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c:\python24\lib \ email \ Encoders.py



0001 # Copyright (C) 2001-2004 Python Software Foundation
0002 # Author: Barry Warsaw
0003 # Contact: email-sig@python.org
0004 
0005 """Encodings and related functions."""
0006 
0007 import base64
0008 from quopri import encodestring as _encodestring
0009 
0010 def _qencode(s):
0011     enc = _encodestring(s, quotetabs=True)
0012     # Must encode spaces, which quopri.encodestring() doesn't do
0013     return enc.replace(' ', '=20')
0014 
0015 
0016 def _bencode(s):
0017     # We can't quite use base64.encodestring() since it tacks on a "courtesy
0018     # newline".  Blech!
0019     if not s:
0020         return s
0021     hasnewline = (s[-1] == '\n')
0022     value = base64.encodestring(s)
0023     if not hasnewline and value[-1] == '\n':
0024         return value[:-1]
0025     return value
0026 
0027 
0028 
0029 def encode_base64(msg):
0030     """Encode the message's payload in Base64.
0031 
0032     Also, add an appropriate Content-Transfer-Encoding header.
0033     """
0034     orig = msg.get_payload()
0035     encdata = _bencode(orig)
0036     msg.set_payload(encdata)
0037     msg['Content-Transfer-Encoding'] = 'base64'
0038 
0039 
0040 
0041 def encode_quopri(msg):
0042     """Encode the message's payload in quoted-printable.
0043 
0044     Also, add an appropriate Content-Transfer-Encoding header.
0045     """
0046     orig = msg.get_payload()
0047     encdata = _qencode(orig)
0048     msg.set_payload(encdata)
0049     msg['Content-Transfer-Encoding'] = 'quoted-printable'
0050 
0051 
0052 
0053 def encode_7or8bit(msg):
0054     """Set the Content-Transfer-Encoding header to 7bit or 8bit."""
0055     orig = msg.get_payload()
0056     if orig is None:
0057         # There's no payload.  For backwards compatibility we use 7bit
0058         msg['Content-Transfer-Encoding'] = '7bit'
0059         return
0060     # We play a trick to make this go fast.  If encoding to ASCII succeeds, we
0061     # know the data must be 7bit, otherwise treat it as 8bit.
0062     try:
0063         orig.encode('ascii')
0064     except UnicodeError:
0065         # iso-2022-* is non-ASCII but still 7-bit
0066         charset = msg.get_charset()
0067         output_cset = charset and charset.output_charset
0068         if output_cset and output_cset.lower().startswith('iso-2202-'):
0069             msg['Content-Transfer-Encoding'] = '7bit'
0070         else:
0071             msg['Content-Transfer-Encoding'] = '8bit'
0072     else:
0073         msg['Content-Transfer-Encoding'] = '7bit'
0074 
0075 
0076 
0077 def encode_noop(msg):
0078     """Do nothing."""
0079 

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