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| # | |
| # Copyright (c) 2012-2017 The ANTLR Project. All rights reserved. | |
| # Use of this file is governed by the BSD 3-clause license that | |
| # can be found in the LICENSE.txt file in the project root. | |
| #/ | |
| # | |
| # 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). | |
| # | |
| # <p> | |
| # 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}.</p> | |
| # | |
| # <p> | |
| # 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}. | |
| # </p> | |
| # | |
| # <p> | |
| # 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.</p> | |
| #/ | |
| from antlr4.BufferedTokenStream import BufferedTokenStream | |
| from antlr4.Lexer import Lexer | |
| from antlr4.Token import Token | |
| class CommonTokenStream(BufferedTokenStream): | |
| __slots__ = 'channel' | |
| def __init__(self, lexer:Lexer, channel:int=Token.DEFAULT_CHANNEL): | |
| super().__init__(lexer) | |
| self.channel = channel | |
| def adjustSeekIndex(self, i:int): | |
| return self.nextTokenOnChannel(i, self.channel) | |
| def LB(self, k:int): | |
| 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:int): | |
| 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 | |