Python2.src.antlr4.CommonTokenStream.py Maven / Gradle / Ivy

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A collection of tests for ANTLR 4 Runtime libraries.
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#
# [The "BSD license"]
#  Copyright (c) 2012 Terence Parr
#  Copyright (c) 2012 Sam Harwell
#  Copyright (c) 2014 Eric Vergnaud
#  All rights reserved.
#
#  Redistribution and use in source and binary forms, with or without
#  modification, are permitted provided that the following conditions
#  are met:
#
#  1. Redistributions of source code must retain the above copyright
#     notice, this list of conditions and the following disclaimer.
#  2. Redistributions in binary form must reproduce the above copyright
#     notice, this list of conditions and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#  3. The name of the author may not be used to endorse or promote products
#     derived from this software without specific prior written permission.
#
#  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
#  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
#  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
#  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
#  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
#  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
#  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
#  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
#  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
#  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#/

#
# This class extends {@link BufferedTokenStream} with functionality to filter
# token streams to tokens on a particular channel (tokens where
# {@link Token#getChannel} returns a particular value).
#
# 
# This token stream provides access to all tokens by index or when calling
# methods like {@link #getText}. The channel filtering is only used for code
# accessing tokens via the lookahead methods {@link #LA}, {@link #LT}, and
# {@link #LB}.
#
# 
# By default, tokens are placed on the default channel
# ({@link Token#DEFAULT_CHANNEL}), but may be reassigned by using the
# {@code ->channel(HIDDEN)} lexer command, or by using an embedded action to
# call {@link Lexer#setChannel}.
# 
#
# 
# Note: lexer rules which use the {@code ->skip} lexer command or call
# {@link Lexer#skip} do not produce tokens at all, so input text matched by
# such a rule will not be available as part of the token stream, regardless of
# channel.
#/

from antlr4.BufferedTokenStream import BufferedTokenStream
from antlr4.Token import Token


class CommonTokenStream(BufferedTokenStream):

    def __init__(self, lexer, channel=Token.DEFAULT_CHANNEL):
        super(CommonTokenStream, self).__init__(lexer)
        self.channel = channel

    def adjustSeekIndex(self, i):
        return self.nextTokenOnChannel(i, self.channel)

    def LB(self, k):
        if k==0 or (self.index-k)<0:
            return None
        i = self.index
        n = 1
        # find k good tokens looking backwards
        while n <= k:
            # skip off-channel tokens
            i = self.previousTokenOnChannel(i - 1, self.channel)
            n += 1
        if i < 0:
            return None
        return self.tokens[i]

    def LT(self, k):
        self.lazyInit()
        if k == 0:
            return None
        if k < 0:
            return self.LB(-k)
        i = self.index
        n = 1 # we know tokens[pos] is a good one
        # find k good tokens
        while n < k:
            # skip off-channel tokens, but make sure to not look past EOF
            if self.sync(i + 1):
                i = self.nextTokenOnChannel(i + 1, self.channel)
            n += 1
        return self.tokens[i]

    # Count EOF just once.#/
    def getNumberOfOnChannelTokens(self):
        n = 0
        self.fill()
        for i in range(0, len(self.tokens)):
            t = self.tokens[i]
            if t.channel==self.channel:
                n += 1
            if t.type==Token.EOF:
                break
        return n