66 lines
1.8 KiB
Ruby
66 lines
1.8 KiB
Ruby
# -*- ruby encoding: utf-8 -*-
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##
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# Ber extensions to the Fixnum class.
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module Net::BER::Extensions::Fixnum
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##
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# Converts the fixnum to BER format.
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def to_ber
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"\002#{to_ber_internal}"
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end
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##
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# Converts the fixnum to BER enumerated format.
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def to_ber_enumerated
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"\012#{to_ber_internal}"
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end
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##
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# Converts the fixnum to BER length encodining format.
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def to_ber_length_encoding
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if self <= 127
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[self].pack('C')
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else
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i = [self].pack('N').sub(/^[\0]+/,"")
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[0x80 + i.length].pack('C') + i
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end
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end
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##
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# Generate a BER-encoding for an application-defined INTEGER. Examples of
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# such integers are SNMP's Counter, Gauge, and TimeTick types.
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def to_ber_application(tag)
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[0x40 + tag].pack("C") + to_ber_internal
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end
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##
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# Used to BER-encode the length and content bytes of a Fixnum. Callers
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# must prepend the tag byte for the contained value.
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def to_ber_internal
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# CAUTION: Bit twiddling ahead. You might want to shield your eyes or
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# something.
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# Looks for the first byte in the fixnum that is not all zeroes. It does
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# this by masking one byte after another, checking the result for bits
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# that are left on.
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size = Net::BER::MAX_FIXNUM_SIZE
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while size > 1
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break if (self & (0xff << (size - 1) * 8)) > 0
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size -= 1
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end
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# Store the size of the fixnum in the result
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result = [size]
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# Appends bytes to result, starting with higher orders first. Extraction
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# of bytes is done by right shifting the original fixnum by an amount
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# and then masking that with 0xff.
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while size > 0
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# right shift size - 1 bytes, mask with 0xff
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result << ((self >> ((size - 1) * 8)) & 0xff)
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size -= 1
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end
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result.pack('C*')
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end
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private :to_ber_internal
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end
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