#!/usr/bin/env ruby
# frozen_string_literal: true

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'benchmark-ips'
end

$LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
require 'ragel/bitmap'

numbers = Array.new(10_000) { rand(2**16) }
offsets = numbers.pack('S*')

high = numbers.map { |number| number >> 8 }.pack('C*')
low = numbers.pack('C*')

# Here we're measuring if it's faster to use unpack1 with offset or if it's
# faster to keep two separate strings around, use getbyte, and | them together
# for 16-byte unsigned integers.
Benchmark.ips do |x|
  x.report('16-byte offsets') do
    index = rand(10_000)
    offsets.unpack1('S', offset: index)
  end

  x.report('16-byte strings') do
    index = rand(10_000)
    (high.getbyte(index) << 8) | low.getbyte(index)
  end

  x.compare!
end

numbers = Array.new(10_000) { rand(2**32) }
offsets = numbers.pack('L*')
high, midhigh, midlow, low =
  [24, 16, 8, 0].map do |shift|
    numbers.map { |number| number >> shift }.pack('C*')
  end

# Here we're measuring the same difference but this time we're using 32-byte
# unsigned integers instead.
Benchmark.ips do |x|
  x.report('32-byte offsets') do
    index = rand(10_000)
    offsets.unpack1('L', offset: index)
  end

  x.report('32-byte strings') do
    index = rand(10_000)
    (high.getbyte(index) << 24) |
      (midhigh.getbyte(index) << 16) |
      (midlow.getbyte(index) << 8) |
      low.getbyte(index)
  end

  x.compare!
end

numbers = Array.new(10_000) { rand(2**64) }
offsets = numbers.pack('Q*')
highest, midhighest, high, midhigh, midlow, low, midlowest, lowest =
  [56, 48, 40, 32, 24, 16, 8, 0].map do |shift|
    numbers.map { |number| number >> shift }.pack('C*')
  end

# Here we're measuring the same difference but this time we're using 64-byte
# unsigned integers instead.
Benchmark.ips do |x|
  x.report('64-byte offsets') do
    index = rand(10_000)
    offsets.unpack1('Q', offset: index)
  end

  x.report('64-byte strings') do
    index = rand(10_000)

    (highest.getbyte(index) << 56) |
      (midhighest.getbyte(index) << 48) |
      (high.getbyte(index) << 40) |
      (midhigh.getbyte(index) << 32) |
      (midlow.getbyte(index) << 24) |
      (low.getbyte(index) << 16) |
      (midlowest.getbyte(index) << 8) |
      lowest.getbyte(index)
  end

  x.compare!
end