Class: Oneliner::SuperString

Inherits:
String
  • Object
show all
Defined in:
lib/oneliner/superstring.rb

Overview

A String subclass providing Online Code functionality.

Constant Summary collapse

E = 
0.01
Q = 
3
F = 
(Math.log((E ** 2) / 4) / Math.log(1 - (E / 2))).abs.to_i
P = 
[0, (1 - ((1 + (1 / F)) / (1 + E)))]

Instance Method Summary collapse

Instance Method Details

#decode!(chunk) ⇒ Object

Will try to decode this SuperString using the given chunk and all formerly given chunks.

Returns whether decoding is done.



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# File 'lib/oneliner/superstring.rb', line 67

def decode!(chunk)
  raise "#{chunk.inspect} is too small for metadata (8 bytes)" unless chunk.size > 7

  @decode_done = nil

  context = Context.new

  requested_size = chunk[0..3].unpack("i").first

  ensure_decode_format(requested_size)

  the_seed = chunk[4..7].unpack("i").first

  chunk_data = build_chunk_data(chunk, context, the_seed)
  
  @known_nr_of_blocks += chunk_data.size
  @known_chunks.unshift(chunk_data)

  if @known_nr_of_blocks > @nr_of_blocks

    nil while do_decode(context)
    
    if decode_done?
      self.replace(compact(@blocks[0...@nr_of_data_blocks])[0...requested_size])
      return true
    else
      return false
    end
    
  else
    return false
  end
end

#decode_done? ⇒ Boolean

Returns whether decoding is done.

Returns:

  • (Boolean) 


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# File 'lib/oneliner/superstring.rb', line 104

def decode_done?
  return false unless defined?(@decode_done) && defined?(@nr_of_data_blocks)

  unless @decode_done
    data = @blocks[0...@nr_of_data_blocks]
    @decode_done = data.compact.size == data.size
  end
  return @decode_done
end

#encode(requested_size) ⇒ Object

Will return a String containing requested_size nr of bytes as an online coded chunk of blocks for this SuperString.



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# File 'lib/oneliner/superstring.rb', line 40

def encode(requested_size)
  raise "requested size is too small for metadata (8 bytes)" unless requested_size > 7

  ensure_encode_format
  srand
  seed = rand(Context::INT_MAX)
  context = Context.new
  context.seed(seed)
  
  rval = [self.size].pack("i")
  rval << [seed].pack("i")

  blocks = []
  wanted_blocks = ((requested_size - 8) * 8) / @block_size
  1.upto(wanted_blocks) do |n|
    blocks << generate_check_block(context, n - 1)
  end

  return rval + compact(blocks)
end