Re: Using to_io with Marshall.dump

[Eric Wong <normalperson@yhbt.net>]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> Hi, Ruby Marshal.dump allows writing directly into a IO object:
> 
>   dump( obj [, anIO] , limit=--1 ) → anIO
>     Serializes obj and all descendant objects. If anIO is specified, the
>     serialized data will be written to it, otherwise the data will be returned
>     as a String.
> 
> However it doesn't work with POSIX_MQ#to_io:
> 
>   Marshal.dump msg, posix_mq.to_io
> 
> => ERROR:  Errno::EINVAL: #<Errno::EINVAL: Invalid argument> (in `write')
> 
> Is it not possible or do I miss something?

POSIX_IO#to_io is a non-standard extension and only works for a few
platforms (Linux and FreeBSD) and was only intended for notification
mechanisms like select/poll/epoll/kqueue.  The underlying file
descriptor only accepts the mq_* system calls, and not the normal
read/write/fstat/close deal.

You can try aliasing POSIX_MQ#write to POSIX_MQ#send and just dump the
MQ object, but I think you're better of just dumping a string to it
since the marshalled message can exceed the size limit behind your back
(likewise with YAML/JSON/XML encoders).

-- 
Eric Wong