September 2017 Update

Task/CRC-32/Visual-Basic-.NET/crc-32-1.visual

@@ -0,0 +1,29 @@
+Public Class Crc32
+
+    ' Table for pre-calculated values.
+    Shared table(255) As UInteger
+
+    ' Initialize table
+    Shared Sub New()
+        For i As UInteger = 0 To table.Length - 1
+            Dim te As UInteger = i ' table entry
+            For j As Integer = 0 To 7
+                If (te And 1) = 1 Then te = (te >> 1) Xor &HEDB88320UI Else te >>= 1
+            Next
+            table(i) = te
+        Next
+    End Sub
+
+    ' Return checksum calculation for Byte Array,
+    '  optionally resuming (used when breaking a large file into read-buffer-sized blocks).
+    ' Call with Init = False to continue calculation.
+    Public Shared Function cs(BA As Byte(), Optional Init As Boolean = True) As UInteger
+        Static crc As UInteger
+        If Init Then crc = UInteger.MaxValue
+        For Each b In BA
+            crc = (crc >> 8) Xor table((crc And &HFF) Xor b)
+        Next
+        Return Not crc
+    End Function
+
+End Class