Converting huge byte array to Long array throws Overflow Exception

Question

First time I am developing the vb 6.0 application I am trying to convert huge Byte Array of size(164999) into Long/Integer Array in VB 6.0 but it gives me an Overflow Error.

my code

Dim tempByteData() As Byte // of size (164999)
Dim lCount As Long

Private Sub Open()
    lCount = 164999 **//here I get the count i.e. 164999**                     
    ReDim tempByteData(lCount - 1)
    For x = 0 To obj.BinaryValueCount - 1
        tempwaveformData(x) = CByte(obj.BinaryValues(x))
    Next
    tempByteData(lCount - 1) = BArrayToInt(tempByteData)   
End Sub

Private Function BArrayToInt(ByRef bArray() As Byte) As Long
    Dim iReturn() As Long
    Dim i As Long

    ReDim iReturn(UBound(bArray) - 1)
    For i = 0 To UBound(bArray) - LBound(bArray)
        iReturn(i) = iReturn(i) + bArray(i) * 2 ^ i
    Next i

    BArrayToInt = iReturn(i)

End Function

what needs to be done so that all Byte Array data is converted into Long/Integer Array or any alternate way than this to stored these byte array so that overflow exception not occurred

Answer 1

Depending on the layout of the 32-bit data in the byte array, you can do a straight memory copy from one array to the other.

This will only work if the data is little endian (normal for Win32 applications/data, but not always guaranteed)

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)

Private Function ByteArrayToLongArray(ByRef ByteArray() As Byte) As Long()
Dim LongArray() As Long
Dim Index As Long

  'Create a Long array big enough to hold the data in the byte array
  'This assumes its length is a multiple of 4.
  ReDim LongArray(((UBound(ByteArray) - LBound(ByteArray) + 1) / 4) - 1)

  'Copy the data wholesale from one array to another
  CopyMemory LongArray(LBound(LongArray)), ByteArray(LBound(ByteArray)), UBound(ByteArray) + 1

  'Return the resulting array
  ByteArrayToLongArray = LongArray
End Function

If however the data is big endian, then you will need to convert each byte at a time:

Private Function ByteArrayToLongArray(ByRef ByteArray() As Byte) As Long()
Dim LongArray() As Long
Dim Index As Long

  'Create a Long array big enough to hold the data in the byte array
  'This assumes its length is a multiple of 4.
  ReDim LongArray(((UBound(ByteArray) - LBound(ByteArray) + 1) / 4) - 1)

  'Copy each 4 bytes into the Long array
  For Index = LBound(ByteArray) To UBound(ByteArray) Step 4
    'Little endian conversion
    'LongArray(Index / 4) = (ByteArray(Index + 3) * &H1000000&) Or (ByteArray(Index + 2) * &H10000&) Or (ByteArray(Index + 1) * &H100&) Or (ByteArray(Index))
    'Big endian conversion
    LongArray(Index / 4) = (ByteArray(Index) * &H1000000&) Or (ByteArray(Index + 1) * &H10000&) Or (ByteArray(Index + 2) * &H100&) Or (ByteArray(Index + 3))
  Next

  'Return the resulting array
  ByteArrayToLongArray = LongArray
End Function

(This example currently breaks if the first byte of each quad is greater than 127 which signifies a negative number.)