From: "Jakub Narębski" <jnareb@gmail.com>
To: Lars Schneider <larsxschneider@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
Junio C Hamano <gitster@pobox.com>,
tboegi@web.de, mlbright@gmail.com, Eric Wong <e@80x24.org>,
Jeff King <peff@peff.net>
Subject: Re: [PATCH v3 02/10] pkt-line: add direct_packet_write() and direct_packet_write_data()
Date: Wed, 3 Aug 2016 22:12:48 +0200 [thread overview]
Message-ID: <e8b550ed-1765-764f-49e5-72e5a609d936@gmail.com> (raw)
In-Reply-To: <64783AA5-D579-4783-88E7-E0B3BDE5FDEB@gmail.com>
[This response might have been invalidated by v4]
W dniu 01.08.2016 o 14:00, Lars Schneider pisze:
>> On 30 Jul 2016, at 12:49, Jakub Narębski <jnareb@gmail.com> wrote:
>> W dniu 30.07.2016 o 01:37, larsxschneider@gmail.com pisze:
>>>
>>> Sometimes pkt-line data is already available in a buffer and it would
>>> be a waste of resources to write the packet using packet_write() which
>>> would copy the existing buffer into a strbuf before writing it.
>>>
>>> If the caller has control over the buffer creation then the
>>> PKTLINE_DATA_START macro can be used to skip the header and write
>>> directly into the data section of a pkt-line (PKTLINE_DATA_LEN bytes
>>> would be the maximum). direct_packet_write() would take this buffer,
>>> adjust the pkt-line header and write it.
>>>
>>> If the caller has no control over the buffer creation then
>>> direct_packet_write_data() can be used. This function creates a pkt-line
>>> header. Afterwards the header and the data buffer are written using two
>>> consecutive write calls.
>>
>> I don't quite understand what do you mean by "caller has control
>> over the buffer creation". Do you mean that caller either can write
>> over the buffer, or cannot overwrite the buffer? Or do you mean that
>> caller either can allocate buffer to hold header, or is getting
>> only the data?
>
> How about this:
>
> [...]
>
> If the caller creates the buffer then a proper pkt-line buffer with header
> and data section can be created. The PKTLINE_DATA_START macro can be used
> to skip the header section and write directly to the data section (PKTLINE_DATA_LEN
> bytes would be the maximum). direct_packet_write() would take this buffer,
> fill the pkt-line header section with the appropriate data length value and
> write the entire buffer.
>
> If the caller does not create the buffer, and consequently cannot leave room
> for the pkt-line header, then direct_packet_write_data() can be used. This
> function creates an extra buffer for the pkt-line header and afterwards writes
> the header buffer and the data buffer with two consecutive write calls.
>
> ---
> Is that more clear?
Yes, I think it is more clear.
The only thing that could be improved is to perhaps instead of using
"then a proper pkt-line buffer with header and data section can be created"
it might be more clear to write
"then a proper pkt-line buffer with data section and a place for pkt-line header"
>>> +{
>>> + int ret = 0;
>>> + char hdr[4];
>>> + set_packet_header(hdr, sizeof(hdr) + size);
>>> + packet_trace(buf, size, 1);
>>> + if (gentle) {
>>> + ret = (
>>> + !write_or_whine_pipe(fd, hdr, sizeof(hdr), "pkt-line header") ||
>>
>> You can write '4' here, no need for sizeof(hdr)... though compiler would
>> optimize it away.
>
> Right, it would be optimized. However, I don't like the 4 there either. OK to use a macro
> instead? PKTLINE_HEADER_LEN ?
Did you mean
+ char hdr[PKTLINE_HEADER_LEN];
+ set_packet_header(hdr, sizeof(hdr) + size);
>>> + !write_or_whine_pipe(fd, buf, size, "pkt-line data")
>>> + );
>>
>> Do we want to try to write "pkt-line data" if "pkt-line header" failed?
>> If not, perhaps De Morgan-ize it
>>
>> + ret = !(
>> + write_or_whine_pipe(fd, hdr, sizeof(hdr), "pkt-line header") &&
>> + write_or_whine_pipe(fd, buf, size, "pkt-line data")
>> + );
>
>
> Original:
> ret = (
> !write_or_whine_pipe(fd, hdr, sizeof(hdr), "pkt-line header") ||
> !write_or_whine_pipe(fd, data, size, "pkt-line data")
> );
>
> Well, if the first write call fails (return == 0), then it is negated and evaluates to true.
