winapi - Calling Win32 DLL from C++ -

i new dll world. have been given win32 dll has lot of functions. need call these dll functions c++

i want call createnewscanner creates new scanner object , results in c++. function mentioned in dll is:

bool createnewscanner(newscanner *newscan); 

and newscanner struct, below,

// structure newscanner defined in "common.h" . typedef struct{   byte host_no; // <- host_no =0   long time; // <- command timeout (in seconds)   byte status; // -> host adapter status   handle obj; // -> object handle scanner }newscanner; 

how call function? started c++ , here managed,

#include <iostream> #include <windows.h> using namespace std; int main(){   hinstance hinstance;       if(!(hinstance=loadlibrary("winscanner.dll"))){       cout << "could not load library" << endl;           }   /* pointer function in dll*/   farproc handle = getprocaddress(hmodule(hinstance), "createnewscanner");   if(!handle){     // handle error     freelibrary(hinstance);     return "-1";   }else{         // call function     //how call here??   } } 

first of all, return "-1" no good. expected return integer. surely mean return -1.

now question. instead of declaring function pointer farproc, it's easier declare function pointer type.

typedef bool (*createnewscannerproc)(newscanner*); 

then call getprocaddress this:

hmodule hlib = loadlibrary(...); // loadlibrary returns hmodule , not hinstance // check hlib null  createnewscannerproc createnewscanner =      (createnewscannerproc) getprocaddress(hlib, "createnewscanner"); if (createnewscanner == null)     // handle error  // can call function newscanner newscan; bool retval = createnewscanner(&newscan); 

having said of that, library come header file (yours should include it) , .lib file load-time linking. make sure pass .lib file linker , can this:

#include "nameoftheheaderfilegoeshere.h" .... newscanner newscan; bool retval = createnewscanner(&newscan); 

no need mess around loadlibrary, getprocaddress , on.