String::Chars

string_with_chars.cr

class String
  struct Chars
    include Indexable(Char)

    def initialize(@str : String)
    end

    def unsafe_fetch(index)
      @str.char_at(index)
    end

    def each
      if @str.ascii_only?
        @str.each_byte do |byte|
          yield (byte < 0x80 ? byte.unsafe_chr : Char::REPLACEMENT)
        end
      else
        Char::Reader.new(@str).each do |char|
          yield char
        end
      end
    end
  end

  def chars2
    Chars.new self
  end
end

require "benchmark"

STR = "string"
STR999 = STR * 999

Benchmark.ips do |x|
  x.report("String#chars.map") do
    STR.chars.map { |c| }
  end

  x.report("String#each_char.to_a.map") do
    STR.each_char.to_a.map { |c| }
  end

  x.report("String#chars2.map") do
    STR.chars2.map { |c| }                                               
  end                    
end


Benchmark.ips do |x|
  x.report("Big String#chars.map") do
    STR999.chars.map { |c| }
  end

  x.report("Big String#each_char.to_a.map") do
    STR999.each_char.to_a.map { |c| }
  end

  x.report("Big String#chars2.map") do
    STR999.chars2.map { |c| }                                               
  end                    
end

<<-RESULT
         String#chars.map   9.16M (109.16ns) (± 9.44%)  112 B/op   2.31× slower
String#each_char.to_a.map   3.97M ( 251.8ns) (±15.06%)  209 B/op   5.32× slower
        String#chars2.map  21.14M ( 47.31ns) (± 6.35%)   48 B/op        fastest
         Big String#chars.map  19.02k ( 52.58µs) (±30.32%)  24064 B/op  10.34× slower
Big String#each_char.to_a.map  16.69k ( 59.92µs) (±21.55%)  50032 B/op  11.78× slower
        Big String#chars2.map 196.65k (  5.09µs) (± 7.66%)    128 B/op        fastest
RESULT