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89 lines
3.5 KiB
Python
89 lines
3.5 KiB
Python
######################## BEGIN LICENSE BLOCK ########################
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# The Original Code is mozilla.org code.
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#
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# The Initial Developer of the Original Code is
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# Netscape Communications Corporation.
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# Portions created by the Initial Developer are Copyright (C) 1998
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# the Initial Developer. All Rights Reserved.
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#
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# Contributor(s):
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# Mark Pilgrim - port to Python
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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# 02110-1301 USA
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######################### END LICENSE BLOCK #########################
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import logging
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from .enums import MachineState
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class CodingStateMachine:
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"""
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A state machine to verify a byte sequence for a particular encoding. For
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each byte the detector receives, it will feed that byte to every active
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state machine available, one byte at a time. The state machine changes its
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state based on its previous state and the byte it receives. There are 3
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states in a state machine that are of interest to an auto-detector:
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START state: This is the state to start with, or a legal byte sequence
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(i.e. a valid code point) for character has been identified.
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ME state: This indicates that the state machine identified a byte sequence
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that is specific to the charset it is designed for and that
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there is no other possible encoding which can contain this byte
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sequence. This will to lead to an immediate positive answer for
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the detector.
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ERROR state: This indicates the state machine identified an illegal byte
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sequence for that encoding. This will lead to an immediate
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negative answer for this encoding. Detector will exclude this
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encoding from consideration from here on.
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"""
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def __init__(self, sm):
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self._model = sm
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self._curr_byte_pos = 0
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self._curr_char_len = 0
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self._curr_state = None
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self.logger = logging.getLogger(__name__)
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self.reset()
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def reset(self):
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self._curr_state = MachineState.START
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def next_state(self, c):
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# for each byte we get its class
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# if it is first byte, we also get byte length
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byte_class = self._model["class_table"][c]
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if self._curr_state == MachineState.START:
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self._curr_byte_pos = 0
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self._curr_char_len = self._model["char_len_table"][byte_class]
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# from byte's class and state_table, we get its next state
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curr_state = self._curr_state * self._model["class_factor"] + byte_class
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self._curr_state = self._model["state_table"][curr_state]
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self._curr_byte_pos += 1
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return self._curr_state
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def get_current_charlen(self):
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return self._curr_char_len
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def get_coding_state_machine(self):
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return self._model["name"]
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@property
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def language(self):
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return self._model["language"]
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