instance method compute_checksum

# File activestorage/lib/active_storage/service.rb, line 156
    def compute_checksum(io, **options)
      raise ArgumentError, "io must be rewindable" unless io.respond_to?(:rewind)

      # Defer to Digest class's file implementation if File or base64digest if no chunk_size
      return checksum_implementation(**options).file(io).base64digest if io.is_a?(File)
      return checksum_implementation(**options).base64digest(io.read) if default_chunk_size.to_i == 0

      checksum_implementation(**options).new.tap do |checksum|
        read_buffer = "".b
        while io.read(default_chunk_size, read_buffer)
          checksum << read_buffer
        end

        io.rewind
      end.base64digest
    end