def decode_header(header):
"""Decode a message header value without converting charset.
Returns a list of (string, charset) pairs containing each of the decoded
parts of the header. Charset is None for non-encoded parts of the header,
otherwise a lower-case string containing the name of the character set
specified in the encoded string.
header may be a string that may or may not contain RFC2047 encoded words,
or it may be a Header object.
An email.errors.HeaderParseError may be raised when certain decoding error
occurs (e.g. a base64 decoding exception).
"""
# If it is a Header object, we can just return the encoded chunks.
if hasattr(header, "_chunks"):
return [(_charset._encode(string, str(charset)), str(charset))
for string, charset in header._chunks]
# If no encoding, just return the header with no charset.
if not ecre.search(header):
return [(header, None)]
# First step is to parse all the encoded parts into triplets of the form
# (encoded_string, encoding, charset). For unencoded strings, the last
# two parts will be None.
words = []
for line in header.splitlines():
parts = ecre.split(line)
first = True
while parts:
unencoded = parts.pop(0)
if first:
unencoded = unencoded.lstrip()
first = False
if unencoded:
words.append((unencoded, None, None))
if parts:
charset = parts.pop(0).lower()
encoding = parts.pop(0).lower()
encoded = parts.pop(0)
words.append((encoded, encoding, charset))
# Now loop over words and remove words that consist of whitespace
# between two encoded strings.
import sys
droplist = []
for n, w in enumerate(words):
if n > 1 and w[1] and words[n - 2][1] and words[n - 1][0].isspace():
droplist.append(n - 1)
for d in reversed(droplist):
del words[d]
# The next step is to decode each encoded word by applying the reverse
# base64 or quopri transformation. decoded_words is now a list of the
# form (decoded_word, charset).
decoded_words = []
for encoded_string, encoding, charset in words:
if encoding is None:
# This is an unencoded word.
decoded_words.append((encoded_string, charset))
elif encoding == "q":
word = header_decode(encoded_string)
decoded_words.append((word, charset))
elif encoding == "b":
paderr = len(
encoded_string) % 4 # Postel's law: add missing padding
if paderr:
encoded_string += "==="[:4 - paderr]
try:
word = base64mime.decode(encoded_string)
except binascii.Error:
raise HeaderParseError("Base64 decoding error")
else:
decoded_words.append((word, charset))
else:
raise AssertionError("Unexpected encoding: " + encoding)
# Now convert all words to bytes and collapse consecutive runs of
# similarly encoded words.
collapsed = []
last_word = last_charset = None
for word, charset in decoded_words:
if isinstance(word, str):
word = bytes(word, "raw-unicode-escape")
if last_word is None:
last_word = word
last_charset = charset
elif charset != last_charset:
collapsed.append((last_word, last_charset))
last_word = word
last_charset = charset
elif last_charset is None:
last_word += BSPACE + word
else:
last_word += word
collapsed.append((last_word, last_charset))
return collapsed
def decode_header(header):
"""Decode a message header value without converting charset.
Returns a list of (string, charset) pairs containing each of the decoded
parts of the header. Charset is None for non-encoded parts of the header,
otherwise a lower-case string containing the name of the character set
specified in the encoded string.
header may be a string that may or may not contain RFC2047 encoded words,
or it may be a Header object.
An email.errors.HeaderParseError may be raised when certain decoding error
occurs (e.g. a base64 decoding exception).
"""
# If it is a Header object, we can just return the encoded chunks.
if hasattr(header, '_chunks'):
return [(_charset._encode(string, str(charset)), str(charset))
for string, charset in header._chunks]
# If no encoding, just return the header with no charset.
if not ecre.search(header):
return [(header, None)]
# First step is to parse all the encoded parts into triplets of the form
# (encoded_string, encoding, charset). For unencoded strings, the last
# two parts will be None.
words = []
for line in header.splitlines():
parts = ecre.split(line)
first = True
while parts:
unencoded = parts.pop(0)
if first:
unencoded = unencoded.lstrip()
first = False
if unencoded:
words.append((unencoded, None, None))
if parts:
charset = parts.pop(0).lower()
encoding = parts.pop(0).lower()
encoded = parts.pop(0)
words.append((encoded, encoding, charset))
# Now loop over words and remove words that consist of whitespace
# between two encoded strings.
import sys
droplist = []
for n, w in enumerate(words):
if n>1 and w[1] and words[n-2][1] and words[n-1][0].isspace():
droplist.append(n-1)
for d in reversed(droplist):
del words[d]
# The next step is to decode each encoded word by applying the reverse
# base64 or quopri transformation. decoded_words is now a list of the
# form (decoded_word, charset).
decoded_words = []
for encoded_string, encoding, charset in words:
if encoding is None:
# This is an unencoded word.
decoded_words.append((encoded_string, charset))
elif encoding == 'q':
word = header_decode(encoded_string)
decoded_words.append((word, charset))
elif encoding == 'b':
paderr = len(encoded_string) % 4 # Postel's law: add missing padding
if paderr:
encoded_string += '==='[:4 - paderr]
try:
word = base64mime.decode(encoded_string)
except binascii.Error:
raise HeaderParseError('Base64 decoding error')
else:
decoded_words.append((word, charset))
else:
raise AssertionError('Unexpected encoding: ' + encoding)
# Now convert all words to bytes and collapse consecutive runs of
# similarly encoded words.
collapsed = []
last_word = last_charset = None
for word, charset in decoded_words:
if isinstance(word, str):
word = bytes(word, 'raw-unicode-escape')
if last_word is None:
last_word = word
last_charset = charset
elif charset != last_charset:
collapsed.append((last_word, last_charset))
last_word = word
last_charset = charset
elif last_charset is None:
last_word += BSPACE + word
else:
last_word += word
collapsed.append((last_word, last_charset))
return collapsed