1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
# frozen_string_literal: true
# This file is part of the ruby-dbus project
# Copyright (C) 2022 Martin Vidner
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License, version 2.1 as published by the Free Software Foundation.
# See the file "COPYING" for the exact licensing terms.
module DBus
# A message while it is being parsed: a binary string,
# with a position cursor (*pos*), and an *endianness* tag.
class RawMessage
# @return [String]
# attr_reader :bytes
# @return [Integer] position in the byte buffer
attr_reader :pos
# @return [:little,:big]
attr_reader :endianness
# @param bytes [String]
# @param endianness [:little,:big,nil]
# if not given, read the 1st byte of *bytes*
def initialize(bytes, endianness = nil)
@bytes = bytes
@pos = 0
@endianness = endianness || self.class.endianness(@bytes[0])
end
# Get the endiannes switch as a Symbol,
# which will make using it slightly more efficient
# @param tag_char [String]
# @return [:little,:big]
def self.endianness(tag_char)
case tag_char
when LIL_END
:little
when BIG_END
:big
else
raise InvalidPacketException, "Incorrect endianness #{tag_char.inspect}"
end
end
# @return [void]
# @raise IncompleteBufferException if there are not enough bytes remaining
def want!(size)
raise IncompleteBufferException if @pos + size > @bytes.bytesize
end
# @return [String]
# @raise IncompleteBufferException if there are not enough bytes remaining
# TODO: stress test this with encodings. always binary?
def read(size)
want!(size)
ret = @bytes.slice(@pos, size)
@pos += size
ret
end
# @return [String]
# @api private
def remaining_bytes
# This returns "" if pos is just past the end of the string,
# and nil if it is further.
@bytes[@pos..-1]
end
# Align the *pos* index on a multiple of *alignment*
# @param alignment [Integer] must be 1, 2, 4 or 8
# @return [void]
def align(alignment)
case alignment
when 1
nil
when 2, 4, 8
bits = alignment - 1
pad_size = ((@pos + bits) & ~bits) - @pos
pad = read(pad_size)
unless pad.bytes.all?(&:zero?)
raise InvalidPacketException, "Alignment bytes are not NUL"
end
else
raise ArgumentError, "Unsupported alignment #{alignment}"
end
end
end
end
|
