This class encodes and decodes data in Base64 format. This is MIME encoding. We translate a whole stream at once, taking a Stream as input and giving one as output. Returns a whole stream for the caller to use.
0 A 17 R 34 i 51 z
1 B 18 S 35 j 52 0
2 C 19 T 36 k 53 1
3 D 20 U 37 l 54 2
4 E 21 V 38 m 55 3
5 F 22 W 39 n 56 4
6 G 23 X 40 o 57 5
7 H 24 Y 41 p 58 6
8 I 25 Z 42 q 59 7
9 J 26 a 43 r 60 8
10 K 27 b 44 s 61 9
11 L 28 c 45 t 62 +
12 M 29 d 46 u 63 /
13 N 30 e 47 v
14 O 31 f 48 w (pad) =
15 P 32 g 49 x
16 Q 33 h 50 y
Outbound: bytes are broken into 6 bit chunks, and the 0-63 value is converted to a character. 3 data bytes go into 4 characters.
Inbound: Characters are translated in to 0-63 values and shifted into 8 bit bytes.

(See: N. Borenstein, Bellcore, N. Freed, Innosoft, Network Working Group, Request for Comments: RFC 1521, September 1993, MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies. Sec 6.2)

By Ted Kaehler, based on Tim Olson's Base64Filter.

	conversion	top
	mimeDecode Convert a stream in base 64 with only a-z,A-Z,0-9,+,/ to a full byte stream of characters. Reutrn a whole stream for the user to read.
	mimeDecodeToByteArray Convert a stream in base 64 with only a-z,A-Z,0-9,+,/ to a full ByteArray of 0-255 values. Reutrn a whole stream for the user to read.
	mimeEncode Convert from data to 6 bit characters.
	nextValue The next six bits of data char from the mimeStream, or nil. Skip all other chars

	as yet unclassified	top
	decodeInteger: Decode the MIME string into an integer of any length
	encodeInteger: Encode an integer of any length and return the MIME string
	example Base64MimeConverter example
	exampleFor: Provide a MethodCall with a valid example of aSelector, ready to run. If 'all', provide all tests we know about for SUnit tests. When 'all', each will be a Verifier, with an expected answer. Returns a list of MethodCalls, Verifiers, or VerifierOfPropertys.
	initialize Object initialize
	mimeDecodeToBytes: Return a RWBinaryOrTextStream of the original ByteArray. aStream has only 65 innocuous character values. aStream is not binary. (See class comment). 4 bytes in aStream goes to 3 bytes in output.
	mimeDecodeToChars: Return a ReadWriteStream of the original String. aStream has only 65 innocuous character values. It is not binary. (See class comment). 4 bytes in aStream goes to 3 bytes in output.
	mimeEncode: Return a ReadWriteStream of characters. The data of aStream is encoded as 65 innocuous characters. (See class comment). 3 bytes in aStream goes to 4 bytes in output.