prelude: |
  str1 = [*"A".."Z",*"0".."9"].join("")
  str10 = str1 * 10
  str100 = str10 * 10
  str1000 = str100 * 10
  nonascii1 = [*"\u{c0}".."\u{df}"].join("")
  nonascii10 = nonascii1 * 10
  nonascii100 = nonascii10 * 10
  nonascii1000 = nonascii100 * 10
  ascii8bit256 = (0..255).to_a.pack("C*")
  ascii8bit2560 = ascii8bit256 * 10
  ascii8bit25600 = ascii8bit2560 * 10
  ascii8bit256000 = ascii8bit25600 * 10
benchmark:
  downcase-1: str1.upcase
  downcase-10: str10.upcase
  downcase-100: str100.upcase
  downcase-1000: str1000.upcase
  downcase-nonascii1: nonascii1.downcase
  downcase-nonascii10: nonascii10.downcase
  downcase-nonascii100: nonascii100.downcase
  downcase-nonascii1000: nonascii1000.downcase
  downcase-ascii8bit-256: ascii8bit256.downcase
  downcase-ascii8bit-2560: ascii8bit2560.downcase
  downcase-ascii8bit-25600: ascii8bit25600.downcase
  downcase-ascii8bit-256000: ascii8bit256000.downcase