delphi - Call and Reuse the DLL functions dynamically -

i have created dll file functions , wish reuse in program multiple times in different functions. access-violation error comes after 2nd function of program when calls same dll functions.

i'm using getprocaddress. example:

function xyz:boolean var    dllhandle : cardinal;    enbfstr : tenbfstr;    strtohex : tstrtohex;    encodeddata , hexstring : unicodestring;     begin      dllhandle := loadlibrary('utilities.dll') ;      if dllhandle <> 0      begin         encodeddata:='sample';         @enbfstr := getprocaddress(dllhandle, 'encodeblowfishstring') ;         @strtohex := getprocaddress(dllhandle, 'unistrtounihexstr') ;         if assigned (enbfstr)            encodeddata:=enbfstr('key','text') ; //sample replaced          if assigned (strtohex )            hexstring :=strtohex(encodeddata) ; //call function          freelibrary(dllhandle) ;  end; 

there other functions loading library , calling these dll functions multiple times. also, within same procedure/function, calling these dll functions multiple times in (if else) conditions.

in earlier part of program, have tried check dll file present. also, tried directly load functions alternative:

function encodeblowfishstring (const key:unicodestring; const decodedstring:unicodestring; ): unicodestring; stdcall; external 'utilities.dll' name 'encodeblowfishstring';  function unistrtounihexstr(const astring:unicodestring): unicodestring; stdcall; external 'utilities.dll'; 

you breaking rules of memory allocation dlls. return value allocated callee deallocated caller. 2 solutions:

1. use sharemem described in comment @ top of new library project.
2. use standard interoperability techniques ensure allocation , deallocation happens in same module.

as aside wasteful load , unload dll each time want use it. load dll once only.

furthermore point out encryption operates on binary data , in view storing world of pain working instead text.