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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 implementation of {@link TokenStream} loads tokens from a
# {@link TokenSource} on-demand, and places the tokens in a buffer to provide
# access to any previous token by index.
#
# <p>
# This token stream ignores the value of {@link Token#getChannel}. If your
# parser requires the token stream filter tokens to only those on a particular
# channel, such as {@link Token#DEFAULT_CHANNEL} or
# {@link Token#HIDDEN_CHANNEL}, use a filtering token stream such a
# {@link CommonTokenStream}.</p>
from io import StringIO
from antlr4.Token import Token
from antlr4.error.Errors import IllegalStateException
# need forward declaration
Lexer = None
# this is just to keep meaningful parameter types to Parser
class TokenStream(object):
pass
class BufferedTokenStream(TokenStream):
__slots__ = ('tokenSource', 'tokens', 'index', 'fetchedEOF')
def __init__(self, tokenSource:Lexer):
# The {@link TokenSource} from which tokens for this stream are fetched.
self.tokenSource = tokenSource
# A collection of all tokens fetched from the token source. The list is
# considered a complete view of the input once {@link #fetchedEOF} is set
# to {@code true}.
self.tokens = []
# The index into {@link #tokens} of the current token (next token to
# {@link #consume}). {@link #tokens}{@code [}{@link #p}{@code ]} should be
# {@link #LT LT(1)}.
#
# <p>This field is set to -1 when the stream is first constructed or when
# {@link #setTokenSource} is called, indicating that the first token has
# not yet been fetched from the token source. For additional information,
# see the documentation of {@link IntStream} for a description of
# Initializing Methods.</p>
self.index = -1
# Indicates whether the {@link Token#EOF} token has been fetched from
# {@link #tokenSource} and added to {@link #tokens}. This field improves
# performance for the following cases:
#
# <ul>
# <li>{@link #consume}: The lookahead check in {@link #consume} to prevent
# consuming the EOF symbol is optimized by checking the values of
# {@link #fetchedEOF} and {@link #p} instead of calling {@link #LA}.</li>
# <li>{@link #fetch}: The check to prevent adding multiple EOF symbols into
# {@link #tokens} is trivial with this field.</li>
# <ul>
self.fetchedEOF = False
def mark(self):
return 0
def release(self, marker:int):
# no resources to release
pass
def reset(self):
self.seek(0)
def seek(self, index:int):
self.lazyInit()
self.index = self.adjustSeekIndex(index)
def get(self, index:int):
self.lazyInit()
return self.tokens[index]
def consume(self):
skipEofCheck = False
if self.index >= 0:
if self.fetchedEOF:
# the last token in tokens is EOF. skip check if p indexes any
# fetched token except the last.
skipEofCheck = self.index < len(self.tokens) - 1
else:
# no EOF token in tokens. skip check if p indexes a fetched token.
skipEofCheck = self.index < len(self.tokens)
else:
# not yet initialized
skipEofCheck = False
if not skipEofCheck and self.LA(1) == Token.EOF:
raise IllegalStateException("cannot consume EOF")
if self.sync(self.index + 1):
self.index = self.adjustSeekIndex(self.index + 1)
# Make sure index {@code i} in tokens has a token.
#
# @return {@code true} if a token is located at index {@code i}, otherwise
# {@code false}.
# @see #get(int i)
#/
def sync(self, i:int):
n = i - len(self.tokens) + 1 # how many more elements we need?
if n > 0 :
fetched = self.fetch(n)
return fetched >= n
return True
# Add {@code n} elements to buffer.
#
# @return The actual number of elements added to the buffer.
#/
def fetch(self, n:int):
if self.fetchedEOF:
return 0
for i in range(0, n):
t = self.tokenSource.nextToken()
t.tokenIndex = len(self.tokens)
self.tokens.append(t)
if t.type==Token.EOF:
self.fetchedEOF = True
return i + 1
return n
# Get all tokens from start..stop inclusively#/
def getTokens(self, start:int, stop:int, types:set=None):
if start<0 or stop<0:
return None
self.lazyInit()
subset = []
if stop >= len(self.tokens):
stop = len(self.tokens)-1
for i in range(start, stop):
t = self.tokens[i]
if t.type==Token.EOF:
break
if types is None or t.type in types:
subset.append(t)
return subset
def LA(self, i:int):
return self.LT(i).type
def LB(self, k:int):
if (self.index-k) < 0:
return None
return self.tokens[self.index-k]
def LT(self, k:int):
self.lazyInit()
if k==0:
return None
if k < 0:
return self.LB(-k)
i = self.index + k - 1
self.sync(i)
if i >= len(self.tokens): # return EOF token
# EOF must be last token
return self.tokens[len(self.tokens)-1]
return self.tokens[i]
