Class: Epithet::Block58::Unrolled16

Inherits:
Block58
  • Object
show all
Defined in:
lib/epithet.rb

Overview

Specialised decoder for 16-byte blocks (22 digits) with a fully unrolled inner product.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Unrolled16

Returns a new instance of Unrolled16.

Raises:

  • (ArgumentError) 


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# File 'lib/epithet.rb', line 322

def initialize(...)
  super
  raise ArgumentError, 'unrolled codec requires a 16-byte block' unless @size == 22
end

Instance Method Details

#s2i(str) ⇒ Object

Decode a fixed-length Base58 string to an Integer. Assumes the input passes #valid?.



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# File 'lib/epithet.rb', line 329

def s2i(str)
  # rubocop:disable Style/NumericLiterals, Lint/AmbiguousOperatorPrecedence, Layout
  #
  # By unrolling the chunks against literal coefficients, this is ~1.6x
  # faster under YJIT than the generic chunked Block58#s2i, and ~8x
  # faster than Horner's scheme.
  lut = @lut

  acc0 = lut.getbyte(str.getbyte(0)) * 7427658739644928 +
         lut.getbyte(str.getbyte(1)) * 128063081718016 +
         lut.getbyte(str.getbyte(2)) * 2207984167552 +
         lut.getbyte(str.getbyte(3)) * 38068692544 +
         lut.getbyte(str.getbyte(4)) * 656356768 +
         lut.getbyte(str.getbyte(5)) * 11316496 +
         lut.getbyte(str.getbyte(6)) * 195112 +
         lut.getbyte(str.getbyte(7)) * 3364 +
         lut.getbyte(str.getbyte(8)) * 58 +
         lut.getbyte(str.getbyte(9))

  acc1 = lut.getbyte(str.getbyte(10)) * 7427658739644928 +
         lut.getbyte(str.getbyte(11)) * 128063081718016 +
         lut.getbyte(str.getbyte(12)) * 2207984167552 +
         lut.getbyte(str.getbyte(13)) * 38068692544 +
         lut.getbyte(str.getbyte(14)) * 656356768 +
         lut.getbyte(str.getbyte(15)) * 11316496 +
         lut.getbyte(str.getbyte(16)) * 195112 +
         lut.getbyte(str.getbyte(17)) * 3364 +
         lut.getbyte(str.getbyte(18)) * 58 +
         lut.getbyte(str.getbyte(19))

                           lut.getbyte(str.getbyte(21)) +
                      58 * lut.getbyte(str.getbyte(20)) +
                    3364 * acc1 +
  1449225352009601191936 * acc0

  # rubocop:enable Style/NumericLiterals, Lint/AmbiguousOperatorPrecedence, Layout
end