64 lines
1.8 KiB
Ruby
64 lines
1.8 KiB
Ruby
require 'bit-struct/bit-struct'
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class BitStruct
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# Class for null-terminated printable text strings.
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# Declared with BitStruct.text.
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class TextField < Field
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# Used in describe.
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def self.class_name
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@class_name ||= "text"
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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 % 8 == 0
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raise ArgumentError,
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"Bad length, #{length}, for #{self.class} #{name}." +
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" Must be multiple of 8."
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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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val_byte_range = 0..length_byte-1
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cl.class_eval do
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define_method attr do ||
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self[byte_range].sub(/\0*$/, "").to_s
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end
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define_method "#{attr}=" do |val|
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val = val.to_s
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if val.length < length_byte
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val += "\0" * (length_byte - val.length)
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end
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self[byte_range] = val[val_byte_range]
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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 printable text string field in the current subclass of BitStruct,
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# with the given _name_ and _length_ (in bits). Trailing nulls are
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# _not_ considered part of the string.
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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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# Note that the accessors have COPY semantics, not reference.
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#
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def text(name, length, *rest)
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opts = parse_options(rest, name, TextField)
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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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