cpython/Lib/rfc822.py

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# RFC-822 message manipulation class.
#
# XXX This is only a very rough sketch of a full RFC-822 parser;
# additional methods are needed to parse addresses and dates, and to
# tokenize lines according to various other syntax rules.
#
# Directions for use:
#
# To create a Message object: first open a file, e.g.:
# fp = open(file, 'r')
# (or use any other legal way of getting an open file object, e.g. use
# sys.stdin or call os.popen()).
# Then pass the open file object to the init() method of Message:
# m = Message().init(fp)
#
# To get the text of a particular header there are several methods:
# str = m.getheader(name)
# str = m.getrawheader(name)
# where name is the name of the header, e.g. 'Subject'.
# The difference is that getheader() strips the leading and trailing
# whitespace, while getrawheader() doesn't. Both functions retain
# embedded whitespace (including newlines) exactly as they are
# specified in the header, and leave the case of the text unchanged.
#
# See the class definition for lower level access methods.
#
# There are also some utility functions here.
import regex
import string
class Message:
# Initialize the class instance and read the headers.
def init(self, fp):
self.fp = fp
#
try:
self.startofheaders = self.fp.tell()
except IOError:
self.startofheaders = None
#
self.readheaders()
#
try:
self.startofbody = self.fp.tell()
except IOError:
self.startofbody = None
#
return self
# Rewind the file to the start of the body (if seekable).
def rewindbody(self):
self.fp.seek(self.startofbody)
# Read header lines up to the entirely blank line that
# terminates them. The (normally blank) line that ends the
# headers is skipped, but not included in the returned list.
# If a non-header line ends the headers, (which is an error),
# an attempt is made to backspace over it; it is never
# included in the returned list.
#
# The variable self.status is set to the empty string if all
# went well, otherwise it is an error message.
# The variable self.headers is a completely uninterpreted list
# of lines contained in the header (so printing them will
# reproduce the header exactly as it appears in the file).
def readheaders(self):
self.headers = list = []
self.status = ''
headerseen = 0
while 1:
line = self.fp.readline()
if not line:
self.status = 'EOF in headers'
break
if self.islast(line):
break
elif headerseen and line[0] in ' \t':
# It's a continuation line.
list.append(line)
elif regex.match('^[!-9;-~]+:', line):
# It's a header line.
list.append(line)
headerseen = 1
else:
# It's not a header line; stop here.
if not headerseen:
self.status = 'No headers'
else:
self.status = 'Bad header'
# Try to undo the read.
try:
self.fp.seek(-len(line), 1)
except IOError:
self.status = \
self.status + '; bad seek'
break
# Method to determine whether a line is a legal end of
# RFC-822 headers. You may override this method if your
# application wants to bend the rules, e.g. to accept lines
# ending in '\r\n', to strip trailing whitespace, or to
# recognise MH template separators ('--------').
def islast(self, line):
return line == '\n'
# Look through the list of headers and find all lines matching
# a given header name (and their continuation lines).
# A list of the lines is returned, without interpretation.
# If the header does not occur, an empty list is returned.
# If the header occurs multiple times, all occurrences are
# returned. Case is not important in the header name.
def getallmatchingheaders(self, name):
name = string.lower(name) + ':'
n = len(name)
list = []
hit = 0
for line in self.headers:
if string.lower(line[:n]) == name:
hit = 1
elif line[:1] not in string.whitespace:
hit = 0
if hit:
list.append(line)
return list
# Similar, but return only the first matching header (and its
# continuation lines).
def getfirstmatchingheader(self, name):
name = string.lower(name) + ':'
n = len(name)
list = []
hit = 0
for line in self.headers:
if string.lower(line[:n]) == name:
hit = 1
elif line[:1] not in string.whitespace:
if hit:
break
if hit:
list.append(line)
return list
# A higher-level interface to getfirstmatchingheader().
# Return a string containing the literal text of the header
# but with the keyword stripped. All leading, trailing and
# embedded whitespace is kept in the string, however.
# Return None if the header does not occur.
def getrawheader(self, name):
list = self.getfirstmatchingheader(name)
if not list:
return None
list[0] = list[0][len(name) + 1:]
return string.joinfields(list, '')
# Going one step further: also strip leading and trailing
# whitespace.
def getheader(self, name):
text = self.getrawheader(name)
if text == None:
return None
return string.strip(text)
# XXX The next step would be to define self.getaddr(name)
# and self.getaddrlist(name) which would parse a header
# consisting of a single mail address and a number of mail
# addresses, respectively. Lower level functions would be
# parseaddr(string) and parseaddrlist(string).
# XXX Similar, there would be a function self.getdate(name) to
# return a date in canonical form (perhaps a number compatible
# to time.time()) and a function parsedate(string).
# XXX The inverses of the parse functions may also be useful.
# Utility functions
# -----------------
# Remove quotes from a string.
# XXX Should fix this to be really conformant.
def unquote(str):
if len(str) > 1:
if str[0] == '"' and str[-1:] == '"':
return str[1:-1]
if str[0] == '<' and str[-1:] == '>':
return str[1:-1]
return str