FillMemory Function

Declare Sub FillMemory Lib "kernel32.dll" Alias "RtlFillMemory" (Destination As Any, ByVal Length As Long, ByVal Fill As Byte)

Platforms

Windows 95: Supported.
Windows 98: Supported.
Windows NT: Requires Windows NT 3.1 or later.
Windows 2000: Supported.
Windows CE: Not Supported.

Description & Usage

FillMemory fills a location in memory with a certain value. The function does this by setting each byte starting at the given memory location to the desired value. The memory location is identified by a pointer to the memory address.

Return Value

FillMemory does not return a value.

Visual Basic-Specific Issues

A pointer to any variable can be automatically generated merely by passing that variable as Destination. However, if either a String or a Long holding the desired memory address is passed, the ByVal keyword must preceed it. See the example below for a demonstration.

Parameters

Destination: A pointer to the location in memory (often the memory address of a variable) to begin filling with a certain value.
Length: The number of memory bytes, beginning with the address identified by Destination, to fill.
Fill: The byte value to set each byte in the desired memory location to.

Example

' This code is licensed according to the terms and conditions listed here.

' Initialize all the elements in an array of bytes to the value 76.  Also
' set each character in a 20-character string to the character "X".
Dim bytearray(0 To 9) As Byte  ' array of 10 bytes
Dim bytestring As String  ' string to fill
Dim c As Integer  ' counter variable

' Fill the memory at bytearray() in order to initialize its members to 76.  Note that, to
' identify the pointer to bytearray()'s memory, it is passed as normal.
FillMemory bytearray(0), 10, 76  ' fill 10 bytes to the byte value 76
' Display the results to verify that it worked.
For c = 0 To 9  ' loop through each element
  Debug.Print bytearray(c);  ' each value displayed will be 76
Next c

' Now fill a 20-character string with "X" (using its ASCII code).  Note how, in Visual
' Basic, the ByVal keyword must preceed the string in this case.
bytestring = Space(20)  ' make the string 20 characters long
FillMemory ByVal bytestring, 20, Asc("X")  ' set the contents to a bunch of "X"'s
' Display the results to verify that it worked.
Debug.Print bytestring  ' will be twenty X's