> I would think the second call is not evaluated, then?!
This is true both for || and for &&, as in C logical boolean operators
short-circuit.
> Should I make this more explicit with a if clause?
No need.
--
Jakub Narębski
next prev parent reply other threads:[~2016-08-03 20:19 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20160727000605.49982-1-larsxschneider%40gmail.com/>
2016-07-29 23:37 ` [PATCH v3 00/10] Git filter protocol larsxschneider
2016-07-29 23:37 ` [PATCH v3 01/10] pkt-line: extract set_packet_header() larsxschneider
2016-07-30 10:30 ` Jakub Narębski
2016-08-01 11:33 ` Lars Schneider
2016-08-03 20:05 ` Jakub Narębski
2016-08-05 11:52 ` Lars Schneider
2016-07-29 23:37 ` [PATCH v3 02/10] pkt-line: add direct_packet_write() and direct_packet_write_data() larsxschneider
2016-07-30 10:49 ` Jakub Narębski
2016-08-01 12:00 ` Lars Schneider
2016-08-03 20:12 ` Jakub Narębski [this message]
2016-08-05 12:02 ` Lars Schneider
2016-07-29 23:37 ` [PATCH v3 03/10] pkt-line: add packet_flush_gentle() larsxschneider
2016-07-30 12:04 ` Jakub Narębski
2016-08-01 12:28 ` Lars Schneider
2016-07-31 20:36 ` Torstem Bögershausen
2016-07-31 21:45 ` Lars Schneider
2016-08-02 19:56 ` Torsten Bögershausen
2016-08-05 9:59 ` Lars Schneider
2016-07-29 23:37 ` [PATCH v3 04/10] pkt-line: call packet_trace() only if a packet is actually send larsxschneider
2016-07-30 12:29 ` Jakub Narębski
2016-08-01 12:18 ` Lars Schneider
2016-08-03 20:15 ` Jakub Narębski
2016-07-29 23:37 ` [PATCH v3 05/10] pack-protocol: fix maximum pkt-line size larsxschneider
2016-07-30 13:58 ` Jakub Narębski
2016-08-01 12:23 ` Lars Schneider
2016-07-29 23:37 ` [PATCH v3 06/10] run-command: add clean_on_exit_handler larsxschneider
2016-07-30 9:50 ` Johannes Sixt
2016-08-01 11:14 ` Lars Schneider
2016-08-02 5:53 ` Johannes Sixt
2016-08-02 7:41 ` Lars Schneider
2016-07-29 23:37 ` [PATCH v3 07/10] convert: quote filter names in error messages larsxschneider
2016-07-29 23:37 ` [PATCH v3 08/10] convert: modernize tests larsxschneider
2016-07-29 23:38 ` [PATCH v3 09/10] convert: generate large test files only once larsxschneider
2016-07-29 23:38 ` [PATCH v3 10/10] convert: add filter.<driver>.process option larsxschneider
2016-07-30 22:05 ` Jakub Narębski
2016-07-31 9:42 ` Jakub Narębski
2016-07-31 19:49 ` Lars Schneider
2016-07-31 22:59 ` Jakub Narębski
2016-08-01 13:32 ` Lars Schneider
2016-08-03 18:30 ` Designing the filter process protocol (was: Re: [PATCH v3 10/10] convert: add filter.<driver>.process option) Jakub Narębski
2016-08-05 10:32 ` Lars Schneider
2016-08-06 18:24 ` Lars Schneider
2016-08-03 22:47 ` [PATCH v3 10/10] convert: add filter.<driver>.process option Jakub Narębski
2016-07-31 22:19 ` Jakub Narębski
2016-08-01 17:55 ` Lars Schneider
2016-08-04 0:42 ` Jakub Narębski
2016-08-03 13:10 ` Lars Schneider
2016-08-04 10:18 ` Jakub Narębski
2016-08-05 13:20 ` Lars Schneider
2016-08-03 16:42 ` [PATCH v4 00/12] Git filter protocol larsxschneider
2016-08-03 16:42 ` [PATCH v4 01/12] pkt-line: extract set_packet_header() larsxschneider
2016-08-03 20:18 ` Junio C Hamano
2016-08-03 21:12 ` Jeff King
2016-08-03 21:27 ` Jeff King
2016-08-04 16:14 ` Junio C Hamano
2016-08-05 14:55 ` Lars Schneider
