Added base64 encoding and decoding

atob.bm

@@ -0,0 +1,43 @@
+Function atob$ (strng As String)
+    Const B64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+    Dim c1 As _Unsigned _Byte
+    Dim c2 As _Unsigned _Byte
+    Dim c3 As _Unsigned _Byte
+    Dim t1 As _Unsigned _Byte
+    Dim t2 As _Unsigned _Byte
+    Dim t3 As _Unsigned _Byte
+    Dim t4 As _Unsigned _Byte
+    Dim i As Long
+    Dim Buffer As String
+
+    For i = 1 To Len(strng) Step 3
+        c1 = Asc(Mid$(strng, i, 1))
+        t1 = _SHR((c1), 2)
+        Buffer = Buffer + Mid$(B64, t1 + 1, 1)
+        If Len(strng) >= i + 1 Then
+            c2 = Asc(Mid$(strng, i + 1, 1))
+            t2 = (_SHL((c1 And &B00000011), 4)) Or (_SHR((c2), 4))
+            Buffer = Buffer + Mid$(B64, t2 + 1, 1)
+        Else
+            t2 = (_SHL((c1 And &B00000011), 4))
+            Buffer = Buffer + Mid$(B64, t2 + 1, 1)
+            Buffer = Buffer + "=="
+            atob$ = Buffer
+            Exit Function
+        End If
+        If Len(strng) >= i + 2 Then
+            c3 = Asc(Mid$(strng, i + 2, 1))
+            t3 = (_SHL((c2 And &B00001111), 2)) Or (_SHR((c3), 6))
+            Buffer = Buffer + Mid$(B64, t3 + 1, 1)
+            t4 = c3 And &B00111111
+            Buffer = Buffer + Mid$(B64, t4 + 1, 1)
+        Else
+            t3 = (_SHL((c2 And &B00001111), 2))
+            Buffer = Buffer + Mid$(B64, t3 + 1, 1)
+            Buffer = Buffer + "="
+            atob$ = Buffer
+            Exit Function
+        End If
+    Next
+    atob$ = Buffer
+End Function

btoa.bm

@@ -0,0 +1,19 @@
+Function btoa$ (s As String)
+    Const B64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+    Dim c1 As _Byte
+    Dim c2 As _Byte
+    Dim c3 As _Byte
+    Dim c4 As _Byte
+    Dim i As Long
+    Dim As String Buffer
+    For i = 1 To Len(s) Step 4
+        c1 = InStr(B64, Mid$(s, i + 0, 1)) - 1
+        c2 = InStr(B64, Mid$(s, i + 1, 1)) - 1
+        c3 = InStr(B64, Mid$(s, i + 2, 1)) - 1
+        c4 = InStr(B64, Mid$(s, i + 3, 1)) - 1
+        If c2 > -1 Then Buffer = Buffer + Chr$(((c1 * 4 + c2 \ 16) And 255))
+        If c3 > -1 Then Buffer = Buffer + Chr$(((c2 * 16 + c3 \ 4) And 255))
+        If c4 > -1 Then Buffer = Buffer + Chr$(((c3 * 64 + c4) And 255))
+    Next i
+    btoa$ = Buffer
+End Function