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