# -*- coding: utf-8 -*-
"""
LaTeX Lexer
~~~~~~~~~~~
This module contains all classes for lexing LaTeX code, as well as
general purpose base classes for incremental LaTeX decoders and
encoders, which could be useful in case you are writing your own
custom LaTeX codec.
.. autoclass:: Token(name, text)
:members: decode, __len__, __nonzero__
.. autoclass:: LatexLexer
:show-inheritance:
:members:
.. autoclass:: LatexIncrementalLexer
:show-inheritance:
:members:
.. autoclass:: LatexIncrementalDecoder
:show-inheritance:
:members:
.. autoclass:: LatexIncrementalEncoder
:show-inheritance:
:members:
"""
# Copyright (c) 2003, 2008 David Eppstein
# Copyright (c) 2011-2013 Matthias C. M. Troffaes
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.
import codecs
import collections
import re
[docs]class Token(collections.namedtuple("Token", "name text")):
"""A :func:`collections.namedtuple` storing information about a
matched token.
.. seealso:: :attr:`LatexLexer.tokens`
.. attribute:: name
The name of the token as a :class:`str`.
.. attribute:: text
The matched token text as :class:`bytes`.
The constructor also accepts text as :class:`memoryview`,
in which case it is automatically converted to :class:`bytes`.
This ensures that the token is hashable.
"""
__slots__ = () # efficiency
def __new__(cls, name=None, text=None):
# text can be memoryview; convert to bytes so Token remains hashable
return tuple.__new__(
cls,
(name if name is not None else 'unknown',
bytes(text) if text is not None else b''))
[docs] def __nonzero__(self):
"""Whether the token contains any text."""
return bool(self.text)
[docs] def __len__(self):
"""Length of the token text."""
return len(self.text)
[docs] def decode(self, encoding):
"""Returns the decoded token text in the specified *encoding*.
.. note::
Control words get an extra space added at the back to make
sure separation from the next token, so that decoded token
sequences can be :meth:`str.join`\ ed together.
For example, the tokens ``b'\\hello'`` and ``b'world'``
will correctly result in ``u'\\hello world'`` (remember
that LaTeX eats space following control words). If no space
were added, this would wrongfully result in
``u'\\helloworld'``.
"""
if self.name == 'control_word':
return self.text.decode(encoding) + u' '
else:
return self.text.decode(encoding)
# implementation note: we derive from IncrementalDecoder because this
# class serves excellently as a base class for incremental decoders,
# but of course we don't decode yet until later
[docs]class LatexLexer(codecs.IncrementalDecoder):
"""A very simple lexer for tex/latex code."""
# implementation note: every token **must** be decodable by inputenc
tokens = [
# comment: for ease, and for speed, we handle it as a token
('comment', br'%.*?\n'),
# control tokens
# in latex, some control tokens skip following whitespace
# ('control-word' and 'control-symbol')
# others do not ('control-symbol-x')
# XXX TBT says no control symbols skip whitespace (except '\ ')
# XXX but tests reveal otherwise?
('control_word', br'[\\][a-zA-Z]+'),
('control_symbol', br'[\\][~' br"'" br'"` =^!]'),
# TODO should only match ascii
('control_symbol_x', br'[\\][^a-zA-Z]'),
# parameter tokens
# also support a lone hash so we can lex things like b'#a'
('parameter', br'\#[0-9]|\#'),
# any remaining characters; for ease we also handle space and
# newline as tokens
('space', br' '),
('newline', br'\n'),
('mathshift', br'[$]'),
# note: some chars joined together to make it easier to detect
# symbols that have a special function (i.e. --, ---, etc.)
('chars',
br'---|--|-|[`][`]'
br"|['][']"
br'|[?][`]|[!][`]'
# separate chars because brackets are optional
# e.g. fran\\c cais = fran\\c{c}ais in latex
# so only way to detect \\c acting on c only is this way
br'|[0-9a-zA-Z{}]'
# we have to join everything else together to support
# multibyte encodings: every token must be decodable!!
# this means for instance that \\c öké is NOT equivalent to
# \\c{ö}ké
br'|[^ %#$\n\\]+'),
# trailing garbage which we cannot decode otherwise
# (such as a lone '\' at the end of a buffer)
# is never emitted, but used internally by the buffer
('unknown', br'.'),
]
"""List of token names, and the regular expressions they match."""
