Re: [PATCHv3 03/13] xread_nonblock: add functionality to read from fds nonblockingly

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 22, 2015, 00:10 UTC
Message-ID: <xmqqsi6771r2.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <1442875159-13027-4-git-send-email-sbeller@google.com>

Stefan Beller <sbeller@google.com> writes:

> This wrapper just restarts on EINTR, but not on EAGAIN like xread
> does. This gives less guarantees on the actual reading rather than
> on returning fast.

The last sentence is a bit hard to parse, by the way.

It lets caller make some progress without stalling by marking the file descriptor as nonblocking and calling this function, compared to calling xread() which will not give control back until reading the asked size (or EOF).

It is not like "reading in full is always the desireable thing to do, and returning early is something that needs compromise on that desirable behaviour to achieve", which was the way I read your version. These two kinds of callers want two different things, but the phrase "less guarantees" conveys a misguided value judgement (in that "wanting to read in full always trumps other considerations" is the stance the person who is making the judgement makes) more than useful information (e.g. "the caller may want the control back without stalling, in which case this is a useful thing to use").

The implementation itself is exactly like we discussed, and looks good.

Thanks.