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920dae64 AT |
1 | """A readline()-style interface to the parts of a multipart message. |
2 | ||
3 | The MultiFile class makes each part of a multipart message "feel" like | |
4 | an ordinary file, as long as you use fp.readline(). Allows recursive | |
5 | use, for nested multipart messages. Probably best used together | |
6 | with module mimetools. | |
7 | ||
8 | Suggested use: | |
9 | ||
10 | real_fp = open(...) | |
11 | fp = MultiFile(real_fp) | |
12 | ||
13 | "read some lines from fp" | |
14 | fp.push(separator) | |
15 | while 1: | |
16 | "read lines from fp until it returns an empty string" (A) | |
17 | if not fp.next(): break | |
18 | fp.pop() | |
19 | "read remaining lines from fp until it returns an empty string" | |
20 | ||
21 | The latter sequence may be used recursively at (A). | |
22 | It is also allowed to use multiple push()...pop() sequences. | |
23 | ||
24 | If seekable is given as 0, the class code will not do the bookkeeping | |
25 | it normally attempts in order to make seeks relative to the beginning of the | |
26 | current file part. This may be useful when using MultiFile with a non- | |
27 | seekable stream object. | |
28 | """ | |
29 | ||
30 | __all__ = ["MultiFile","Error"] | |
31 | ||
32 | class Error(Exception): | |
33 | pass | |
34 | ||
35 | class MultiFile: | |
36 | ||
37 | seekable = 0 | |
38 | ||
39 | def __init__(self, fp, seekable=1): | |
40 | self.fp = fp | |
41 | self.stack = [] | |
42 | self.level = 0 | |
43 | self.last = 0 | |
44 | if seekable: | |
45 | self.seekable = 1 | |
46 | self.start = self.fp.tell() | |
47 | self.posstack = [] | |
48 | ||
49 | def tell(self): | |
50 | if self.level > 0: | |
51 | return self.lastpos | |
52 | return self.fp.tell() - self.start | |
53 | ||
54 | def seek(self, pos, whence=0): | |
55 | here = self.tell() | |
56 | if whence: | |
57 | if whence == 1: | |
58 | pos = pos + here | |
59 | elif whence == 2: | |
60 | if self.level > 0: | |
61 | pos = pos + self.lastpos | |
62 | else: | |
63 | raise Error, "can't use whence=2 yet" | |
64 | if not 0 <= pos <= here or \ | |
65 | self.level > 0 and pos > self.lastpos: | |
66 | raise Error, 'bad MultiFile.seek() call' | |
67 | self.fp.seek(pos + self.start) | |
68 | self.level = 0 | |
69 | self.last = 0 | |
70 | ||
71 | def readline(self): | |
72 | if self.level > 0: | |
73 | return '' | |
74 | line = self.fp.readline() | |
75 | # Real EOF? | |
76 | if not line: | |
77 | self.level = len(self.stack) | |
78 | self.last = (self.level > 0) | |
79 | if self.last: | |
80 | raise Error, 'sudden EOF in MultiFile.readline()' | |
81 | return '' | |
82 | assert self.level == 0 | |
83 | # Fast check to see if this is just data | |
84 | if self.is_data(line): | |
85 | return line | |
86 | else: | |
87 | # Ignore trailing whitespace on marker lines | |
88 | marker = line.rstrip() | |
89 | # No? OK, try to match a boundary. | |
90 | # Return the line (unstripped) if we don't. | |
91 | for i, sep in enumerate(reversed(self.stack)): | |
92 | if marker == self.section_divider(sep): | |
93 | self.last = 0 | |
94 | break | |
95 | elif marker == self.end_marker(sep): | |
96 | self.last = 1 | |
97 | break | |
98 | else: | |
99 | return line | |
100 | # We only get here if we see a section divider or EOM line | |
101 | if self.seekable: | |
102 | self.lastpos = self.tell() - len(line) | |
103 | self.level = i+1 | |
104 | if self.level > 1: | |
105 | raise Error,'Missing endmarker in MultiFile.readline()' | |
106 | return '' | |
107 | ||
108 | def readlines(self): | |
109 | list = [] | |
110 | while 1: | |
111 | line = self.readline() | |
112 | if not line: break | |
113 | list.append(line) | |
114 | return list | |
115 | ||
116 | def read(self): # Note: no size argument -- read until EOF only! | |
117 | return ''.join(self.readlines()) | |
118 | ||
119 | def next(self): | |
120 | while self.readline(): pass | |
121 | if self.level > 1 or self.last: | |
122 | return 0 | |
123 | self.level = 0 | |
124 | self.last = 0 | |
125 | if self.seekable: | |
126 | self.start = self.fp.tell() | |
127 | return 1 | |
128 | ||
129 | def push(self, sep): | |
130 | if self.level > 0: | |
131 | raise Error, 'bad MultiFile.push() call' | |
132 | self.stack.append(sep) | |
133 | if self.seekable: | |
134 | self.posstack.append(self.start) | |
135 | self.start = self.fp.tell() | |
136 | ||
137 | def pop(self): | |
138 | if self.stack == []: | |
139 | raise Error, 'bad MultiFile.pop() call' | |
140 | if self.level <= 1: | |
141 | self.last = 0 | |
142 | else: | |
143 | abslastpos = self.lastpos + self.start | |
144 | self.level = max(0, self.level - 1) | |
145 | self.stack.pop() | |
146 | if self.seekable: | |
147 | self.start = self.posstack.pop() | |
148 | if self.level > 0: | |
149 | self.lastpos = abslastpos - self.start | |
150 | ||
151 | def is_data(self, line): | |
152 | return line[:2] != '--' | |
153 | ||
154 | def section_divider(self, str): | |
155 | return "--" + str | |
156 | ||
157 | def end_marker(self, str): | |
158 | return "--" + str + "--" |