test.cr

require "benchmark"
require "uuid"

Benchmark.ips do |x|
  x.report { UUID.random }
end

test2.cr

require "benchmark"
require "uuid"
require "random"
module Crystal::System::Random
  GENERATOR = SecureGenerator.new

  private class SecureGenerator
    getter buffer : Bytes = Bytes.new(8192).tap { |b| Crystal::System::Random.sys_getrandom b }
    getter index = 0

    def bytes(bytes : Bytes) : Nil
      if (offset = bytes.bytesize - (buffer.bytesize - index)) > 0
        (buffer + index).copy_to bytes
        @index = 0
        Crystal::System::Random.sys_getrandom buffer
        bytes(bytes + offset)
      else
        (buffer + index).copy_to bytes.to_unsafe, bytes.bytesize
        @index += bytes.bytesize
      end
    end
  end
end

Benchmark.ips do |x|
  x.report { UUID.random }
end

test3.cr

require "benchmark"
require "uuid"
require "random"
module Crystal::System::Random
  GENERATOR = SecureGenerator.new

  private class SecureGenerator
    getter buffer : Bytes = Bytes.new(8192).tap { |b| Crystal::System::Random.sys_getrandom b }
    getter index = 0

    def bytes(bytes : Bytes) : Nil
      if (offset = bytes.bytesize - (buffer.bytesize - index)) > 0
        (buffer + index).copy_to bytes
        @index = 0
        Crystal::System::Random.sys_getrandom buffer
        bytes(bytes + offset)
      else
        (buffer + index).copy_to bytes.to_unsafe, bytes.bytesize
        @index += bytes.bytesize
      end
    end
  end
end

Benchmark.ips do |x|
m = Mutex.new
  x.report { m.synchronize {UUID.random }}
end