| """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[0] |
| del self.posstack[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 + "--" |