PenDataFromBuffer 

2.0     

Creates a HPENDATA object from serial data in a buffer. The buffer must have been previously written by the PenDataToBuffer232HAKC function.

LONG PenDataFromBuffer( LPHPENDATA lphpndt, UINT gmemFlags, LPBYTE lpBuffer, LONG cbBuf, LPDWORD lpdwState )

Parameters

lphpndt

Pointer to an uninitialized HPENDATA handle. If PenDataFromBuffer returns successfully, lphpndt points to a new HPENDATA object containing a copy of the serial points.

gmemFlags

Flag that specifies whether or not the Windows GlobalAllocF12W9. function should create a shared memory object when the pen data object is created. This should be either 0 or GMEM_DDESHARE. The GMEM_MOVEABLE and GMEM_ZEROINIT flags are added to this value and other GMEM_ flags are ignored.

lpBuffer

Pointer to a byte buffer containing serial data.

cbBuf

Size of the buffer, which must be at least 64 bytes in size. If the buffer serves as an intermediate holding area, it need not be as large as the final HPENDATA object. To create the object, the application must call PenDataFromBuffer successively, each time reading a new section of data into the buffer that lpBuffer points to before the call. The example below illustrates this technique by filling an HPENDATA object in stages, reading data from a file in cbBuf increments.

lpdwState

Address of a DWORD variable used by the system to maintain the transfer state. The DWORD variable must be initialized to 0 before the first call to PenDataFromBuffer. Between successive calls to PenDataFromBuffer, the application must not alter the value that lpdwState points to. lpdwState can be NULL to signify that the buffer contains the entire data set for the HPENDATA object. This implies that subsequent calls to PenDataFromBuffer are not necessary.

Return Value

If successful, PenDataFromBuffer returns the number of bytes transferred from the buffer. If the size of the pen data is larger than the buffer, the return value is equal to the buffer size passed in cbBuf. A value of 0 indicates no more data to transfer. If there is an error, one of the following negative values is returned:

Comments

The data being provided by the application must have been previously written by the PenDataToBuffer232HAKC function. The application cannot modify this data in any way. Embedded values within the first 64 bytes provide information to PenDataFromBuffer about the size of the pen data.

PenDataFromBuffer creates an HPENDATA object and provides a handle to it. The application must destroy the object when finished. The lphpndt argument points to a valid HPENDATA handle only if the function returns PDR_OK.

While this function is reconstituting the HPENDATA object, the application must not attempt to use it in any way because it will be invalid until the last buffer is read.

Example

The following example shows how to create a HPENDATA object from a file (hfile) that has already been opened for reading. Before reading the pen data, its length is retrieved from the file:

#define cbBufMax 1024

HPENDATA NEAR PASCAL ReadPenData( HFILE hfile )

{ 

     HPENDATA          hpndt = NULL;

     LONG              cb, cbRead, cbHpndt;

     BYTE              lpbBuf[cbBufMax];       // Buffer

     DWORD       dwState = 0L;                 // Must initialize to 0

     if (!hfile

           || (cb = _lread(hfile, &cbHpndt, sizeof(DWORD))) == HFILE_ERROR

           || cb != sizeof(LONG))

                 return NULL;

     while (cbHpndt > 0)

     { 

           if ((cbRead = _lread( hfile, lpbBuf, min(cbHpndt, cbBufMax )))

                 == HFILE_ERROR

                 || PenDataFromBuffer( &hpndt, 0, lpbBuf,

                                                 cbBufMax, &dwState ) < 0)

           { 

                 if (hpndt)

                       DestroyPenData( hpndt );

                 return NULL;

           }

           cbHpndt -= cbRead;

     }

     return hpndt;

}

See Also