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module ASN1Kit
module BERString
TAG_CLASS_MAP = {
UNIVERSAL: 0x00,
APPLICATION: 0x40,
CONTEXT_SPECIFIC: 0x80,
PRIVATE: 0xC0
}
refine(String) do
def put_object(tc, tn, len, encoding)
force_encoding("BINARY")
constructed = encoding == :constructed
if tn < 0x1f
self << (TAG_CLASS_MAP[tc] | (constructed ? 0x20 : 0x00) | tn)
else
self << (TAG_CLASS_MAP[tc] | (constructed ? 0x20 : 0x00) | 0x1f)
self << [tn].pack("w")
end
if len && len < 0x80
self << len
elsif !len
self << 0x80
else
d = len.digits(256)
self << (0x80 | d.size)
self << d.reverse.pack("C")
end
end
def put_eoc
force_encoding("BINARY")
self << 0x00
self << 0x00
end
# Returns an array: [tag_class, is_constructed, tag_number, hlen, len]
# where
# tag_class:: one of :UNIVERSAL, :APPLICATION, :CONTEXT_SPECIFIC, :PRIVATE
# is_constructed:: true of false
# tag_number:: an Integer
# hlen:: header octets length
# len:: content octets length
def get_object(offset = 0)
h = getbyte(offset) or
raise RangeError, "end of string reached"
hlen = 1
tag_class = [:UNIVERSAL, :APPLICATION, :CONTEXT_SPECIFIC, :PRIVATE][h >> 6]
constructed = h & 0x20 == 0x20
tag_number = h & 0x1f
if tag_number == 0x1f
tag_number = unpack("@#{offset + hlen} w")[0] or
raise RangeError, "end of string reached"
hlen += (tag_number.bit_length / 8r).ceil
end
len = getbyte(offset + hlen) or
raise RangeError, "end of string reached"
hlen += 1
if len > 0x80
blen = len - 0x80
d = unpack("@#{offset + hlen} C#{blen}")
d[-1] or raise RangeError, "end of string reached"
len = d.inject(0) { |sum, i| (sum << 8) + i }
hlen += blen
end
[tag_class, tag_number, constructed, hlen, len]
end
end
end
end
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