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# A class that 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.
# Note that if a nested multipart message is terminated by a separator
# for an outer message, this is not reported, even though it is really
# illegal input.
import sys
import string
err = sys.stderr.write
Error = 'multifile.Error'
class MultiFile:
#
def __init__(self, fp):
self.fp = fp
self.stack = [] # Grows down
self.level = 0
self.last = 0
self.start = self.fp.tell()
self.posstack = [] # Grows down
#
def tell(self):
if self.level > 0:
return self.lastpos
return self.fp.tell() - self.start
#
def seek(self, pos):
if not 0 <= pos <= self.tell() 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
#
def readline(self):
if self.level > 0: return ''
line = self.fp.readline()
if not line:
self.level = len(self.stack)
self.last = (self.level > 0)
if self.last:
err('*** Sudden EOF in MultiFile.readline()\n')
return ''
if line[:2] <> '--': return line
n = len(line)
k = n
while k > 0 and line[k-1] in string.whitespace: k = k-1
mark = line[2:k]
if mark[-2:] == '--': mark1 = mark[:-2]
else: mark1 = None
for i in range(len(self.stack)):
sep = self.stack[i]
if sep == mark:
self.last = 0
break
elif mark1 <> None and sep == mark1:
self.last = 1
break
else:
return line
# Get here after break out of loop
self.lastpos = self.tell() - len(line)
self.level = i+1
if self.level > 1:
err('*** Missing endmarker in MultiFile.readline()\n')
return ''
#
def next(self):
while self.readline(): pass
if self.level > 1 or self.last:
return 0
self.level = 0
self.last = 0
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)
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]
self.start = self.posstack[0]
del self.posstack[0]
if self.level > 0:
self.lastpos = abslastpos - self.start
#
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