_AllocHand( ) API Library Routine Example

In The following example, a character is replicated in memory supplied by _AllocHand( ). The API function REPLTOMH( ) below returns the memory handle to Visual FoxPro. From Visual FoxPro the memory handle is passed to API functions, which expect a memory handle argument (passed as an integer, "I").

Visual FoxPro Code

SET LIBRARY TO ALLOCHAN
mh = REPLTOMH("x", 120)
? MHTOFOX(mh)
? LEN(MHTOFOX(mh))
? MHTOFOX(mh)
= FREEMH(mh)

C Code

#include <pro_ext.h>

//   Replicate char argument to memory allocated with _AllocHand().
//   Return the memory handle to Visual FoxPro.
void FAR replToMH(ParamBlk FAR *parm)
{
   char FAR *rep;
   char c = *(char *) _HandToPtr(parm->p[0].val.ev_handle);
   MHANDLE mh;

   if ((mh = _AllocHand((int) parm->p[1].val.ev_long + 1)) == 0)
   {
      _Error(182);  // "Insufficient memory"
   }
   _HLock(mh);
   rep = _HandToPtr(mh);
   _MemFill(rep, c, (int) parm->p[1].val.ev_long);
   rep[parm->p[1].val.ev_long] = '\0';  // null terminate
   _HUnLock(mh);

   _RetInt(mh, 10);
}

//   Returns characters in memory handle.
//   Argument in call from Visual FoxPro
//   must be a valid Visual FoxPro memory handle.
void FAR MHToFoxString(ParamBlk FAR *parm)
{
   char FAR *string;
   MHANDLE mh = parm->p[0].val.ev_long;

   _HLock(mh);
   string = _HandToPtr(mh);
   _RetChar(string);
   _HUnLock(mh);
}

//   Frees memory handle.  Argument in call from
//   Visual FoxPro must be a valid
//   Visual FoxPro memory handle.
void FAR freeMH(ParamBlk FAR *parm)
{
   _FreeHand((MHANDLE) parm->p[0].val.ev_long);
}

FoxInfo myFoxInfo[] = {
   {"REPLTOMH", (FPFI) replToMH, 2, "C,I"},
   {"MHTOFOX", (FPFI) MHToFoxString, 1, "I"},
   {"FREEMH", (FPFI) freeMH, 1, "I"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};