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1######################## BEGIN LICENSE BLOCK ######################## 

2# The Original Code is mozilla.org code. 

3# 

4# The Initial Developer of the Original Code is 

5# Netscape Communications Corporation. 

6# Portions created by the Initial Developer are Copyright (C) 1998 

7# the Initial Developer. All Rights Reserved. 

8# 

9# Contributor(s): 

10# Mark Pilgrim - port to Python 

11# 

12# This library is free software; you can redistribute it and/or 

13# modify it under the terms of the GNU Lesser General Public 

14# License as published by the Free Software Foundation; either 

15# version 2.1 of the License, or (at your option) any later version. 

16# 

17# This library is distributed in the hope that it will be useful, 

18# but WITHOUT ANY WARRANTY; without even the implied warranty of 

19# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 

20# Lesser General Public License for more details. 

21# 

22# You should have received a copy of the GNU Lesser General Public 

23# License along with this library; if not, write to the Free Software 

24# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 

25# 02110-1301 USA 

26######################### END LICENSE BLOCK ######################### 

27 

28import logging 

29 

30from .codingstatemachinedict import CodingStateMachineDict 

31from .enums import MachineState 

32 

33 

34class CodingStateMachine: 

35 """ 

36 A state machine to verify a byte sequence for a particular encoding. For 

37 each byte the detector receives, it will feed that byte to every active 

38 state machine available, one byte at a time. The state machine changes its 

39 state based on its previous state and the byte it receives. There are 3 

40 states in a state machine that are of interest to an auto-detector: 

41 

42 START state: This is the state to start with, or a legal byte sequence 

43 (i.e. a valid code point) for character has been identified. 

44 

45 ME state: This indicates that the state machine identified a byte sequence 

46 that is specific to the charset it is designed for and that 

47 there is no other possible encoding which can contain this byte 

48 sequence. This will to lead to an immediate positive answer for 

49 the detector. 

50 

51 ERROR state: This indicates the state machine identified an illegal byte 

52 sequence for that encoding. This will lead to an immediate 

53 negative answer for this encoding. Detector will exclude this 

54 encoding from consideration from here on. 

55 """ 

56 

57 def __init__(self, sm: CodingStateMachineDict) -> None: 

58 self._model = sm 

59 self._curr_byte_pos = 0 

60 self._curr_char_len = 0 

61 self._curr_state = MachineState.START 

62 self.active = True 

63 self.logger = logging.getLogger(__name__) 

64 self.reset() 

65 

66 def reset(self) -> None: 

67 self._curr_state = MachineState.START 

68 

69 def next_state(self, c: int) -> int: 

70 # for each byte we get its class 

71 # if it is first byte, we also get byte length 

72 byte_class = self._model["class_table"][c] 

73 if self._curr_state == MachineState.START: 

74 self._curr_byte_pos = 0 

75 self._curr_char_len = self._model["char_len_table"][byte_class] 

76 # from byte's class and state_table, we get its next state 

77 curr_state = self._curr_state * self._model["class_factor"] + byte_class 

78 self._curr_state = self._model["state_table"][curr_state] 

79 self._curr_byte_pos += 1 

80 return self._curr_state 

81 

82 def get_current_charlen(self) -> int: 

83 return self._curr_char_len 

84 

85 def get_coding_state_machine(self) -> str: 

86 return self._model["name"] 

87 

88 @property 

89 def language(self) -> str: 

90 return self._model["language"]