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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. | |
| # | |
| import unittest | |
| # | |
| # Vacuum all input from a string and then treat it like a buffer. | |
| # | |
| from antlr4.Token import Token | |
| class InputStream (object): | |
| def __init__(self, data: str): | |
| self.name = "<empty>" | |
| self.strdata = data | |
| self._loadString() | |
| def _loadString(self): | |
| self._index = 0 | |
| self.data = [ord(c) for c in self.strdata] | |
| self._size = len(self.data) | |
| def index(self): | |
| return self._index | |
| def size(self): | |
| return self._size | |
| # Reset the stream so that it's in the same state it was | |
| # when the object was created *except* the data array is not | |
| # touched. | |
| # | |
| def reset(self): | |
| self._index = 0 | |
| def consume(self): | |
| if self._index >= self._size: | |
| assert self.LA(1) == Token.EOF | |
| raise Exception("cannot consume EOF") | |
| self._index += 1 | |
| def LA(self, offset: int): | |
| if offset==0: | |
| return 0 # undefined | |
| if offset<0: | |
| offset += 1 # e.g., translate LA(-1) to use offset=0 | |
| pos = self._index + offset - 1 | |
| if pos < 0 or pos >= self._size: # invalid | |
| return Token.EOF | |
| return self.data[pos] | |
| def LT(self, offset: int): | |
| return self.LA(offset) | |
| # mark/release do nothing; we have entire buffer | |
| def mark(self): | |
| return -1 | |
| def release(self, marker: int): | |
| pass | |
| # consume() ahead until p==_index; can't just set p=_index as we must | |
| # update line and column. If we seek backwards, just set p | |
| # | |
| def seek(self, _index: int): | |
| if _index<=self._index: | |
| self._index = _index # just jump; don't update stream state (line, ...) | |
| return | |
| # seek forward | |
| self._index = min(_index, self._size) | |
| def getText(self, start :int, stop: int): | |
| if stop >= self._size: | |
| stop = self._size-1 | |
| if start >= self._size: | |
| return "" | |
| else: | |
| return self.strdata[start:stop+1] | |
| def __str__(self): | |
| return self.strdata | |
| class TestInputStream(unittest.TestCase): | |
| def testStream(self): | |
| stream = InputStream("abcde") | |
| self.assertEqual(0, stream.index) | |
| self.assertEqual(5, stream.size) | |
| self.assertEqual(ord("a"), stream.LA(1)) | |
| stream.consume() | |
| self.assertEqual(1, stream.index) | |
| stream.seek(5) | |
| self.assertEqual(Token.EOF, stream.LA(1)) | |
| self.assertEqual("bcd", stream.getText(1, 3)) | |
| stream.reset() | |
| self.assertEqual(0, stream.index) | |