_HLock( ) API Library Routine 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. Because Visual FoxPro may decide to reorganize memory during the call to _PutStr( ), to insure proper execution, the example locks the memory handle with _HLock( ). The example also calls _HUnLock( ) at the end, because the performance of Visual FoxPro can be adversely affected by locked memory handles.

Visual FoxPro Code

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

C 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[] = {
   {"HLOCK", (FPFI) Example, 1, "C"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};