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_MemCmp( ) API Library Routine

  • Article

Compares two length byte memory areas.

int _MemCmp(void FAR *ptr1, void FAR *ptr2, unsigned int length)
void FAR *ptr1;            /* First point to start compare. */
void FAR *ptr2;            /* Second point to start compare. */
unsigned int length;         /* How much to compare in bytes. */

Remarks

_MemCmp( ) compares each byte in the two areas, starting with the leftmost byte in each, until two bytes don't match. _MemCmp( ) returns 0 if all bytes in the areas match, a positive number if the first unmatched byte in the first area is greater than the corresponding byte in the second area, or a negative number if the first unmatched byte in the second area is greater than the corresponding byte in the first area.

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 uses _MemCmp( ) to compare two character parameters up to the length of the first unmatched byte.

Visual FoxPro Code

SET LIBRARY TO MEMCMP  
? MEMCMP("Hello, world.", "Hello, world.")  && returns 0
? MEMCMP("Hello, world.", "Hello, wurld.")  && returns non-0

C Code

#include <pro_ext.h>

#define min(a, b) ((a) < (b) ? (a) : (b))

FAR Example(ParamBlk FAR *parm)
{
   int LenToCmp, RetValue;

   LenToCmp = min(parm->p[0].val.ev_length, parm->p[1].val.ev_length);

   _HLock(parm->p[0].val.ev_handle);
   _HLock(parm->p[1].val.ev_handle);

   RetValue = _MemCmp(_HandToPtr(parm->p[0].val.ev_handle),
      _HandToPtr(parm->p[1].val.ev_handle), LenToCmp);

   _RetInt(RetValue, 10); // does return control here

   _HUnLock(parm->p[0].val.ev_handle);
   _HUnLock(parm->p[1].val.ev_handle);
}

FoxInfo myFoxInfo[] = {
   {"MEMCMP", (FPFI) Example, 2, "C,C"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};

See Also

_MemFill( ) API Library Routine | _MemMove( ) API Library Routine | Accessing the Visual FoxPro API