Class: BitStruct::Field

Inherits:
Object
  • Object
show all
Defined in:
lib/bit-struct/bit-struct.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(offset, length, name, opts = {}) ⇒ Field

Options are display_name, default, and format (subclasses of Field may add other options).



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# File 'lib/bit-struct/bit-struct.rb', line 78

def initialize(offset, length, name, opts = {})
  @offset, @length, @name, @options =
    offset, length, name, opts
  
  @display_name = opts[:display_name] || opts["display_name"]
  @default      = opts[:default] || opts["default"] || self.class.default
  @format       = opts[:format] || opts["format"]
end

Instance Attribute Details

#default ⇒ Object (readonly)

Default value.



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# File 'lib/bit-struct/bit-struct.rb', line 33

def default
  @default
end

#display_name ⇒ Object (readonly)

Display name of field (used for printing).



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# File 'lib/bit-struct/bit-struct.rb', line 30

def display_name
  @display_name
end

#format ⇒ Object (readonly)

Format for printed value of field.



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# File 'lib/bit-struct/bit-struct.rb', line 36

def format
  @format
end

#length ⇒ Object (readonly) Also known as: size

Length of field in bits.



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# File 'lib/bit-struct/bit-struct.rb', line 19

def length
  @length
end

#name ⇒ Object (readonly)

Name of field (used for its accessors).



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# File 'lib/bit-struct/bit-struct.rb', line 23

def name
  @name
end

#offset ⇒ Object (readonly)

Offset of field in bits.



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# File 'lib/bit-struct/bit-struct.rb', line 16

def offset
  @offset
end

#options ⇒ Object (readonly)

Options, such as :default (varies for each field subclass). In general, options can be provided as strings or as symbols.



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# File 'lib/bit-struct/bit-struct.rb', line 27

def options
  @options
end

Class Method Details

.class_name ⇒ Object

Used in describe.



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# File 'lib/bit-struct/bit-struct.rb', line 47

def self.class_name
  @class_name ||= name[/\w+$/]
end

.default ⇒ Object

Subclasses can override this to define a default for all fields of this class, not just the one currently being added to a BitStruct class, a “default default” if you will. The global default, if #default returns nil, is to fill the field with zero. Most field classes just let this default stand. The default can be overridden per-field when a BitStruct class is defined.



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# File 'lib/bit-struct/bit-struct.rb', line 44

def self.default; nil; end

Instance Method Details

#class_name ⇒ Object

Used in describe. Can be overridden per-subclass, as in NestedField.



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# File 'lib/bit-struct/bit-struct.rb', line 52

def class_name
  self.class.class_name
end

#describe(opts) {|["@%d" % byte_offset, class_name, name, len_str, display_name]| ... } ⇒ Object

Yield the description of this field, as an array of 5 strings: byte offset, type, name, size, and description. The opts hash may have:

:expand

if the value is true, expand complex fields

(Subclass implementations may yield more than once for complex fields.)

Yields:



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# File 'lib/bit-struct/bit-struct.rb', line 63

def describe opts
  bits = size
  if bits > 32 and bits % 8 == 0
    len_str = "%dB" % (bits/8)
  else
    len_str = "%db" % bits
  end
  
  byte_offset = offset / 8 + (opts[:byte_offset] || 0)

  yield ["@%d" % byte_offset, class_name, name, len_str, display_name]
end

#inspect_in_object(obj, opts) ⇒ Object

Inspect the value of this field in the specified obj.



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# File 'lib/bit-struct/bit-struct.rb', line 88

def inspect_in_object(obj, opts)
  val = obj.send(name)
  str =
    begin
      val.inspect(opts)
    rescue ArgumentError # assume: "wrong number of arguments (1 for 0)"
      val.inspect
    end
  (f=@format) ? (f % str) : str
end

#inspectable? ⇒ Boolean

Normally, all fields show up in inspect, but some, such as padding, should not.

Returns:

  • (Boolean) 


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# File 'lib/bit-struct/bit-struct.rb', line 101

def inspectable?; true; end