Increase speed of UUID generation

[robotblake]

This change speeds up UUID generation by somewhere between 10-40%. Originally implemented as part of https://github.com/robotblake/hakusho.

Benchmark Methodology

• First install the benchmark-ips gem and then create a file called benchmark.rb in the root of the repo with the following content.

  require "benchmark/ips"
  
  lib = File.expand_path("../lib", __FILE__)
  $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
  require "securerandom"
  
  Benchmark.ips do |x|
    x.report(`git rev-parse --short HEAD`.strip) do
      SecureRandom.uuid
    end
    x.save! "uuid.out"
    x.compare!
  end

• Checkout the v0.2.0 tag, and run ruby benchmark.rb.

• Checkout the b587b8c commit, and run ruby benchmark.rb.

Benchmark Results

~/Projects/securerandom ❯ git checkout v0.2.0
HEAD is now at 62ca282 Bump up v0.2.0

~/Projects/securerandom ❯ ruby benchmark.rb 
Warming up --------------------------------------
             62ca282    93.716k i/100ms
Calculating -------------------------------------
             62ca282    941.790k (± 0.3%) i/s -      4.780M in   5.074975s

~/Projects/securerandom ❯ git checkout b587b8c
Previous HEAD position was 62ca282 Bump up v0.2.0
HEAD is now at b587b8c Increase speed of UUID generation

~/Projects/securerandom ❯ ruby benchmark.rb
Warming up --------------------------------------
             b587b8c   131.060k i/100ms
Calculating -------------------------------------
             b587b8c      1.312M (± 0.4%) i/s -      6.684M in   5.093688s

Comparison:
             b587b8c:  1312244.3 i/s
             62ca282:   941790.2 i/s - 1.39x  (± 0.00) slower

[BenMorganMY]

@robotblake would you be able to explain how this improved the performance? As a generally curious programmer and seeing the dependabot updates on my projects, I'm sure other devs will be coming here to learn about the improvements.