From: brian ford <brixen@...>
Date: 2011-08-28T02:33:42+09:00
Subject: [ruby-core:39145] Re: [Ruby 1.9 - Bug #5237] IO.copy_stream calls #read on an object infinitely many times

On Sat, Aug 27, 2011 at 3:54 AM, Eric Wong <normalperson@yhbt.net> wrote:
>
> Issue #5237 has been updated by Eric Wong.
>
> File 0001-avoid-infinite-loop-of-IO.copy_stream.patch added
>
> The class that implements an IO#read-like method without clearing
> the destination buffer on EOF is arguably broken, but infinite
> looping is bad, I think.

Ah, you are right, it really should replace buffer with "" (according
to the code) and return nil according to the docs. Seems more than a
little weird, however, to empty the buffer to signal EOF, especially
since the buffer argument is optional.

Cheers,
Brian

>
> The attached simple patch should fix the issue. �Also available via git:
> �git pull git://bogomips.org/ruby.git copy-stream-infinite-loop
>
> ----------------------------------------
> Bug #5237: IO.copy_stream calls #read on an object infinitely many times
> http://redmine.ruby-lang.org/issues/5237
>
> Author: Brian Ford
> Status: Open
> Priority: Normal
> Assignee:
> Category: core
> Target version:
> ruby -v: ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
>
>
> The code for IO.copy_stream appears to support passing any object that implements #readpartial or #read. For example, passing an instance of StringIO works just fine:
>
> sasha:rubinius2.0 brian$ irb
> ruby-1.9.2-p290 :001 > puts RUBY_DESCRIPTION
> ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
> �=> nil
> ruby-1.9.2-p290 :002 > require 'stringio'
> �=> true
> ruby-1.9.2-p290 :003 > s = StringIO.new "this is a test"
> �=> #<StringIO:0x00000100851190>
> ruby-1.9.2-p290 :004 > IO.copy_stream s, "copy_stream_stringio"
> �=> 14
> ruby-1.9.2-p290 :005 > IO.read "copy_stream_stringio"
> �=> "this is a test"
> ruby-1.9.2-p290 :006 >
>
> However, passing an object that implements eg #read according to the specification of IO#read, causes IO.copy_stream to endlessly call #read on the object:
>
> class A
> �def initialize
> � �@count = 0
> �end
>
> �def read(bytes, buffer)
> � �print "read: #{@count += 1}\r"
> � �buffer.replace "this is a test"
> � �return nil
> �end
> end
>
> a = A.new
> IO.copy_stream a, "copy_stream_test"
>
> ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
> copy_stream_bug.rb:7:in `write': Interrupt
> � � � �from copy_stream_bug.rb:7:in `print'
> � � � �from copy_stream_bug.rb:7:in `read'
> � � � �from copy_stream_bug.rb:14:in `copy_stream'
> � � � �from copy_stream_bug.rb:14:in `<main>'
>
> Thanks,
> Brian
>
>
> --
> http://redmine.ruby-lang.org
>
>