Class: HexaPDF::Reference

Inherits:
Object
  • Object
show all
Includes:
Comparable
Defined in:
lib/hexapdf/reference.rb

Overview

A reference to an indirect object.

The PDF syntax allows for references to existing and non-existing indirect objects. Such references are represented with objects of this class.

Note that after initialization changing the object or generation numbers is not possible anymore!

The methods #hash and #eql? are implemented so that objects of this class can be used as hash keys. Furthermore the implementation is compatible to the one of Object, i.e. the hash of a Reference object is the same as the hash of an indirect Object.

See: PDF2.0 s7.3.10, Object

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(oid, gen = 0) ⇒ Reference

Creates a new Reference with the given object number and, optionally, generation number.



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# File 'lib/hexapdf/reference.rb', line 65

def initialize(oid, gen = 0)
  @oid = Integer(oid)
  @gen = Integer(gen)
end

Instance Attribute Details

#gen ⇒ Object (readonly)

Returns the generation number of the referenced indirect object.



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# File 'lib/hexapdf/reference.rb', line 62

def gen
  @gen
end

#oid ⇒ Object (readonly)

Returns the object number of the referenced indirect object.



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# File 'lib/hexapdf/reference.rb', line 59

def oid
  @oid
end

Instance Method Details

#<=>(other) ⇒ Object

Compares this object to another object.

If the other object does not respond to oid or gen, nil is returned. Otherwise objects are ordered first by object number and then by generation number.



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# File 'lib/hexapdf/reference.rb', line 74

def <=>(other)
  return nil unless other.respond_to?(:oid) && other.respond_to?(:gen)
  (oid == other.oid ? gen <=> other.gen : oid <=> other.oid)
end

#eql?(other) ⇒ Boolean Also known as: ==

Returns true if the other object references the same PDF object as this reference object.

This is necessary so that Object and Reference objects can be used as interchangable hash keys and can be compared.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/reference.rb', line 83

def eql?(other)
  other.respond_to?(:oid) && oid == other.oid && other.respond_to?(:gen) && gen == other.gen
end

#hash ⇒ Object

Computes the hash value based on the object and generation numbers.



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# File 'lib/hexapdf/reference.rb', line 89

def hash
  [oid, gen].hash
end

#inspect ⇒ Object

:nodoc:



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# File 'lib/hexapdf/reference.rb', line 98

def inspect #:nodoc:
  "#<#{self.class.name} [#{oid}, #{gen}]>"
end

#to_s ⇒ Object

Returns the object identifier as “oid,gen”.



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# File 'lib/hexapdf/reference.rb', line 94

def to_s
  "#{oid} #{gen} R"
end