bm.rb

require 'benchmark/ips'
require 'set'
require 'digest'

# The encouragement:
# https://github.com/elia/sprockets/blob/3-0/let-it-go/lib/sprockets/digest_utils.rb#L37-L44

def digest_class
  Digest::SHA256
end

def frozen_digest(obj)
  digest = digest_class.new
  queue  = [obj]

  while queue.length > 0
    obj = queue.shift
    klass = obj.class

    if klass == String
      digest << obj
    elsif klass == Symbol
      digest << 'Symbol'.freeze
      digest << obj.to_s
    elsif klass == Fixnum
      digest << 'Fixnum'.freeze
      digest << obj.to_s
    elsif klass == Bignum
      digest << 'Bignum'.freeze
      digest << obj.to_s
    elsif klass == TrueClass
      digest << 'TrueClass'.freeze
    elsif klass == FalseClass
      digest << 'FalseClass'.freeze
    elsif klass == NilClass
      digest << 'NilClass'.freeze
    elsif klass == Array
      digest << 'Array'.freeze
      queue.concat(obj)
    elsif klass == Hash
      digest << 'Hash'.freeze
      queue.concat(obj.sort)
    elsif klass == Set
      digest << 'Set'.freeze
      queue.concat(obj.to_a)
    elsif klass == Encoding
      digest << 'Encoding'.freeze
      digest << obj.name
    else
      raise TypeError, "couldn't digest #{klass}"
    end
  end

  digest.digest
end

def digest(obj)
  digest = digest_class.new
  queue  = [obj]

  while queue.length > 0
    obj = queue.shift
    klass = obj.class

    if klass == String
      digest << obj
    elsif klass == Symbol
      digest << 'Symbol'
      digest << obj.to_s
    elsif klass == Fixnum
      digest << 'Fixnum'
      digest << obj.to_s
    elsif klass == Bignum
      digest << 'Bignum'
      digest << obj.to_s
    elsif klass == TrueClass
      digest << 'TrueClass'
    elsif klass == FalseClass
      digest << 'FalseClass'
    elsif klass == NilClass
      digest << 'NilClass'
    elsif klass == Array
      digest << 'Array'
      queue.concat(obj)
    elsif klass == Hash
      digest << 'Hash'
      queue.concat(obj.sort)
    elsif klass == Set
      digest << 'Set'
      queue.concat(obj.to_a)
    elsif klass == Encoding
      digest << 'Encoding'
      digest << obj.name
    else
      raise TypeError, "couldn't digest #{klass}"
    end
  end

  digest.digest
end

GC.disable

Benchmark.ips do |x|
  x.config(time: 5, warmup: 2)
  
  objects = [
    'asdfasd',
    nil,
    123,
    2983746198476219876492, #Bignum
    {a: 123},
    [123, 123, 123],
    Set.new([345,345,345]),
    true,
    false,
    :asdfasdf,
    "asdfasdfa".encoding,
  ]
  x.report('frozen') { objects.each {|o| frozen_digest(o)} }
  x.report('plain') { objects.each {|o| digest(o)} }

  objects = [nil]*10
  x.report('nil-frozen') { objects.each {|o| frozen_digest(o)} }
  x.report('nil-plain') { objects.each {|o| digest(o)} }
  
  x.compare!
end