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"""A readline()-style interface to the parts of a multipart message.
The MultiFile class makes each part of a multipart message "feel" like
an ordinary file, as long as you use fp.readline(). Allows recursive
use, for nested multipart messages. Probably best used together
with module mimetools.
Suggested use:
real_fp = open(...)
fp = MultiFile(real_fp)
"read some lines from fp"
fp.push(separator)
while 1:
"read lines from fp until it returns an empty string" (A)
if not fp.next(): break
fp.pop()
"read remaining lines from fp until it returns an empty string"
The latter sequence may be used recursively at (A).
It is also allowed to use multiple push()...pop() sequences.
If seekable is given as 0, the class code will not do the bookkeeping
it normally attempts in order to make seeks relative to the beginning of the
current file part. This may be useful when using MultiFile with a non-
seekable stream object.
"""
__all__ = ["MultiFile","Error"]
class Error(Exception):
pass
class MultiFile:
seekable = 0
def __init__(self, fp, seekable=1):
self.fp = fp
self.stack = [] # Grows down
self.level = 0
self.last = 0
self.readahead = ""
if seekable:
self.seekable = 1
self.start = self.fp.tell()
self.posstack = [] # Grows down
def tell(self):
if self.level > 0:
return self.lastpos
return self.fp.tell() - len(self.readahead) - self.start
def seek(self, pos, whence=0):
here = self.tell()
if whence:
if whence == 1:
pos = pos + here
elif whence == 2:
if self.level > 0:
pos = pos + self.lastpos
else:
raise Error, "can't use whence=2 yet"
if not 0 <= pos <= here or \
self.level > 0 and pos > self.lastpos:
raise Error, 'bad MultiFile.seek() call'
self.fp.seek(pos + self.start)
self.level = 0
self.last = 0
self.readahead = ""
def readline(self):
if not self.readahead:
self.readahead = self._readline()
line = self.readahead
if line:
self.readahead = self._readline()
if not self.readahead:
if line[-2:] == "\r\n":
line = line[:-2]
elif line[-1:] == "\n":
line = line[:-1]
return line
def _readline(self):
if self.level > 0:
return ''
line = self.fp.readline()
# Real EOF?
if not line:
self.level = len(self.stack)
self.last = (self.level > 0)
if self.last:
raise Error, 'sudden EOF in MultiFile.readline()'
return ''
assert self.level == 0
# Fast check to see if this is just data
if self.is_data(line):
return line
else:
# Ignore trailing whitespace on marker lines
marker = line.rstrip()
# No? OK, try to match a boundary.
# Return the line (unstripped) if we don't.
for i in range(len(self.stack)):
sep = self.stack[i]
if marker == self.section_divider(sep):
self.last = 0
break
elif marker == self.end_marker(sep):
self.last = 1
break
else:
return line
# We only get here if we see a section divider or EOM line
if self.seekable:
self.lastpos = self.tell() - len(line)
self.level = i+1
if self.level > 1:
raise Error,'Missing endmarker in MultiFile.readline()'
return ''
def readlines(self):
list = []
while 1:
line = self.readline()
if not line: break
list.append(line)
return list
def read(self): # Note: no size argument -- read until EOF only!
return ''.join(self.readlines())
def next(self):
while self.readline(): pass
if self.level > 1 or self.last:
return 0
self.level = 0
self.last = 0
if self.seekable:
self.start = self.fp.tell()
return 1
def push(self, sep):
if self.level > 0:
raise Error, 'bad MultiFile.push() call'
self.stack.insert(0, sep)
if self.seekable:
self.posstack.insert(0, self.start)
self.start = self.fp.tell()
def pop(self):
if self.stack == []:
raise Error, 'bad MultiFile.pop() call'
if self.level <= 1:
self.last = 0
else:
abslastpos = self.lastpos + self.start
self.level = max(0, self.level - 1)
del self.stack[0]
if self.seekable:
self.start = self.posstack.pop(0)
if self.level > 0:
self.lastpos = abslastpos - self.start
def is_data(self, line):
return line[:2] != '--'
def section_divider(self, str):
return "--" + str
def end_marker(self, str):
return "--" + str + "--"
|
