Method: String#truncate_bytes

Defined in:
lib/simple_ext/string/filters.rb

#truncate_bytes(truncate_at, omission: "…") ⇒ Object

Truncates text to at most bytesize bytes in length without breaking string encoding by splitting multibyte characters or breaking grapheme clusters (“perceptual characters”) by truncating at combining characters.

>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".size
=> 20
>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".bytesize
=> 80
>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".truncate_bytes(20)
=> "🔪🔪🔪🔪…"

The truncated text ends with the :omission string, defaulting to “…”, for a total length not exceeding bytesize.



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# File 'lib/simple_ext/string/filters.rb', line 95

def truncate_bytes(truncate_at, omission: "…")
  omission ||= ""

  case
  when bytesize <= truncate_at
    dup
  when omission.bytesize > truncate_at
    raise ArgumentError, "Omission #{omission.inspect} is #{omission.bytesize}, larger than the truncation length of #{truncate_at} bytes"
  when omission.bytesize == truncate_at
    omission.dup
  else
    self.class.new.tap do |cut|
      cut_at = truncate_at - omission.bytesize

      scan(/\X/) do |grapheme|
        if cut.bytesize + grapheme.bytesize <= cut_at
          cut << grapheme
        else
          break
        end
      end

      cut << omission
    end
  end
end