Public Function calc_crc(ByRef Buffer() As Byte, Size_Less_One As Integer) As Long
Dim A As Long, B As Long, crcc As Long, i As Integer
Dim lcl As Byte
Dim C As Long
crcc = 65535
For i = 0 To Size_Less_One
A = 0
B = 0

lcl = CByte(Buffer(i))
'A = crcc Xor (lcl * 256)
A = lcl * 16
A = A * 16

A = A Xor crcc

B = A
'A = (((A And &HF000) / 16) Xor B)
A = A And &HF000
A = A \ 16
A = A Xor B

B = A
C = B
' B = ((B / 256) And &HFF) + ((B And &HFF) * 256)
B = (B \ 256)
C = (C And &HFF) * 256
B = B + C


A = A And &HFF00
A = (A \ 8) + ((A And 7) * 8192)
B = B Xor A
A = A \ 2
C = A
' A = ((A / 256) And &HFF) + ((A And &HFF) * 256)
A = (A \ 256) And &HFF
C = (C And &HFF) * 256
A = A + C


A = (A And &HF000) Xor B
crcc = A And &HFFFF
Next i
calc_crc = crcc

End Function