class Chef::Knife::Core::CookbookSiteStreamingUploader::MultipartStream

def initialize(parts)
  @parts = parts
  @part_no = 0
  @part_offset = 0
end

def read(how_much, dst_buf = nil)
  if @part_no >= @parts.size
    dst_buf.replace("") if dst_buf
    return dst_buf
  end
  how_much_current_part = @parts[@part_no].size - @part_offset
  how_much_current_part = if how_much_current_part > how_much
                            how_much
                          else
                            how_much_current_part
                          end
  how_much_next_part = how_much - how_much_current_part
  current_part = @parts[@part_no].read(@part_offset, how_much_current_part)
  # recurse into the next part if the current one was not large enough

  if how_much_next_part > 0
    @part_no += 1
    @part_offset = 0
    next_part = read(how_much_next_part)
    result = current_part + (next_part || "")
  else
    @part_offset += how_much_current_part
    result = current_part
  end
  dst_buf ? dst_buf.replace(result || "") : result
end

def size
  @parts.inject(0) { |size, part| size + part.size }
end