90 lines
2.8 KiB
Ruby
90 lines
2.8 KiB
Ruby
# $Id: tlv.rb 14 2008-03-02 05:42:30Z warchild $
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#
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# Copyright (c) 2008, Jon Hart
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# * Neither the name of the <organization> nor the
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# names of its contributors may be used to endorse or promote products
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# derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY Jon Hart ``AS IS'' AND ANY
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# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL Jon Hart BE LIABLE FOR ANY
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# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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# Simple class for your average type, length, value datastructure.
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# Everything after the TLV is stuff into +rest+
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module Racket
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class TLV
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attr_accessor :type, :length, :value, :rest
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# Create a new TLV which requires +ts+ bytes for the type field
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# and +ls+ bytes for the length field
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def initialize(ts, ls)
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@ts = ts
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@ls = ls
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end
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# Given +data+, return the type, length, value and rest
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# values as dictated by this instance.
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def decode(data)
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s = "#{punpack_string(@ts)}#{punpack_string(@ls)}"
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type, length, tmp = data.unpack("#{s}a*")
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value, rest = tmp.unpack("a#{length}a*")
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[type, length, value, rest]
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end
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def decode!(data)
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@type, @length, @value, @rest = self.decode(data)
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end
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# Return a string suitable for use elswhere.
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def encode
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s = "#{punpack_string(@ts)}#{punpack_string(@ls)}"
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[@type, @length, @value].pack("#{s}a*")
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end
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def to_s
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encode
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end
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def to_str
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encode
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end
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private
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# XXX: make this handle arbitrarily sized fields
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def punpack_string(size)
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s = ""
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case size
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when 1
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s << "C"
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when 2
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s << "n"
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when 4
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s << "N"
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else
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puts "Size #{s} not supported"
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exit
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end
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s
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end
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end
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end
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# vim: set ts=2 et sw=2:
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