Extending/Merging VB Arrays

Question

I have a class with a public array of byte(). Lets say its Public myBuff as byte() Events within the class get chunks of data in byte() array. How do i tell the event code to stick the get chunk on the end. Lets say Private Sub GetChunk Dim chunk as byte ... get stuff in chunk Me.myBuff += chunk (stick chunk on end of public array End sub

Or am I totally missing the point?

Answer 1

if i remember right, in vb you want to redim with preserve to grow an array.

Answer 2

You'll be constantly using the ReDim keyword, which is extremely inefficient.

Are you using .Net? If so, consider using a System.Collections.Generic.List(Of Byte) instead. You can use it's .AddRange() method to append your bytes, and it's .ToArray() method to get an array back out if you really need one.

Answer 3

Your question doesn't seem to be very clear. You should probably not have the array of bytes as public. It should probably be private and you should provide a set of public functions that allow users of the class to perform operations against the array.

Answer 4

I think you might be looking for something other then an array. If you are trying to gradually extend the amount of data frequently, you should use a dynamic data structure such asArrayList. This has an Add method which adds the specific object or value to the array without concerns for space. It also has a nifty ToArray() method that you can use.

If you are trying to use an array for specific reasons (performance, I guess), use ReDim Preserve array(newSize).

Answer 5

If the array is small, and new data is infrequently added, an easy way would be to:

public BufferSize as long 'or you can just use Ubound(mybuff), I prefer a tracker var tho
public MyBuff

private sub GetChunk()
dim chunk as byte
'get stuff
BufferSize=BufferSize+1

redim preserve MyBuff(buffersize)
mybuff(buffersize) = chunk
end sub

if chunk is an array of bytes, it would look more like:

buffersize=buffersize+ubound(chunk) 'or if it's a fixed-size chunk, just use that number
redim preserve mybuff(buffersize)
for k%=0 to ubound(chunk) 'copy new information to buffersize
  mybuff(k%+buffersize-ubound(chunk))=chunk(k%)
next

if you will be doing this frequently (say, many times per second) you'd want to do something like how the StringBuilder class works:

public BufSize&,BufAlloc& 'initialize bufalloc to 1 or a number >= bufsize
public MyBuff() as byte

sub getdata()
bufsize=bufsize+ubound(chunk)
if bufsize>bufalloc then
  bufalloc=bufalloc*2
  redim preserve mybuff(bufalloc)
end if
for k%=0 to ubound(chunk) 'copy new information to buffersize
  mybuff(k%+bufsize-ubound(chunk))=chunk(k%)
next
end sub

that basically doubles the memory allocated to mybuf each time the pointer passes the end of the buffer. this means much less shuffling around of memory.