CJKV Information Processing, 2nd Edition

Unicode Encoding Methods

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e Base64 character setTable 4-18.

Value—Decimal Bit array Base64 character—ASCII Hexadecimal

53 1111 1 31

54 1111 2 32

55 11111 3 33

56 111 4 34

57 1111 5 35

58 1111 6 36

59 11111 7 37

60 1111 8 38

61 11111 9 39

62 11111 + 2

63 111111 / 2

e actual binary representation for the values in Table 4-18 correspond to bit arrays of

the same values. For example, the bit array for Value  is “” (), and the bit ar-

ray for Value 63 is “111111” (3).

Because UTF-7 does not blindly apply Base64 transformation to an entire le, stream,

buer, or string, there are some characters—which form a subset of the ASCII character

set—that represent themselves according to ASCII encoding. Table 4-19 lists the charac-

ters that can be directly encoded according to ASCII encoding.

UTF-7 directly encoded charactersTable 4-19.

Characters UCS-2/UTF-16BE encoding form UTF-7 encoding form

’  27 27

(  28 28

)  29 29

,  2 2

-  2 2

.  2 2

/  2 2

0–9  3– 39 3–39

:  3 3

?  3 3

A–Z  41– 5 41–5

a–z  61– 7 61–7

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Chapter 4: Encoding Methods

Table 4-20 lists the optional directly encoded characters of the UTF-7 encoding form.

ey are optional because in some contexts these characters may not be reliably transmit-

ted. It is up to ...