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Re: [PATCH 1/1] Improve progress display in kB range.

From
James Cloos <cloos@jhcloos.com>
Date
Apr 22, 2009, 22:35 UTC
Message-ID
<m3ab68mi3q.fsf@lugabout.jhcloos.org>
In-Reply-To
<7vljps324a.fsf@gitster.siamese.dyndns.org>
>>>>> "Junio" == Junio C Hamano <gitster@pobox.com> writes:

Junio> If input_buffer[ret] _were_ the last octet read, [the] loop would Junio> be discarding that octet when [it] call[s] more than one xread() Junio> to fill the buffer.

That did sem more likely, but I thought I'd throw out the possibility.
I just tried instrumenting fill().

In the first call to fill() during a fetch, xread() returns 4096. In the second call to fill(), xread() returns 4095. In all subsequent calls to fill(), xread() returns 4096 again.

So, after the second call to xread(), consumed_bytes & 0xFFF == 0xFFF.
It always follows the pattern:

xread() read 0x1000 from fd 0 at 0x80a0900 ret = 0x1000 consumed_bytes = 0 input_len = 0x1000

xread() read 0xFFF from fd 0 at 0x80a0900 ret = 0xFFF consumed_bytes = 0x1000 input_len = 0xFFF

xread() read 0x1000 from fd 0 at 0x80a0900 ret = 0x1000 consumed_bytes = 0x1FFF input_len = 0x1000

with all subsequent calls reading 0x1000 and adding 0x1000 to consumed_bytes, until the final chuck of tha pack is read.

Also, all calls to xread() where the status lines are being sent from the remote server also return 0x1000 octets. Only the second chunck of a pack ever returns 0xFFF.

I've tested against a number of remote servers and the pattern holds for a wide range of remote server versions.

The pattern also holds for clones over ssh.

Does anyone have an idea of why the second call to read(2), when receiving a pack from a remote, always leaves the last octet of the buffer free, whereas all other read(2)s fill it?

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6
Previous: Junio C HamanoNext: Johannes Sixt
Message 9 of 13 in “Improve progress display in kB range.”
  1. 0/1 Improve progress display in kB range.James Cloos, Apr 19, 2009
  2. 1/1 Improve progress display in kB range.James Cloos, Apr 19, 2009
  3. Nicolas PitreApr 21, 2009
  4. James CloosApr 21, 2009
  5. Nicolas PitreApr 21, 2009
  6. James CloosApr 21, 2009
  7. James CloosApr 22, 2009
  8. Junio C HamanoApr 22, 2009
  9. James CloosApr 22, 2009
  10. Johannes SixtApr 23, 2009
  11. James CloosApr 24, 2009
  12. Nicolas PitreApr 24, 2009
  13. James CloosApr 24, 2009

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