83 lines
2.2 KiB
Ruby
83 lines
2.2 KiB
Ruby
require 'bit-struct/bit-struct'
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class BitStruct
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# Class for floats (single and double precision) in network order.
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# Declared with BitStruct.float.
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class FloatField < Field
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# Used in describe.
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def self.class_name
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@class_name ||= "float"
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end
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def add_accessors_to(cl, attr = name) # :nodoc:
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unless offset % 8 == 0
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raise ArgumentError,
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"Bad offset, #{offset}, for #{self.class} #{name}." +
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" Must be multiple of 8."
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end
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unless length == 32 or length == 64
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raise ArgumentError,
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"Bad length, #{length}, for #{self.class} #{name}." +
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" Must be 32 or 64."
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end
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offset_byte = offset / 8
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length_byte = length / 8
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last_byte = offset_byte + length_byte - 1
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byte_range = offset_byte..last_byte
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endian = (options[:endian] || options["endian"]).to_s
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case endian
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when "native"
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ctl = case length
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when 32; "f"
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when 64; "d"
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end
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when "little"
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ctl = case length
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when 32; "e"
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when 64; "E"
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end
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when "network", "big", ""
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ctl = case length
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when 32; "g"
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when 64; "G"
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end
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else
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raise ArgumentError,
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"Unrecognized endian option: #{endian.inspect}"
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end
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cl.class_eval do
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define_method attr do ||
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self[byte_range].unpack(ctl).first
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end
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define_method "#{attr}=" do |val|
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self[byte_range] = [val].pack(ctl)
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end
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end
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end
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end
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class << self
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# Define a floating point field in the current subclass of BitStruct,
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# with the given _name_ and _length_ (in bits).
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#
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# If a class is provided, use it for the Field class.
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# If a string is provided, use it for the display_name.
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# If a hash is provided, use it for options.
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#
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# The <tt>:endian => :native</tt> option overrides the default of
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# <tt>:network</tt> byte ordering, in favor of native byte ordering. Also
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# permitted are <tt>:big</tt> (same as <tt>:network</tt>) and
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# <tt>:little</tt>.
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#
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def float name, length, *rest
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opts = parse_options(rest, name, FloatField)
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add_field(name, length, opts)
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end
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end
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end
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