Lib/dos-8x3/multifil.py

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