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
|
# -*- ruby encoding: utf-8 -*-
##
# BER extensions to the Integer class, affecting Fixnum and Bignum objects.
module Net::BER::Extensions::Integer
##
# Converts the Integer to BER format.
def to_ber
"\002#{to_ber_internal}"
end
##
# Converts the Integer to BER enumerated format.
def to_ber_enumerated
"\012#{to_ber_internal}"
end
##
# Converts the Integer to BER length encoding format.
def to_ber_length_encoding
if self <= 127
[self].pack('C')
else
i = [self].pack('N').sub(/^[\0]+/, "")
[0x80 + i.length].pack('C') + i
end
end
##
# Generate a BER-encoding for an application-defined INTEGER. Examples of
# such integers are SNMP's Counter, Gauge, and TimeTick types.
def to_ber_application(tag)
[0x40 + tag].pack("C") + to_ber_internal
end
##
# Used to BER-encode the length and content bytes of an Integer. Callers
# must prepend the tag byte for the contained value.
def to_ber_internal
# Compute the byte length, accounting for negative values requiring two's
# complement.
size = 1
size += 1 until (((self < 0) ? ~self : self) >> (size * 8)).zero?
# Padding for positive, negative values. See section 8.5 of ITU-T X.690:
# http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
# For positive integers, if most significant bit in an octet is set to one,
# pad the result (otherwise it's decoded as a negative value).
if self > 0 && (self & (0x80 << (size - 1) * 8)) > 0
size += 1
end
# And for negative integers, pad if the most significant bit in the octet
# is not set to one (othwerise, it's decoded as positive value).
if self < 0 && (self & (0x80 << (size - 1) * 8)) == 0
size += 1
end
# Store the size of the Integer in the result
result = [size]
# Appends bytes to result, starting with higher orders first. Extraction
# of bytes is done by right shifting the original Integer by an amount
# and then masking that with 0xff.
while size > 0
# right shift size - 1 bytes, mask with 0xff
result << ((self >> ((size - 1) * 8)) & 0xff)
size -= 1
end
result.pack('C*')
end
private :to_ber_internal
end
|
