Re: [boost] [Interprocess] Named pipe interface proposal

Subject: Re: [boost] [Interprocess] Named pipe interface proposal
From: Boris Schaeling (boris_at_[hidden])
Date: 2013-08-11 08:11:58

On Sat, 10 Aug 2013 03:45:38 +0200, Geoff Shannon  
<geoffpshannon_at_[hidden]> wrote:

Hi Geoff,

> [...]As a point of interest this interface is meant to be extremely  
> simple.  I
> don't intend to initially support ANYTHING except for basic creation and
> reading and writing.

I'm interested in named pipe support as Boost.Process could benefit a lot  
(not an official Boost library but everyone calls it like that).

We have a function called create_pipe() which creates an anonymous pipe  
(see  
<http://www.highscore.de/boost/process0.5/boost/process/create_pipe_id341354.html>).  
The function returns an object which is similar to a pair of file  
descriptors/Windows handles (see  
<http://www.highscore.de/boost/process0.5/boost/process/pipe.html>). The  
library refers to these things as pipe ends. The pipe ends can be used to  
create a boost::iostreams::file_descriptor_source or  
boost::iostreams::file_descriptor_sink object to do synchronous I/O (see  
<http://www.highscore.de/boost/process0.5/boost_process/tutorial.html#boost_process.tutorial.synchronous_i_o>).

For asynchronous I/O Windows requires a named pipe. Boost.Process doesn't  
provide anything out of the box to help users though. There is a  
create_async_pipe() function used in the documentation. But it's left as  
an exercise to the reader to implement it. :/ I actually implemented it in  
the unit tests. But there is too much hardcoded that it's of any use to  
others.

This function create_async_pipe() returns the same pair of file  
descriptors/Windows handles as create_pipe() does. Instead of putting  
these pipe ends into Boost.Iostreams objects they are now used to  
instantiate boost::asio::windows::stream_handle or  
boost::asio::posix::stream_descriptor (see  
<http://www.highscore.de/boost/process0.5/boost_process/tutorial.html#boost_process.tutorial.asynchronous_i_o>).  
These classes from Boost.Asio can be used as is for asynchronous I/O with  
named pipes.

All of that is really a low-level view as you actually deal with file  
descriptors/Windows handles. I don't know whether you want to go that way  
(your interface makes me think you are higher level). If you can provide a  
Boost.Asio I/O object for named pipes, or if you can provide access to the  
pipe ends of your named pipe it would however help to make asynchronous  
I/O with Boost.Process easier to use.

Boris