Lib/dos-8x3/multifil.py

   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 import sys
  31 import string
  32
  33 class Error(Exception):
  34         pass
  35
  36 class MultiFile:
  37
  38         seekable = 0
  39
  40         def __init__(self, fp, seekable=1):
  41                 self.fp = fp
  42                 self.stack = [] # Grows down
  43                 self.level = 0
  44                 self.last = 0
  45                 if seekable:
  46                         self.seekable = 1
  47                         self.start = self.fp.tell()
  48                         self.posstack = [] # Grows down
  49
  50         def tell(self):
  51                 if self.level > 0:
  52                         return self.lastpos
  53                 return self.fp.tell() - self.start
  54
  55         def seek(self, pos, whence=0):
  56                 here = self.tell()
  57                 if whence:
  58                         if whence == 1:
  59                                 pos = pos + here
  60                         elif whence == 2:
  61                                 if self.level > 0:
  62                                         pos = pos + self.lastpos
  63                                 else:
  64                                         raise Error, "can't use whence=2 yet"
  65                 if not 0 <= pos <= here or \
  66                                 self.level > 0 and pos > self.lastpos:
  67                         raise Error, 'bad MultiFile.seek() call'
  68                 self.fp.seek(pos + self.start)
  69                 self.level = 0
  70                 self.last = 0
  71
  72         def readline(self):
  73                 if self.level > 0:
  74                         return ''
  75                 line = self.fp.readline()
  76                 # Real EOF?
  77                 if not line:
  78                         self.level = len(self.stack)
  79                         self.last = (self.level > 0)
  80                         if self.last:
  81                                 raise Error, 'sudden EOF in MultiFile.readline()'
  82                         return ''
  83                 assert self.level == 0
  84                 # Fast check to see if this is just data
  85                 if self.is_data(line):
  86                         return line
  87                 else:
  88                         # Ignore trailing whitespace on marker lines
  89                         k = len(line) - 1;
  90                         while line[k] in string.whitespace:
  91                                 k = k - 1
  92                         marker = line[:k+1]
  93                 # No?  OK, try to match a boundary.
  94                 # Return the line (unstripped) if we don't.
  95                 for i in range(len(self.stack)):
  96                         sep = self.stack[i]
  97                         if marker == self.section_divider(sep):
  98                                 self.last = 0
  99                                 break
 100                         elif marker == self.end_marker(sep):
 101                                 self.last = 1
 102                                 break
 103                 else:
 104                         return line
 105                 # We only get here if we see a section divider or EOM line
 106                 if self.seekable:
 107                         self.lastpos = self.tell() - len(line)
 108                 self.level = i+1
 109                 if self.level > 1:
 110                         raise Error,'Missing endmarker in MultiFile.readline()'
 111                 return ''
 112
 113         def readlines(self):
 114                 list = []
 115                 while 1:
 116                         line = self.readline()
 117                         if not line: break
 118                         list.append(line)
 119                 return list
 120
 121         def read(self): # Note: no size argument -- read until EOF only!
 122                 return string.joinfields(self.readlines(), '')
 123
 124         def next(self):
 125                 while self.readline(): pass
 126                 if self.level > 1 or self.last:
 127                         return 0
 128                 self.level = 0
 129                 self.last = 0
 130                 if self.seekable:
 131                         self.start = self.fp.tell()
 132                 return 1
 133
 134         def push(self, sep):
 135                 if self.level > 0:
 136                         raise Error, 'bad MultiFile.push() call'
 137                 self.stack.insert(0, sep)
 138                 if self.seekable:
 139                         self.posstack.insert(0, self.start)
 140                         self.start = self.fp.tell()
 141
 142         def pop(self):
 143                 if self.stack == []:
 144                         raise Error, 'bad MultiFile.pop() call'
 145                 if self.level <= 1:
 146                         self.last = 0
 147                 else:
 148                         abslastpos = self.lastpos + self.start
 149                 self.level = max(0, self.level - 1)
 150                 del self.stack[0]
 151                 if self.seekable:
 152                         self.start = self.posstack[0]
 153                         del self.posstack[0]
 154                         if self.level > 0:
 155                                 self.lastpos = abslastpos - self.start
 156
 157         def is_data(self, line):
 158                 return line[:2] <> '--'
 159
 160         def section_divider(self, str):
 161                 return "--" + str
 162
 163         def end_marker(self, str):
 164                 return "--" + str + "--"