gistfile1.rb

# Stream wrapper that read's IOs in succession. Can be fed to Net::HTTP. We use it to send a mixture of StringIOs
# and File handles to Net::HTTP which will be used when sending the request, not when composing it. Will skip over
# depleted IOs. Can be also used to roll across files like so:
#
#   tape = TapeIO.new(File.open(__FILE__), File.open('/etc/passwd'))
class TapeIO
  attr_accessor :substreams
  attr_accessor :release_after_use
  
  def initialize(*any_ios)
    @pending = *any_ios.flatten
  end
  
  def read(buffer_size = 1024)
    # Read off the first element in the stack
    current_io = @pending.shift
    return false if !current_io
    
    buf = current_io.read(buffer_size)
    if !buf && @pending.empty? # End of streams
      release_handle(current_io)
      false
    elsif !buf # This IO is depleted, but next one is available
      release_handle(current_io)
      read(buffer_size)
    elsif buf.length < buffer_size # This IO is depleted, but there might be more
      release_handle(current_io)
      buf + (read(buffer_size - buf.length) || '') # and recurse
    else # just return the buffer
      @pending.unshift(current_io) # put the current back
      buf
    end
  end
  
  private
    def release_handle(io)
      return unless @release_after_use
      io.close if io.respond_to?(:close)
    end
end

require 'stringio'
string_ios = ["this", "", " is", " very", "", "", " interesting"].map{|e| StringIO.new(e) }
stream = TapeIO.new(string_ios, File.open(__FILE__, 'r'))

puts stream.read(256898)
puts stream.read(256898)