RFC 2045中规定base64编码结果中一行的字符个数不能超过76个
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在网上看到一种说法:“RFC 822中规定了base64编码结果中一行的字符个数不能超过76个”。可是我在RFC 822中没有找到。后来在RFC 2045中找到了,摘录出相关句子列在下面:
RFC 2045 Multipurpose Internet Mail Extensions (MIME)
(http://www.ietf.org/rfc/rfc2045.txt)
(Soft Line Breaks) The Quoted-Printable encoding REQUIRES that encoded lines be no more than 76 characters long. If longer lines are to be encoded with the Quoted-Printable encoding, "soft" line breaks.
The 76 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
Encoded lines must not be longer than 76 characters, not counting the trailing CRLF. If longer lines are found in incoming, encoded data, a robust implementation might nevertheless decode the lines, and might report the erroneous encoding to the user.
Table 1: The Base64 Alphabet
Value Encoding Value Encoding Value Encoding Value Encoding
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
The encoded output stream must be represented in lines of no more
than 76 characters each. All line breaks or other characters not
found in Table 1 must be ignored by decoding software. In base64
data, characters other than those in Table 1, line breaks, and other
white space probably indicate a transmission error, about which a
warning message or even a message rejection might be appropriate
under some circumstances.
由此也可以看出,base64只是一种编码方法,并不是在任何情况下base64编码结果中一行的字符个数都不能超过76个。仅在Internet的相关应用中使用的base64编码,比如MIME中,才有这样的要求。
RFC 2045 Multipurpose Internet Mail Extensions (MIME)
(http://www.ietf.org/rfc/rfc2045.txt)
(Soft Line Breaks) The Quoted-Printable encoding REQUIRES that encoded lines be no more than 76 characters long. If longer lines are to be encoded with the Quoted-Printable encoding, "soft" line breaks.
The 76 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
Encoded lines must not be longer than 76 characters, not counting the trailing CRLF. If longer lines are found in incoming, encoded data, a robust implementation might nevertheless decode the lines, and might report the erroneous encoding to the user.
Table 1: The Base64 Alphabet
Value Encoding Value Encoding Value Encoding Value Encoding
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
The encoded output stream must be represented in lines of no more
than 76 characters each. All line breaks or other characters not
found in Table 1 must be ignored by decoding software. In base64
data, characters other than those in Table 1, line breaks, and other
white space probably indicate a transmission error, about which a
warning message or even a message rejection might be appropriate
under some circumstances.
由此也可以看出,base64只是一种编码方法,并不是在任何情况下base64编码结果中一行的字符个数都不能超过76个。仅在Internet的相关应用中使用的base64编码,比如MIME中,才有这样的要求。
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