Coverage for d7a/dll/parser.py: 91%

46 statements  

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1# 

2# Copyright (c) 2015-2021 University of Antwerp, Aloxy NV. 

3# 

4# This file is part of pyd7a. 

5# See https://github.com/Sub-IoT/pyd7a for further info. 

6# 

7# Licensed under the Apache License, Version 2.0 (the "License"); 

8# you may not use this file except in compliance with the License. 

9# You may obtain a copy of the License at 

10# 

11# http://www.apache.org/licenses/LICENSE-2.0 

12# 

13# Unless required by applicable law or agreed to in writing, software 

14# distributed under the License is distributed on an "AS IS" BASIS, 

15# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 

16# See the License for the specific language governing permissions and 

17# limitations under the License. 

18# 

19from enum import Enum 

20 

21from bitstring import ConstBitStream, ReadError 

22 

23from d7a.dll.background_frame import BackgroundFrame 

24from d7a.dll.foreground_frame import ForegroundFrame 

25 

26class ParseError(Exception): pass 

27 

28class FrameType(Enum): 

29 FOREGROUND = 0 

30 BACKGROUND = 1 

31 

32class Parser(object): 

33 

34 def __init__(self, frame_type): 

35 self.buffer = [] 

36 self.frame_type = frame_type 

37 

38 def parse(self, frame): 

39 self.buffer.extend(frame) 

40 return self.parse_buffer() 

41 

42 def parse_buffer(self): 

43 parsed = 0 

44 frames = [] 

45 

46 (frame, info) = self.parse_one_frame_from_buffer() 

47 parsed += info["parsed"] 

48 frames.append(frame) 

49 # TODO loop 

50 # while True: 

51 # (frame, info) = self.parse_one_frame_from_buffer() 

52 # if frame is None: break 

53 # parsed += info["parsed"] 

54 # frames.append(frame) 

55 

56 info["parsed"] = parsed 

57 return (self.frame_type, frames, info) 

58 

59 def shift_buffer(self, start: int): 

60 self.buffer = self.buffer[start:] 

61 return self 

62 

63 def parse_one_frame_from_buffer(self): 

64 retry = True # until we have one or don't have enough 

65 errors = [] 

66 frame = None 

67 bits_parsed = 0 

68 while retry and len(self.buffer) > 0: 

69 try: 

70 self.s = ConstBitStream(bytes=self.buffer) 

71 if self.frame_type == FrameType.FOREGROUND: 

72 frame = ForegroundFrame.parse(self.s) 

73 else: 

74 frame = BackgroundFrame.parse(self.s) 

75 bits_parsed = self.s.pos 

76 self.shift_buffer(bits_parsed//8) 

77 retry = False # got one, carry on 

78 except ReadError as e: # not enough to read, carry on and wait for more 

79 retry = False 

80 except ParseError as e: # actual problem with current buffer, need to skip 

81 errors.append({ 

82 "error" : e.args[0], 

83 "buffer" : list(self.buffer), 

84 "pos" : self.s.pos, 

85 "skipped" : self.skip_bad_buffer_content() 

86 }) 

87 

88 info = { 

89 "parsed" : bits_parsed, 

90 "buffer" : len(self.buffer) * 8, 

91 "errors" : errors 

92 } 

93 return (frame, info) 

94 

95 

96 

97