OpenSSL::Buffering#do_write

# File tmp/rubies/ruby-3.4.1/ext/openssl/lib/openssl/buffering.rb, line 353
def do_write(s)
  @wbuffer = Buffer.new unless defined? @wbuffer
  @wbuffer << s
  @wbuffer.force_encoding(Encoding::BINARY)
  @sync ||= false
  buffer_size = @wbuffer.size
  if @sync or buffer_size > BLOCK_SIZE
    nwrote = 0
    begin
      while nwrote < buffer_size do
        begin
          nwrote += syswrite(@wbuffer[nwrote, buffer_size - nwrote])
        rescue Errno::EAGAIN
          retry
        end
      end
    ensure
      @wbuffer[0, nwrote] = ""
    end
  end
end