def __init__(self, errors='strict'):
"""Initialize the codec."""
self.errors = errors
# regular expression used for matching
self.regexp = re.compile(
b"|".join(
b"(?P<" + name.encode() + b">" + regexp + b")"
for name, regexp in self.tokens),
re.DOTALL)
# reset state
self.reset()
[docs] def reset(self):
"""Reset state."""
# buffer for storing last (possibly incomplete) token
self.raw_buffer = Token()
[docs] def getstate(self):
"""Get state."""
return (self.raw_buffer.text, 0)
[docs] def setstate(self, state):
"""Set state. The *state* must correspond to the return value
of a previous :meth:`getstate` call.
"""
self.raw_buffer = Token('unknown', state[0])
[docs] def get_raw_tokens(self, bytes_, final=False):
"""Yield tokens without any further processing. Tokens are one of:
- ``\\<word>``: a control word (i.e. a command)
- ``\\<symbol>``: a control symbol (i.e. \\^ etc.)
- ``#<n>``: a parameter
- a series of byte characters
"""
if self.raw_buffer:
bytes_ = self.raw_buffer.text + bytes_
self.raw_buffer = Token()
for match in self.regexp.finditer(bytes_):
for name, regexp in self.tokens:
text = match.group(name)
if text is not None:
# yield the buffer token(s)
for token in self.flush_raw_tokens():
yield token
# fill buffer with next token
self.raw_buffer = Token(name, text)
break
if final:
for token in self.flush_raw_tokens():
yield token
[docs] def flush_raw_tokens(self):
"""Flush the raw token buffer."""
if self.raw_buffer:
yield self.raw_buffer
self.raw_buffer = Token()
[docs]class LatexIncrementalLexer(LatexLexer):
"""A very simple incremental lexer for tex/latex code. Roughly
follows the state machine described in Tex By Topic, Chapter 2.
The generated tokens satisfy:
* no newline characters: paragraphs are separated by '\\par'
* spaces following control tokens are compressed
"""
def reset(self):
LatexLexer.reset(self)
# three possible states:
# newline (N), skipping spaces (S), and middle of line (M)
self.state = 'N'
# inline math mode?
self.inline_math = False
def getstate(self):
# state 'M' is most common, so let that be zero
return (
self.raw_buffer,
{'M': 0, 'N': 1, 'S': 2}[self.state]
| (4 if self.inline_math else 0)
)
def setstate(self, state):
self.raw_buffer = state[0]
self.state = {0: 'M', 1: 'N', 2: 'S'}[state[1] & 3]
self.inline_math = bool(state[1] & 4)
[docs] def get_tokens(self, bytes_, final=False):
"""Yield tokens while maintaining a state. Also skip
whitespace after control words and (some) control symbols.
Replaces newlines by spaces and \\par commands depending on
the context.
