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# Copyright (c) 2014, Menno Smits
# Released subject to the New BSD License
# Please see http://en.wikipedia.org/wiki/BSD_licenses
"""
A lexical analyzer class for IMAP responses.
Although Lexer does all the work, TokenSource is the class to use for
external callers.
"""
from typing import Iterator, List, Optional, Tuple, TYPE_CHECKING, Union
from .util import assert_imap_protocol
__all__ = ["TokenSource"]
CTRL_CHARS = frozenset(c for c in range(32))
ALL_CHARS = frozenset(c for c in range(256))
SPECIALS = frozenset(c for c in b' ()%"[')
NON_SPECIALS = ALL_CHARS - SPECIALS - CTRL_CHARS
WHITESPACE = frozenset(c for c in b" \t\r\n")
BACKSLASH = ord("\\")
OPEN_SQUARE = ord("[")
CLOSE_SQUARE = ord("]")
DOUBLE_QUOTE = ord('"')
class TokenSource:
"""
A simple iterator for the Lexer class that also provides access to
the current IMAP literal.
"""
def __init__(self, text: List[bytes]):
self.lex = Lexer(text)
self.src = iter(self.lex)
@property
def current_literal(self) -> Optional[bytes]:
if TYPE_CHECKING:
assert self.lex.current_source is not None
return self.lex.current_source.literal
def __iter__(self) -> Iterator[bytes]:
return self.src
class Lexer:
"""
A lexical analyzer class for IMAP
"""
def __init__(self, text: List[bytes]):
self.sources = (LiteralHandlingIter(chunk) for chunk in text)
self.current_source: Optional[LiteralHandlingIter] = None
def read_until(
self, stream_i: "PushableIterator", end_char: int, escape: bool = True
) -> bytearray:
token = bytearray()
try:
for nextchar in stream_i:
if escape and nextchar == BACKSLASH:
escaper = nextchar
nextchar = next(stream_i)
if nextchar not in (escaper, end_char):
token.append(escaper) # Don't touch invalid escaping
elif nextchar == end_char:
break
token.append(nextchar)
else:
raise ValueError("No closing '%s'" % chr(end_char))
except StopIteration:
raise ValueError("No closing '%s'" % chr(end_char))
token.append(end_char)
return token
def read_token_stream(self, stream_i: "PushableIterator") -> Iterator[bytearray]:
whitespace = WHITESPACE
wordchars = NON_SPECIALS
read_until = self.read_until
while True:
# Whitespace
for nextchar in stream_i:
if nextchar not in whitespace:
stream_i.push(nextchar)
break # done skipping over the whitespace
# Non-whitespace
token = bytearray()
for nextchar in stream_i:
if nextchar in wordchars:
token.append(nextchar)
elif nextchar == OPEN_SQUARE:
token.append(nextchar)
token.extend(read_until(stream_i, CLOSE_SQUARE, escape=False))
else:
if nextchar in whitespace:
yield token
elif nextchar == DOUBLE_QUOTE:
assert_imap_protocol(not token)
token.append(nextchar)
token.extend(read_until(stream_i, nextchar))
yield token
else:
# Other punctuation, eg. "(". This ends the current token.
if token:
yield token
yield bytearray([nextchar])
break
else:
if token:
yield token
break
def __iter__(self) -> Iterator[bytes]:
for source in self.sources:
self.current_source = source
for tok in self.read_token_stream(iter(source)):
yield bytes(tok)
# imaplib has poor handling of 'literals' - it both fails to remove the
# {size} marker, and fails to keep responses grouped into the same logical
# 'line'. What we end up with is a list of response 'records', where each
# record is either a simple string, or tuple of (str_with_lit, literal) -
# where str_with_lit is a string with the {xxx} marker at its end. Note
# that each element of this list does *not* correspond 1:1 with the
# untagged responses.
# (http://bugs.python.org/issue5045 also has comments about this)
# So: we have a special object for each of these records. When a
# string literal is processed, we peek into this object to grab the
# literal.
class LiteralHandlingIter:
def __init__(self, resp_record: Union[Tuple[bytes, bytes], bytes]):
self.literal: Optional[bytes]
if isinstance(resp_record, tuple):
# A 'record' with a string which includes a literal marker, and
# the literal itself.
self.src_text = resp_record[0]
assert_imap_protocol(self.src_text.endswith(b"}"), self.src_text)
self.literal = resp_record[1]
else:
# just a line with no literals.
self.src_text = resp_record
self.literal = None
def __iter__(self) -> "PushableIterator":
return PushableIterator(self.src_text)
class PushableIterator:
NO_MORE = object()
def __init__(self, it: bytes):
self.it = iter(it)
self.pushed: List[int] = []
def __iter__(self) -> "PushableIterator":
return self
def __next__(self) -> int:
if self.pushed:
return self.pushed.pop()
return next(self.it)
# For Python 2 compatibility
next = __next__
def push(self, item: int) -> None:
self.pushed.append(item)
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