Class: Resilience::Page

Inherits:
Object
  • Object
show all
Includes:
OnImage
Defined in:
lib/resilience/page.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from OnImage

#image, image, included, restore_pos, #restore_pos, store_pos, #store_pos

Constructor Details

#initialize ⇒ Page

Returns a new instance of Page.



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# File 'lib/resilience/page.rb', line 22

def initialize
  @attributes ||= []
end

Instance Attribute Details

#attributes ⇒ Object

Returns the value of attribute attributes.



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# File 'lib/resilience/page.rb', line 17

def attributes
  @attributes
end

#contents ⇒ Object

Returns the value of attribute contents.



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# File 'lib/resilience/page.rb', line 12

def contents
  @contents
end

#entries ⇒ Object

Returns the value of attribute entries.



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# File 'lib/resilience/page.rb', line 20

def entries
  @entries
end

#id ⇒ Object

Returns the value of attribute id.



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# File 'lib/resilience/page.rb', line 11

def id
  @id
end

#object_id ⇒ Object

Returns the value of attribute object_id.



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# File 'lib/resilience/page.rb', line 19

def object_id
  @object_id
end

#sequence ⇒ Object

Returns the value of attribute sequence.



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# File 'lib/resilience/page.rb', line 14

def sequence
  @sequence
end

#virtual_page_number ⇒ Object

Returns the value of attribute virtual_page_number.



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# File 'lib/resilience/page.rb', line 15

def virtual_page_number
  @virtual_page_number
end

Class Method Details

.extract_all ⇒ Object 



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# File 'lib/resilience/page.rb', line 26

def self.extract_all
  page_id     = PAGES[:first]
  pages       = Pages.new

  image.seek(page_id * PAGE_SIZE)
  while contents = image.read(PAGE_SIZE)
    # only pull out metadata pages currently
    extracted_id   = id_from_contents(contents)
    is_metadata    = extracted_id == page_id
    pages[page_id] = Page.parse(page_id, contents) if is_metadata
    page_id       += 1
  end

  pages
end

.id_from_contents(contents) ⇒ Object 



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# File 'lib/resilience/page.rb', line 42

def self.id_from_contents(contents)
  contents.unpack('S').first
end

.parse(id, contents) ⇒ Object 



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# File 'lib/resilience/page.rb', line 62

def self.parse(id, contents)
  store_pos

  page          = new
  page.id       = id
  page.contents = contents

  image.seek(page.offset + ADDRESSES[:page_sequence])
  page.sequence = image.read(4).unpack('L').first

  image.seek(page.offset + ADDRESSES[:virtual_page_number])
  page.virtual_page_number = image.read(4).unpack('L').first

  unless page.root? || page.object_table?
    # TODO:
    #page.parse_attributes
    #page.parse_metadata
  end

  restore_pos

  page
end

Instance Method Details

#attr_start ⇒ Object 



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# File 'lib/resilience/page.rb', line 50

def attr_start
  offset + ADDRESSES[:first_attr]
end

#has_attributes? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/resilience/page.rb', line 86

def has_attributes?
  !@attributes.nil? && !@attributes.empty?
end

#object_table? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/resilience/page.rb', line 58

def object_table?
  virtual_page_number == PAGES[:object_table]
end

#offset ⇒ Object 



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# File 'lib/resilience/page.rb', line 46

def offset
  id * PAGE_SIZE
end

#parse_attributes ⇒ Object 



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# File 'lib/resilience/page.rb', line 90

def parse_attributes
  image.seek(attr_start)
  while true
    attr = Attribute.read
    break if attr.empty?
    @attributes << attr
  end
end

#parse_metadata ⇒ Object 



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# File 'lib/resilience/page.rb', line 99

def parse_metadata
  @object_id = @attributes.first.unpack("C*")[ADDRESSES[:object_id]]
  @entries   = @attributes.first.unpack("C*")[ADDRESSES[:num_objects]]
end

#root? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/resilience/page.rb', line 54

def root?
  virtual_page_number == PAGES[:root]
end