLibrary(somedll.dll);
  if LongBool(SomethingW^.hLib) then
  begin
    SomethingW^.FuncW := GetProcAddress(SomethingW^.hLib, 'SomethingW');

    //now we check if there is unicode support for this DLL, if not, its ANSI only
    if SomethingW^.FuncW = nil then
    begin
      //its ANSI and supposed to have a "SomethingA" exported func to work with ansi
      //but, i need to FreeLibrary for SomethingW^ and LoadLibrary for SomethingA or i can simple
      New(SomethingA);
      FillChar(SomethingA^, SizeOf(TSomethingA), 0);
      SomethingA^.hInstance := SomethingW^.hInstance; //?!?!?!?!?
      Dispose(SomethingW); //freeing
  end;

i need to freelibrary for somethingW and loadlibrary for somethingA or i can just pass the Handle of loaded library to SomethingA?

Regards,
Carlos
0
Comment
Question by:cebasso
  • 4
  • 3
  • 2
9 Comments
 
LVL 14

Expert Comment

by:systan
ID: 33703224
So thus the code has a problem for you?   I see your code is Ok.
but Im not sure  if you can pass the load from w to a with this code, and why are you doing this? for what reason?
SomethingA^.hInstance := SomethingW^.hInstance;
0
 
LVL 4

Author Comment

by:cebasso
ID: 33703278
Hello!
My program has a plugin framework... i have a struct/record for ANSI and WIDE(Unicode)

For old plugins, its ANSI and new plugins WIDE
For backward compatibility i need to support ANSI yet
So, with a new version of the engine, first i check if the plugin was upgraded to WIDE, if not, i use the old Struct (ANSI)
But, i load it from a StructW = WIDE, if there is no unicode support, then i load the old structA = ANSI... my doubt is, if i can just pass the loaded handle to the StructA^.hLib and use to call the plugin, or if i need to FreeLibrary at the StructW^.hLib and load for StructA^.hLib like my example above!
0
 
LVL 14

Expert Comment

by:systan
ID: 33703501
I guess you can't, Delphi doesn't support automatic type conversions betwwen Ansi and Wide string types.  Someone correct me if I'm wrong.
0
Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 4

Author Comment

by:cebasso
ID: 33703778
i think that you dont understood hehe
but no problem, i found a way!
i can't gave you the points, i'm sorry...
thank you anyway!
Cheers!
0
 
LVL 32

Accepted Solution

by:
ewangoya earned 500 total points
ID: 33703981
 No need to unload the library, just pass it on since it has both functions for unicode and ansi

  PSomethingW = ^TSomethingW;
  TSomethingW = record
    FuncW: function (Something: PWideChar): Boolean; StdCall;
    hLib: THandle;
  end;

  PSomethingA = ^TSomethingA;
  TSomethingA = record
    FuncA: function (Something: PAnsiChar): Boolean; StdCall;
    hLib: THandle;
  end;

function SupportsUnicode(AHandle: THandle; const AFunctionName: string): Boolean;
var
  FunctPointer: Pointer;
begin
  FuntionPointer := GetProcAddress(AHandle, AFunctionName);
  Result := FunctionPointer <> nil;
end;

procedure YourProcedure;
var
  LibraryHandle: THandle;
  SomethingW: PSomethingW;
  SomethingA: PSomethingA;
begin
  LibraryHandle := LoadLibrary('somedll.dll');
  if LibraryIsValid then
    try
      if SupportsUnicode(LibraryHandle, 'SomethingW') then
      begin
        New(SomethingW);
        FillChar(SomethingW^, SizeOf(TSomethingW), 0);
        SomethingW^.hLib := LibraryHandle;
        try
          SomethingW^.FuncW := GetProcAddress(SomethingW^.hLib, 'SomethingW');
          //do your work
        finally
          Dispose(SomethingW);
        end;
      end
      else
      begin
        New(SomethingA);
        FillChar(SomethingA^, SizeOf(TSomethingA), 0);
        SomethingA^.hLib := LibraryHandle;
        try
          SomethingA^.FuncA := GetProcAddress(SomethingW^.hLib, 'SomethingA');
          //do your work
        finally
          Dispose(SomethingA);
        end;
      end;
    finally
      FreeLibrary(LibraryHandle);
    end;
  end;
0
 
LVL 32

Expert Comment

by:ewangoya
ID: 33704008
Answer is you don't need to unload the library, look at my last comment.
0
 
LVL 32

Expert Comment

by:ewangoya
ID: 33704055
Sorry typo

function SupportsUnicode(AHandle: THandle; const AFunctionName: string): Boolean;
var
  FunctPointer: Pointer;
begin
  FunctPointer := GetProcAddress(AHandle, PChar(AFunctionName));
  Result := FunctPointer <> nil;
end;
0
 
LVL 4

Author Closing Comment

by:cebasso
ID: 33704166
Hey thanks!

But i still need a hLib var at the Struct since it will be added in a TList, so latelly i can know the instance of the plugin :D
But you answered my question, if its needed to unload in StructW first and re-load for StructA.

Cheers!
0
 
LVL 4

Author Comment

by:cebasso
ID: 33704181
@systan thank you too for starting to help me!

Best Regards!
0

Featured Post

Networking for the Cloud Era

Join Microsoft and Riverbed for a discussion and demonstration of enhancements to SteelConnect:
-One-click orchestration and cloud connectivity in Azure environments
-Tight integration of SD-WAN and WAN optimization capabilities
-Scalability and resiliency equal to a data center

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
Have you ever had your Delphi form/application just hanging while waiting for data to load? This is the article to read if you want to learn some things about adding threads for data loading in the background. First, I'll setup a general applica…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question