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Date: Fri, 29 Nov 2019 08:59:39 +0300
From: Konstantin Osipov <kostja.osipov@gmail.com>
Message-ID: <20191129055939.GH15149@atlas>
References: <20191128204512.19732-1-gorcunov@gmail.com>
 <20191128204512.19732-2-gorcunov@gmail.com>
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In-Reply-To: <20191128204512.19732-2-gorcunov@gmail.com>
Subject: Re: [Tarantool-patches] [PATCH 1/5] popen: Introduce a backend
	engine
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To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: tml <tarantool-patches@dev.tarantool.org>

* Cyrill Gorcunov <gorcunov@gmail.com> [19/11/28 23:46]:
> +/**
> + * popen_write - write data to the child stdin
> + * @handle:	popen handle
> + * @buf:	data to write
> + * @count:	number of bytes to write
> + * @flags:	a flag representing stdin peer
> + *
> + * Returns number of bytes written or -1 on error.
> + */
> +ssize_t
> +popen_write(struct popen_handle *handle, void *buf,
> +	    size_t count, unsigned int flags)
> +{
> +	if (!popen_may_io(handle, STDIN_FILENO, flags))
> +		return -1;
> +
> +	say_debug("popen: %d: write idx %d",
> +		  handle->pid, STDIN_FILENO);
> +
> +	return write(handle->fds[STDIN_FILENO], buf, count);

I don't understand, is this blocking or not?

If this is blocking, where is it supposed to be called from?

Shouldn't you be using a non-blocking I/O like coio does?

Besides, even though I realize it's a pipe, so real world
return values may be different, but write() can return a partial
result even in blocking mode. Why did you choose to design an API
which will require caller to handle partial writes?


-- 
Konstantin Osipov, Moscow, Russia