105 lines
2.7 KiB
Python
105 lines
2.7 KiB
Python
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#
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# Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
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# Use of this file is governed by the BSD 3-clause license that
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# can be found in the LICENSE.txt file in the project root.
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#
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import unittest
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#
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# Vacuum all input from a string and then treat it like a buffer.
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#
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from antlr4.Token import Token
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class InputStream (object):
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def __init__(self, data: str):
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self.name = "<empty>"
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self.strdata = data
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self._loadString()
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def _loadString(self):
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self._index = 0
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self.data = [ord(c) for c in self.strdata]
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self._size = len(self.data)
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@property
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def index(self):
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return self._index
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@property
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def size(self):
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return self._size
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# Reset the stream so that it's in the same state it was
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# when the object was created *except* the data array is not
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# touched.
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#
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def reset(self):
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self._index = 0
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def consume(self):
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if self._index >= self._size:
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assert self.LA(1) == Token.EOF
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raise Exception("cannot consume EOF")
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self._index += 1
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def LA(self, offset: int):
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if offset==0:
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return 0 # undefined
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if offset<0:
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offset += 1 # e.g., translate LA(-1) to use offset=0
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pos = self._index + offset - 1
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if pos < 0 or pos >= self._size: # invalid
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return Token.EOF
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return self.data[pos]
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def LT(self, offset: int):
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return self.LA(offset)
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# mark/release do nothing; we have entire buffer
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def mark(self):
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return -1
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def release(self, marker: int):
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pass
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# consume() ahead until p==_index; can't just set p=_index as we must
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# update line and column. If we seek backwards, just set p
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#
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def seek(self, _index: int):
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if _index<=self._index:
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self._index = _index # just jump; don't update stream state (line, ...)
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return
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# seek forward
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self._index = min(_index, self._size)
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def getText(self, start :int, stop: int):
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if stop >= self._size:
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stop = self._size-1
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if start >= self._size:
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return ""
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else:
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return self.strdata[start:stop+1]
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def __str__(self):
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return self.strdata
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class TestInputStream(unittest.TestCase):
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def testStream(self):
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stream = InputStream("abcde")
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self.assertEqual(0, stream.index)
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self.assertEqual(5, stream.size)
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self.assertEqual(ord("a"), stream.LA(1))
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stream.consume()
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self.assertEqual(1, stream.index)
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stream.seek(5)
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self.assertEqual(Token.EOF, stream.LA(1))
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self.assertEqual("bcd", stream.getText(1, 3))
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stream.reset()
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self.assertEqual(0, stream.index)
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