【列表3.5】交叉平臺庫接口單元。
{ HelloDynmX - Cross-platform dynamic library interface
unit HelloDynmX;
interface
procedure SayHello
implementation
uses SysUtils,
{$IFDEF LINUX}
   Libc
{$ELSE}
   Windows
{$ENDIF}
;
const
  {$IFDEF LINUX}
    STR_LIB_NAME= 'libhello.so.1';
    LibnandleNull =nil;
  {$ ELSE}
    STR_LIB_NAME = 'sample';
    LIbHandleNull = 0;
  {$ENDIF}

  // function names in library
  STR_HELLO_NAME = 'SayHello';
type
  {$IFDEF LINUX}
    TLibHandle = Pointer;
  {$ ELSE}
    TLIbHandle = HModule;
 {$ENDIF}
  HelloProc = procedure;
    {$IFDEF LINUX} cdecl; {$ELSE} stdeall: {$ENDIF}
const
  LibHandle : TLIbHandle = LIbHandleNull;
function GetLIbraryHandle : TLibHandle;
begin
  if libHandle =libHandleNull then
  begin
    {$IFDEF LINUX}
      libHandle :=dlopen (STR_LIB_HAME, RTLD_LAZY);
    {$ELSE}
      libHandle := LoadLIbrary (STR_LIB_NAME);
    {$ENDIF}
    if libHandle = libHandleNun then raise Exception.CreateFmt
        ('Unable to open library "%s"', [STR_LIB_NAME]);
  end:
  Result := libHandle;
end;

function GetLibrarySymbol (const fName: String): Pointer;
var
  bErr : boolean;
begin 
{$IFDEF LINUX}
    dlerror; // call to clear error code
    Result :=dlsym (GetLibraryHandle, PChar(fName));
    bErr := (dlerror <> nil);
  {$ELSE}
    Result :=GetProcAddress (GetLibraryHandle, PChar(fName));
    bErr := (Result = nil );
  {$ENDIF}
  if bErr then
    raise Exception.CreateFmt
       ('Unable to locate symbol "%s" in library "%s".',
         [STR_LIB_NAME, fName]);
end;

procedure SayHello;
const
  HelloPtr : HelloProc = nil ;
begin
  if not Assigned (HelloPtr)  then
    HelloPtr := GetLIbrarySymbol (STR_HELLO_NAME);
  HelloPtr;
  dICIose (LibHandle);
  LibHandle := LibHandleNull;
end;
initialization
  // no initialization--needed for finalization
finalization
   if libHandle <> LibHandleNull then
   begin 
     {$IFDEF LINUX}
       if dlclose (libHandle) =-1  then
     {$ELSE}
       if not FreeLlbrary (libHandle) then
     {$ENDIF}
         raise Exception.CreateFmt
           ('Error closing library "%s".', [STR_LIB_NAME]);
   end;
 end.