Как вызывать функцию 16-битной DLL из 32-битного приложения?

Вариант 1:

Author: Андрей Гусев (Andrey Gusev)

Source: Akzhan's Delphi-related VCL&WinAPI Tips'n'Tricks

Надо использовать Thunks.

Кусок работающего только под Windows 95 кода:

const
  Gfsr_SystemResources = 0;
  Gfsr_GdiResources = 1;
  Gfsr_UserResources = 2;
var
  hInst16: THandle;
  GFSR: Pointer;
{ Undocumented Kernel32 calls. }
function LoadLibrary16(LibraryName: PChar): THandle;
         stdcall; external kernel32 index 35;
procedure FreeLibrary16(HInstance: THandle);
          stdcall; external kernel32 index 36;
function GetProcAddress16(Hinstance: THandle; ProcName: PChar): Pointer;
         stdcall; external kernel32 index 37;
procedure QT_Thunk; cdecl; external kernel32 name 'QT_Thunk';
{ QT_Thunk needs a stack frame. }
{$StackFrames On}
{ Thunking call to 16-bit USER.EXE. The ThunkTrash argument
allocates space on the stack for QT_Thunk. }
function NewGetFreeSystemResources(SysResource: Word): Word;
var
  ThunkTrash: array[0..$20] of Word;
begin
  { Prevent the optimizer from getting rid of ThunkTrash. }
  ThunkTrash[0] := hInst16;
  hInst16 := LoadLibrary16('user.exe');
  if hInst16 < 32 then
    raise Exception.Create('Cannot load USER.EXE!');
  { Decrement the usage count. This doesn't really free the
    library, since USER.EXE is always loaded. }
  FreeLibrary16(hInst16);
  { Get the function pointer for the 16-bit function in USER.EXE. }
  GFSR := GetProcAddress16(hInst16, 'GetFreeSystemResources');
  if GFSR = nil then
    raise Exception.Create('Cannot get address of GetFreeSystemResources!');
  { Thunk down to USER.EXE. }
  asm
    push SysResource { push arguments }
    mov edx, GFSR { load 16-bit procedure pointer }
    call QT_Thunk { call thunk }
    mov Result, ax { save the result }
  end;
end;

Автор: Quality freeware from Sight&Sound, Slovenia, http://www.sight-sound.si

Вариант 2:

Source: https://delphiworld.narod.ru

Посылаю код для определения системных ресурсов (как в "Индикаторе ресурсов"). Использовалась статья "Calling 16-bit code from 32-bit in Windows 95".

{ GetFeeSystemResources routine for 32-bit Delphi.

Works only under Windows 9x }

unit SysRes32;

interface

const
  //Constants whitch specifies the type of resource to be checked

  GFSR_SYSTEMRESOURCES = $0000;
  GFSR_GDIRESOURCES    = $0001;
  GFSR_USERRESOURCES   = $0002;

// 32-bit function exported from this unit

function GetFeeSystemResources(SysResource: Word):Word;

implementation

uses
  SysUtils, Windows;

type

  //Procedural variable for testing for a nil
  TGetFSR = function(ResType: Word): Word; stdcall;

  //Declare our class exeptions

  EThunkError = class(Exception);
  EFOpenError = class(Exception);

var
  User16Handle : THandle = 0;
  GetFSR       : TGetFSR = nil;

//Prototypes for some undocumented API

function LoadLibrary16(LibFileName: PAnsiChar): THandle;
         stdcall; external kernel32 index 35;

function FreeLibrary16(LibModule: THandle): THandle;
         stdcall; external kernel32 index 36;

function GetProcAddress16(Module: THandle; ProcName: LPCSTR): TFarProc;
         stdcall; external kernel32 index 37;

procedure QT_Thunk; cdecl;
          external 'kernel32.dll' name 'QT_Thunk';

{$StackFrames On}

function GetFeeSystemResources(SysResource: Word):Word;
var
  EatStackSpace: String[$3C];
begin
  // Ensure buffer isn't optimised away
  EatStackSpace := '';
  @GetFSR:=GetProcAddress16(User16Handle,'GETFREESYSTEMRESOURCES');
  if  Assigned(GetFSR) then  //Test result for nil
    asm
      //Manually push onto the stack type of resource to be checked first
      push  SysResource
      //Load routine address into EDX
      mov   edx, [GetFSR]
      //Call routine
      call  QT_Thunk
      //Assign result to the function
      mov   @Result, ax
    end
  else
    raise EFOpenError.Create('GetProcAddress16 failed!');
end;

initialization

//Check Platform for Windows 9x
if Win32Platform <> VER_PLATFORM_WIN32_WINDOWS then
  raise EThunkError.Create('Flat thunks only supported under Windows 9x');

//Load 16-bit DLL (USER.EXE)
User16Handle:= LoadLibrary16(PChar('User.exe'));

if User16Handle < 32 then
  raise EFOpenError.Create('LoadLibrary16 failed!');

finalization

//Release 16-bit DLL when done
if User16Handle <> 0 then
  FreeLibrary16(User16Handle);

end.