_AllocMemo( ) API Library Routine

Visual FoxPro 9.0 SP2

_AllocMemo( ) API Library Routine


long _AllocMemo(Locator FAR fld, long size) Locator FAR fld; /* Pointer to locator that defines the memo field. / long size; / Size of allocated space in bytes. */

Remarks

When _AllocMemo( ) is successful, it returns the location in the file to begin writing; otherwise, it returns – 1.

Caution
Writing more than size bytes causes memo file corruption.

If you plan to replace a memo field using direct methods, be sure your routine calls _AllocMemo( ) before writing to the memo file, even if the new value is the same length or smaller than the original. This prevents problems in multiuser situations. _AllocMemo( ) reuses the previously allocated space when it's safe to do so.

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 creates new memo field contents.

Visual FoxPro Code

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SET LIBRARY TO ALLOMEMO CREATE TABLE wMemo (memoField M) APPEND BLANK = NewMemo(@MemoField, "Hello, World.") APPEND BLANK = NewMemo(@MemoField, "Isn't this fun?")

C Code

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#include <pro_ext.h> FAR newMemo(ParamBlk FAR parm) { Locator FAR memoFldLoc; FCHAN fchMemo; int memoLen; long loc; if ((fchMemo = _MemoChan(-1)) == -1) { _UserError("_MemoChan() failed"); } memoFldLoc = &parm->p[0].loc; memoLen = parm->p[1].val.ev_length; if ((loc = _AllocMemo(memoFldLoc, memoLen)) == -1) { _UserError("_AllocMemo() failed"); } _FSeek(fchMemo, loc, FS_FROMBOF); _HLock(parm->p[1].val.ev_handle); _FWrite(fchMemo, _HandToPtr(parm->p[1].val.ev_handle), memoLen); _HUnLock(parm->p[1].val.ev_handle); } FoxInfo myFoxInfo[] = { {"NEWMEMO", (FPFI) newMemo, 2, "R,C"}, }; FoxTable _FoxTable = { (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo };

Copy Code

#include <pro_ext.h>
FAR newMemo(ParamBlk FAR *parm)
{
   Locator FAR *memoFldLoc;
   FCHAN fchMemo;
   int memoLen;
   long loc;
   if ((fchMemo = _MemoChan(-1)) == -1)
   {
      _UserError("_MemoChan() failed");
   }
   memoFldLoc = &parm->p[0].loc;
   memoLen = parm->p[1].val.ev_length;
   if ((loc = _AllocMemo(memoFldLoc, memoLen)) == -1)
   {
      _UserError("_AllocMemo() failed");
   }
   _FSeek(fchMemo, loc, FS_FROMBOF);
   _HLock(parm->p[1].val.ev_handle);
   _FWrite(fchMemo, _HandToPtr(parm->p[1].val.ev_handle), memoLen);
   _HUnLock(parm->p[1].val.ev_handle);
}
FoxInfo myFoxInfo[] = {
   {"NEWMEMO", (FPFI) newMemo, 2, "R,C"},
};
FoxTable _FoxTable = {
   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};

_AllocMemo( ) API Library Routine

Remarks

Example

Visual FoxPro Code

C Code

See Also

Reference

Concepts

Other Resources