_HandToPtr( ) API Library Routine

Visual FoxPro 9.0 SP2

_HandToPtr( ) API Library Routine


void FAR * _HandToPtr(MHANDLE hand) MHANDLE hand; /* Memory handle. */

Remarks

Visual FoxPro may reorganize memory any time control is passed to it or to another routine outside of the current module.

Note
_HandToPtr() doesn't cause memory reorganization. The pointer returned by _HandToPtr() may become invalid any time control is passed back to Visual FoxPro, unless the MHANDLE is locked. Don't keep pointers to unlocked memory handles across an external function call, unless it is documented that the call doesn't cause memory reorganization.

For more information on how to create an API library and integrate it with Visual FoxPro, see Accessing the Visual FoxPro API.

Example

The following example displays its character parameter on the screen. It uses _HandToPtr( ) to translate the memory handle of the API parameter to a C pointer.

Visual FoxPro Code

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SET LIBRARY TO HANDTOPT = HANDTOPTR("Hello, world.") && displays "Hello, world" on screen

C Code

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#include <pro_ext.h> void NullTerminate(Value FAR cVal) { if (!_SetHandSize(cVal->ev_handle, cVal->ev_length + 1)) { _Error(182); // "Insufficient memory" } ((char FAR ) _HandToPtr(cVal->ev_handle))[cVal->ev_length] = '\0'; } FAR Example(ParamBlk FAR parm) { NullTerminate(&parm->p[0].val); _HLock(parm->p[0].val.ev_handle); _PutStr(_HandToPtr(parm->p[0].val.ev_handle)); _HUnLock(parm->p[0].val.ev_handle); } FoxInfo myFoxInfo[] = { {"HANDTOPTR", (FPFI) Example, 1, "C"}, }; FoxTable _FoxTable = { (FoxTable FAR ) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo };

Copy Code

#include <pro_ext.h>
void NullTerminate(Value FAR *cVal)
{
   if (!_SetHandSize(cVal->ev_handle, cVal->ev_length + 1)) 
   {
      _Error(182); // "Insufficient memory"
   }
   ((char FAR *) _HandToPtr(cVal->ev_handle))[cVal->ev_length] = '\0';
}
FAR Example(ParamBlk FAR *parm)
{
   NullTerminate(&parm->p[0].val);
   _HLock(parm->p[0].val.ev_handle);
   _PutStr(_HandToPtr(parm->p[0].val.ev_handle));
   _HUnLock(parm->p[0].val.ev_handle);
}
FoxInfo myFoxInfo[] = {
   {"HANDTOPTR", (FPFI) Example, 1, "C"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};

_HandToPtr( ) API Library Routine

Remarks

Example

Visual FoxPro Code

C Code

See Also

Reference

Other Resources