Class: HexaPDF::Type::Trailer

Inherits:
Dictionary show all
Defined in:
lib/hexapdf/type/trailer.rb

Overview

Represents the PDF file trailer.

The file trailer is the starting point for the PDF’s object tree. It links to the Catalog (the main PDF document structure) and the Info dictionary and holds the information necessary for encrypting the PDF document.

Since a PDF document can contain multiple revisions, each revision needs to have its own file trailer (see HexaPDF::Revision#trailer).

When cross-reference streams are used the information that is normally stored in the file trailer is stored directly in the cross-reference stream dictionary. However, a HexaPDF::Revision object’s trailer dictionary is always of this type. Only when a cross-reference stream is written is the trailer integrated into the stream’s dictionary.

See: PDF2.0 s7.5.5, s14.4; XRefStream

Constant Summary

Constants included from DictionaryFields

DictionaryFields::Boolean, DictionaryFields::PDFByteString, DictionaryFields::PDFDate

Instance Attribute Summary

Attributes inherited from Object

#data, #document, #must_be_indirect

Instance Method Summary collapse

Methods inherited from Dictionary

#[], #[]=, define_field, define_type, #delete, #each, each_field, #empty?, field, #key?, #to_hash, type, #type

Methods inherited from Object

#<=>, #==, #cache, #cached?, #clear_cache, deep_copy, #deep_copy, #document?, #eql?, field, #gen, #gen=, #hash, #indirect?, #initialize, #inspect, make_direct, #must_be_indirect?, #null?, #oid, #oid=, #type, #validate, #value, #value=

Constructor Details

This class inherits a constructor from HexaPDF::Object

Instance Method Details

#catalog ⇒ Object

Returns the document’s Catalog (see Type::Catalog), creating it if needed.



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# File 'lib/hexapdf/type/trailer.rb', line 71

def catalog
  self[:Root] ||= document.add({Type: :Catalog}, type: :Catalog)
end

#info ⇒ Object

Returns the document’s information dictionary (see Type::Info), creating it if needed.



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# File 'lib/hexapdf/type/trailer.rb', line 76

def info
  self[:Info] ||= document.add({}, type: :XXInfo)
end

#set_random_id ⇒ Object

Sets the /ID field to an array of two copies of a random string and returns this array.

See: PDF2.0 14.4



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# File 'lib/hexapdf/type/trailer.rb', line 83

def set_random_id
  value[:ID] = [Digest::MD5.digest(rand.to_s)] * 2
end

#update_id ⇒ Object

Updates the second part of the /ID field (the first part should always be the same for a PDF file, the second part should change with each write).



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# File 'lib/hexapdf/type/trailer.rb', line 89

def update_id
  if self[:ID].kind_of?(PDFArray)
    value[:ID][1] = Digest::MD5.digest(rand.to_s)
  else
    set_random_id
  end
end