"""
# current position relative to the start of bytes_ in the sequence
# of bytes that have been decoded
pos = -len(self.raw_buffer)
for token in self.get_raw_tokens(bytes_, final=final):
pos = pos + len(token)
assert pos >= 0 # first token includes at least self.raw_buffer
if token.name == 'newline':
if self.state == 'N':
# if state was 'N', generate new paragraph
yield Token('control_word', b'\\par')
elif self.state == 'S':
# switch to 'N' state, do not generate a space
self.state = 'N'
elif self.state == 'M':
# switch to 'N' state, generate a space
self.state = 'N'
yield Token('space', b' ')
else:
raise AssertionError(
"unknown tex state '%s'" % self.state)
elif token.name == 'space':
if self.state == 'N':
# remain in 'N' state, no space token generated
pass
elif self.state == 'S':
# remain in 'S' state, no space token generated
pass
elif self.state == 'M':
# in M mode, generate the space,
# but switch to space skip mode
self.state = 'S'
yield token
else:
raise AssertionError(
"unknown state %s" % repr(self.state))
elif token.name == 'mathshift':
self.inline_math = not self.inline_math
yield token
elif token.name == 'parameter':
self.state = 'M'
yield token
elif token.name == 'control_word':
# go to space skip mode
self.state = 'S'
yield token
elif token.name == 'control_symbol':
# go to space skip mode
self.state = 'S'
yield token
elif token.name == 'control_symbol_x':
# don't skip following space, so go to M mode
self.state = 'M'
yield token
elif token.name == 'comment':
# go to newline mode, no token is generated
# note: comment includes the newline
self.state = 'N'
elif token.name == 'chars':
self.state = 'M'
yield token
elif token.name == 'unknown':
if self.errors == 'strict':
# current position within bytes_
# this is the position right after the unknown token
raise UnicodeDecodeError(
"latex", # codec
bytes_, # problematic input
pos - len(token), # start of problematic token
pos, # end of it
"unknown token %s" % repr(token.text))
elif self.errors == 'ignore':
# do nothing
pass
elif self.errors == 'replace':
yield Token('chars', b'?' * len(token))
else:
raise NotImplementedError(
"error mode %s not supported" % repr(self.errors))
else:
raise AssertionError(
"unknown token name %s" % repr(token.name))
[docs]class LatexIncrementalDecoder(LatexIncrementalLexer):
"""Simple incremental decoder. Transforms lexed LaTeX tokens into
unicode.
To customize decoding, subclass and override
:meth:`get_unicode_tokens`.
"""
inputenc = "ascii"
"""Input encoding. **Must** extend ascii."""
[docs] def get_unicode_tokens(self, bytes_, final=False):
"""Decode every token in :attr:`inputenc` encoding. Override to
process the tokens in some other way (for example, for token
translation).
"""
for token in self.get_tokens(bytes_, final=final):
yield token.decode(self.inputenc)
[docs] def decode(self, bytes_, final=False):
"""Decode LaTeX *bytes_* into a unicode string.
This implementation calls :meth:`get_unicode_tokens` and joins
the resulting unicode strings together.
"""
try:
return u''.join(self.get_unicode_tokens(bytes_, final=final))
except UnicodeDecodeError as e:
# API requires that the encode method raises a ValueError
# in this case
raise ValueError(e)
[docs]class LatexIncrementalEncoder(codecs.IncrementalEncoder):
"""Simple incremental encoder for LaTeX. Transforms unicode into
:class:`bytes`.
To customize decoding, subclass and override
:meth:`get_latex_bytes`.
"""
inputenc = "ascii"
"""Input encoding. **Must** extend ascii."""
[docs] def get_latex_bytes(self, unicode_, final=False):
"""Encode every character in :attr:`inputenc` encoding. Override to
process the unicode in some other way (for example, for character
translation).
"""
if not isinstance(unicode_, basestring):
raise TypeError(
"expected unicode for encode input, but got {0} instead"
.format(unicode_.__class__.__name__))
for c in unicode_:
yield c.encode(self.inputenc, self.errors)
[docs] def encode(self, unicode_, final=False):
"""Encode the *unicode_* string into LaTeX :class:`bytes`.
This implementation calls :meth:`get_latex_bytes` and joins
the resulting :class:`bytes` together.
"""
try:
return b''.join(self.get_latex_bytes(unicode_, final=final))
except UnicodeEncodeError as e:
# API requires that the encode method raises a ValueError
# in this case
raise ValueError(e)