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26
27 __all__ = [
28 'base64_len',
29 'body_decode',
30 'body_encode',
31 'decode',
32 'decodestring',
33 'encode',
34 'encodestring',
35 'header_encode',
36 ]
37
38 import re
39
40 from binascii import b2a_base64, a2b_base64
41 from email.utils import fix_eols
42
43 CRLF = '\r\n'
44 NL = '\n'
45 EMPTYSTRING = ''
46
47 MISC_LEN = 7
49
50
51
52 def base64_len(s):
54 """Return the length of s when it is encoded with base64."""
55 groups_of_3, leftover = divmod(len(s), 3)
56 n = groups_of_3 * 4
59 if leftover:
60 n += 4
61 return n
62
63
64
65 def header_encode(header, charset='iso-8859-1', keep_eols=False,
66 maxlinelen=76, eol=NL):
67 """Encode a single header line with Base64 encoding in a given charset.
68
69 Defined in RFC 2045, this Base64 encoding is identical to normal Base64
70 encoding, except that each line must be intelligently wrapped (respecting
71 the Base64 encoding), and subsequent lines must start with a space.
72
73 charset names the character set to use to encode the header. It defaults
74 to iso-8859-1.
75
76 End-of-line characters (\\r, \\n, \\r\\n) will be automatically converted
77 to the canonical email line separator \\r\\n unless the keep_eols
78 parameter is True (the default is False).
79
80 Each line of the header will be terminated in the value of eol, which
81 defaults to "\\n". Set this to "\\r\\n" if you are using the result of
82 this function directly in email.
83
84 The resulting string will be in the form:
85
86 "=?charset?b?WW/5ciBtYXp66XLrIHf8eiBhIGhhbXBzdGHuciBBIFlv+XIgbWF6euly?=\\n
87 =?charset?b?6yB3/HogYSBoYW1wc3Rh7nIgQkMgWW/5ciBtYXp66XLrIHf8eiBhIGhh?="
88
89 with each line wrapped at, at most, maxlinelen characters (defaults to 76
90 characters).
91 """
92 if not header:
94 return header
95
96 if not keep_eols:
97 header = fix_eols(header)
98
99 base64ed = []
102 max_encoded = maxlinelen - len(charset) - MISC_LEN
103 max_unencoded = max_encoded * 3 // 4
104
105 for i in range(0, len(header), max_unencoded):
106 base64ed.append(b2a_base64(header[i:i+max_unencoded]))
107
108 lines = []
110 for line in base64ed:
111 if line.endswith(NL):
113 line = line[:-1]
114 lines.append('=?%s?b?%s?=' % (charset, line))
116 joiner = eol + ' '
119 return joiner.join(lines)
120
121
122
123 def encode(s, binary=True, maxlinelen=76, eol=NL):
124 """Encode a string with base64.
125
126 Each line will be wrapped at, at most, maxlinelen characters (defaults to
127 76 characters).
128
129 If binary is False, end-of-line characters will be converted to the
130 canonical email end-of-line sequence \\r\\n. Otherwise they will be left
131 verbatim (this is the default).
132
133 Each line of encoded text will end with eol, which defaults to "\\n". Set
134 this to "\r\n" if you will be using the result of this function directly
135 in an email.
136 """
137 if not s:
138 return s
139
140 if not binary:
141 s = fix_eols(s)
142
143 encvec = []
144 max_unencoded = maxlinelen * 3 // 4
145 for i in range(0, len(s), max_unencoded):
146 enc = b2a_base64(s[i:i + max_unencoded])
149 if enc.endswith(NL) and eol <> NL:
150 enc = enc[:-1] + eol
151 encvec.append(enc)
152 return EMPTYSTRING.join(encvec)
153
154
155 body_encode = encode
157 encodestring = encode
158
159
160
161 def decode(s, convert_eols=None):
162 """Decode a raw base64 string.
163
164 If convert_eols is set to a string value, all canonical email linefeeds,
165 e.g. "\\r\\n", in the decoded text will be converted to the value of
166 convert_eols. os.linesep is a good choice for convert_eols if you are
167 decoding a text attachment.
168
169 This function does not parse a full MIME header value encoded with
170 base64 (like =?iso-8895-1?b?bmloISBuaWgh?=) -- please use the high
171 level email.Header class for that functionality.
172 """
173 if not s:
174 return s
175
176 dec = a2b_base64(s)
177 if convert_eols:
178 return dec.replace(CRLF, convert_eols)
179 return dec
180
181
182 body_decode = decode
184 decodestring = decode
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