linux-kernel - Re: PROPOSAL: extend pipe() to support NULL argument.

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Message-ID: <4A5199F8.2010809@free.fr>
Date:	Mon, 06 Jul 2009 08:30:16 +0200
From:	Albert ARIBAUD <albert.aribaud@...e.fr>
To:	Changli Gao <xiaosuo@...il.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: PROPOSAL: extend pipe() to support NULL argument.

Changli Gao a écrit :
> On Mon, Jul 6, 2009 at 2:15 PM, Albert ARIBAUD<albert.aribaud@...e.fr> wrote:
>>>
>>> pipe doesn't support llseek.
>> I wasn't thinking of actively seeking a file position, but simply that reads
>> and writes were independent (and both variable) in size, thus even without
>> (l)seeking, each endpoint has an independent read (resp. write) position to
>> track what's been read from (resp.written into) it at any time, and such a
>> position is, IIUC, single for a given fd, making a fd (a struct file)
>> insufficient for representing a pipe.
>>
>> Amicalement,
>> --
>> Albert.
>>
> pipe doesn't refer to pos when reading or writing. Please refer to
> pipe_read() and pipe_write() for more detail.

Hmm. Then how does pipe avoid overwriting what it's already written at the 
in endpoint, or reading twice the same data from the out endpoint?

Amicalement,
-- 
Albert.
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