Buffer

Applies to:

Description

Sets or returns the contents of a control's current record buffer. The record buffer is the raw record data retrieved by Pervasive.SQL.

Syntax

object.Buffer(short alignment) 

The Buffer property syntax has these parts:

Remarks

Data is read from and written to the current record buffer. On a read operation, this property returns an OLE Variant containing a byte array representation of the current record buffer. On a write operation, it takes an OLE Variant which contains a byte array to be written to the current record buffer. Changes made to this property are not saved in the Btrieve file until a successful Update or Insert method is invoked.

The buffer that is returned is the single record buffer only; it will not contain the contents of the status buffer after a Stat call, nor will it contain an extended operations record buffer after an extended operations call. This information is available through other properties and methods (see Stat, RowColumnValue, and RowPosition). The Clear method will clear this buffer.

Certain programming environments allow or require specific byte alignment for structured variables. The alignment parameter enables you to specify the byte alignment to be used for individual fields within the record.

This property is not available at design time.

Public Type SAFEARRAYBOUNDS 
  cElements As Long 
  lLbound As Long 
End Type 
Public Type SAFEARRAY 
  cDims As Integer 
  fFeatures As Integer 
  cbElements As Long 
  cLocks As Long 
  pvData As Long 
  Bounds(0) As SAFEARRAYBOUNDS 
End Type 
Public Type Buffer 
  msa_desc As String * 34 
  population As Long 
  prev_population As Long 
End Type 
Declare Sub CopyMemory Lib "KERNEL32" Alias _ 
"RtlMoveMemory" (pDest As Any, pSrc As Any, ByVal _ 
ByteLen As Long) 
Declare Function VarPtrArray Lib "msvbvm50.dll" _ 
Alias "VarPtr" (Ptr() As Any) As Long 
Public Sub ReadData() 
  Dim i as integer 
  Dim dataArray() as Buffer 
  Dim byteArray() as Byte 
  VAccess1.Open 
  VAccess1.GetFirst 
   
  Redim dataArray(VAccess1.TotalRecords) 
   
  For i = 0 to VAccess1.TotalRecords-1 
    ByteArray = VAccess1.Buffer(4) 
    DataArray(i) = GetBuffer(byteArray) 
    VAccess1.GetNext 
  Next i 
End Sub 
Public Function GetBuffer(bufferArray() As Byte) _
as Buffer 
  Dim status As Integer 
  Dim saPtr As Long 
  Dim saStruct As SAFEARRAY 
  Dim record as Buffer 
      
  'get the address of safearray structure 
  CopyMemory saPtr, ByVal 
VarPtrArray(bufferArray),_ 4 
  'copy the safearray structure 
  CopyMemory saStruct, ByVal saPtr, Len(saStruct) 
  'copy the data array into our structure 
  CopyMemory record, ByVal saStruct.pvData, 
BufferSize(saStruct) 
  GetBuffer = record 
End Function 

See Also

Affected by: Clear, GetDirect, GetEqual, GetGreaterOrEqual, GetLessOrEqual, GetFirst, GetPrevious, GetNext, GetLast, StepFirst, StepPrevious, StepNext, StepLast, Percentage.