# Allowed derived classes to modify the behavior of operations which change
# the current stream position by adjusting the target token index of a seek
# operation. The default implementation simply returns {@code i}. If an
# exception is thrown in this method, the current stream index should not be
# changed.
#
# <p>For example, {@link CommonTokenStream} overrides this method to ensure that
# the seek target is always an on-channel token.</p>
#
# @param i The target token index.
# @return The adjusted target token index.
def adjustSeekIndex(self, i:int):
return i
def lazyInit(self):
if self.index == -1:
self.setup()
def setup(self):
self.sync(0)
self.index = self.adjustSeekIndex(0)
# Reset this token stream by setting its token source.#/
def setTokenSource(self, tokenSource:Lexer):
self.tokenSource = tokenSource
self.tokens = []
self.index = -1
self.fetchedEOF = False
# Given a starting index, return the index of the next token on channel.
# Return i if tokens[i] is on channel. Return the index of the EOF token
# if there are no tokens on channel between i and EOF.
#/
def nextTokenOnChannel(self, i:int, channel:int):
self.sync(i)
if i>=len(self.tokens):
return len(self.tokens) - 1
token = self.tokens[i]
while token.channel!=channel:
if token.type==Token.EOF:
return i
i += 1
self.sync(i)
token = self.tokens[i]
return i
# Given a starting index, return the index of the previous token on channel.
# Return i if tokens[i] is on channel. Return -1 if there are no tokens
# on channel between i and 0.
def previousTokenOnChannel(self, i:int, channel:int):
while i>=0 and self.tokens[i].channel!=channel:
i -= 1
return i
# Collect all tokens on specified channel to the right of
# the current token up until we see a token on DEFAULT_TOKEN_CHANNEL or
# EOF. If channel is -1, find any non default channel token.
def getHiddenTokensToRight(self, tokenIndex:int, channel:int=-1):
self.lazyInit()
if tokenIndex<0 or tokenIndex>=len(self.tokens):
raise Exception(str(tokenIndex) + " not in 0.." + str(len(self.tokens)-1))
from antlr4.Lexer import Lexer
nextOnChannel = self.nextTokenOnChannel(tokenIndex + 1, Lexer.DEFAULT_TOKEN_CHANNEL)
from_ = tokenIndex+1
# if none onchannel to right, nextOnChannel=-1 so set to = last token
to = (len(self.tokens)-1) if nextOnChannel==-1 else nextOnChannel
return self.filterForChannel(from_, to, channel)
# Collect all tokens on specified channel to the left of
# the current token up until we see a token on DEFAULT_TOKEN_CHANNEL.
# If channel is -1, find any non default channel token.
def getHiddenTokensToLeft(self, tokenIndex:int, channel:int=-1):
self.lazyInit()
if tokenIndex<0 or tokenIndex>=len(self.tokens):
raise Exception(str(tokenIndex) + " not in 0.." + str(len(self.tokens)-1))
from antlr4.Lexer import Lexer
prevOnChannel = self.previousTokenOnChannel(tokenIndex - 1, Lexer.DEFAULT_TOKEN_CHANNEL)
if prevOnChannel == tokenIndex - 1:
return None
# if none on channel to left, prevOnChannel=-1 then from=0
from_ = prevOnChannel+1
to = tokenIndex-1
return self.filterForChannel(from_, to, channel)
def filterForChannel(self, left:int, right:int, channel:int):
hidden = []
for i in range(left, right+1):
t = self.tokens[i]
if channel==-1:
from antlr4.Lexer import Lexer
if t.channel!= Lexer.DEFAULT_TOKEN_CHANNEL:
hidden.append(t)
elif t.channel==channel:
hidden.append(t)
if len(hidden)==0:
return None
return hidden
def getSourceName(self):
return self.tokenSource.getSourceName()
# Get the text of all tokens in this buffer.#/
def getText(self, start:int=None, stop:int=None):
self.lazyInit()
self.fill()
if isinstance(start, Token):
start = start.tokenIndex
elif start is None:
start = 0
if isinstance(stop, Token):
stop = stop.tokenIndex
elif stop is None or stop >= len(self.tokens):
stop = len(self.tokens) - 1
if start < 0 or stop < 0 or stop < start:
return ""
with StringIO() as buf:
for i in range(start, stop+1):
t = self.tokens[i]
if t.type==Token.EOF:
break
buf.write(t.text)
return buf.getvalue()
# Get all tokens from lexer until EOF#/
def fill(self):
self.lazyInit()
while self.fetch(1000)==1000:
pass
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