Class: Tamper::ExistencePack

Inherits:
Pack
  • Object
show all
Defined in:
lib/tamper/existence_pack.rb

Instance Attribute Summary

Attributes inherited from Pack

#attr_name, #bit_window_width, #bitset, #item_window_width, #max_choices, #max_guid, #meta, #possibilities

Instance Method Summary collapse

Methods inherited from Pack

build

Constructor Details

#initialize ⇒ ExistencePack

Returns a new instance of ExistencePack.



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# File 'lib/tamper/existence_pack.rb', line 4

def initialize
  @output = ''
  @current_chunk = ''
  @last_guid   = 0
  @run_counter = 0
end

Instance Method Details

#encode(guid) ⇒ Object 



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# File 'lib/tamper/existence_pack.rb', line 18

def encode(guid)
  guid_diff  = guid.to_i - @last_guid
  guid_diff += 1 if @current_chunk.empty? && @output.empty? && guid.to_i > 0

  if guid_diff == 1 || guid.to_i == 0  # guid is 1 step forward
    @current_chunk << '1'
    @run_counter += 1

  elsif guid_diff <= 0  # somehow we went backwards or didn't change guid on iteration
    raise ArgumentError, "Error: data was not sorted by GUID (got #{@last_guid}, then #{guid})!"

  elsif guid_diff > 40  # big gap, encode with skip control char
    dump_keep(@current_chunk, @run_counter)

    @output += control_code(:skip, guid_diff - 1)
    @current_chunk = '1'
    @run_counter   = 1

  else # skips < 40 should just be encoded as '0'
    if @run_counter > 40    # first check if a run came before this 0; if so dump it
      dump_keep(@current_chunk, @run_counter)
      @current_chunk = ''
      @run_counter = 0
    end

    @current_chunk += ('0' * (guid_diff - 1))
    @current_chunk << '1'
    @run_counter = 1
  end

  @last_guid = guid.to_i
end

#encoding ⇒ Object 



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# File 'lib/tamper/existence_pack.rb', line 14

def encoding
  :existence
end

#finalize_pack! ⇒ Object 



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# File 'lib/tamper/existence_pack.rb', line 51

def finalize_pack!
  dump_keep(@current_chunk, @run_counter)
  raise "Encoding error, #{@output.length} is not an even number of bytes!" if @output.length % 8 > 0
  @bitset = Bitset.from_s(@output)
end

#initialize_pack!(max_guid, num_items) ⇒ Object 



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# File 'lib/tamper/existence_pack.rb', line 11

def initialize_pack!(max_guid, num_items)
end

#to_h ⇒ Object 



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# File 'lib/tamper/existence_pack.rb', line 57

def to_h
  { encoding: encoding,
    pack: encoded_bitset }
end