2016-08-05 16:31 ` Junio C Hamano
2016-08-05 17:31 ` Lars Schneider
2016-08-05 17:41 ` Junio C Hamano
2016-08-03 21:56 ` Lars Schneider
2016-08-03 16:42 ` [PATCH v4 02/12] pkt-line: add direct_packet_write() and direct_packet_write_data() larsxschneider
2016-08-03 16:42 ` [PATCH v4 03/12] pkt-line: add packet_flush_gentle() larsxschneider
2016-08-03 21:39 ` Jeff King
2016-08-03 22:56 ` [PATCH 0/7] minor trace fixes and cosmetic improvements Jeff King
2016-08-03 22:56 ` [PATCH 1/7] trace: handle NULL argument in trace_disable() Jeff King
2016-08-03 22:58 ` [PATCH 2/7] trace: stop using write_or_whine_pipe() Jeff King
2016-08-03 22:58 ` [PATCH 3/7] trace: use warning() for printing trace errors Jeff King
2016-08-04 20:41 ` Junio C Hamano
2016-08-04 21:21 ` Jeff King
2016-08-04 21:28 ` Junio C Hamano
2016-08-05 7:56 ` Jeff King
2016-08-05 7:59 ` Christian Couder
2016-08-05 18:41 ` Junio C Hamano
2016-08-03 23:00 ` [PATCH 4/7] trace: cosmetic fixes for error messages Jeff King
2016-08-04 20:42 ` Junio C Hamano
2016-08-05 8:00 ` Jeff King
2016-08-03 23:00 ` [PATCH 5/7] trace: correct variable name in write() error message Jeff King
2016-08-03 23:01 ` [PATCH 6/7] trace: disable key after write error Jeff King
2016-08-04 20:45 ` Junio C Hamano
2016-08-04 21:22 ` Jeff King
2016-08-05 7:58 ` Jeff King
2016-08-03 23:01 ` [PATCH 7/7] write_or_die: drop write_or_whine_pipe() Jeff King
2016-08-03 23:04 ` [PATCH 0/7] minor trace fixes and cosmetic improvements Jeff King
2016-08-04 16:16 ` [PATCH v4 03/12] pkt-line: add packet_flush_gentle() Junio C Hamano
2016-08-03 16:42 ` [PATCH v4 04/12] pkt-line: call packet_trace() only if a packet is actually send larsxschneider
2016-08-03 16:42 ` [PATCH v4 05/12] pkt-line: add functions to read/write flush terminated packet streams larsxschneider
2016-08-03 16:42 ` [PATCH v4 06/12] pack-protocol: fix maximum pkt-line size larsxschneider
2016-08-03 16:42 ` [PATCH v4 07/12] run-command: add clean_on_exit_handler larsxschneider
2016-08-03 21:24 ` Jeff King
2016-08-03 22:15 ` Lars Schneider
2016-08-03 22:53 ` Jeff King
2016-08-03 23:09 ` Lars Schneider
2016-08-03 23:15 ` Jeff King
2016-08-05 13:08 ` Lars Schneider
2016-08-05 21:19 ` Torsten Bögershausen
2016-08-05 21:50 ` Lars Schneider
2016-08-03 16:42 ` [PATCH v4 08/12] convert: quote filter names in error messages larsxschneider
2016-08-03 16:42 ` [PATCH v4 09/12] convert: modernize tests larsxschneider
2016-08-03 16:42 ` [PATCH v4 10/12] convert: generate large test files only once larsxschneider
2016-08-03 16:42 ` [PATCH v4 11/12] convert: add filter.<driver>.process option larsxschneider
2016-08-03 17:45 ` Junio C Hamano
2016-08-03 21:48 ` Lars Schneider
2016-08-03 22:46 ` Jeff King
2016-08-05 12:53 ` Lars Schneider
2016-08-03 20:29 ` Junio C Hamano
2016-08-03 21:37 ` Lars Schneider
2016-08-03 21:43 ` Junio C Hamano
2016-08-03 22:01 ` Lars Schneider
2016-08-05 21:34 ` Torsten Bögershausen
2016-08-05 21:49 ` Lars Schneider
2016-08-05 22:06 ` Junio C Hamano
2016-08-05 22:27 ` Jeff King
2016-08-06 11:55 ` Lars Schneider
2016-08-06 12:14 ` Jeff King
2016-08-06 18:19 ` Lars Schneider
2016-08-08 15:02 ` Jeff King
2016-08-08 16:21 ` Lars Schneider
2016-08-08 16:26 ` Jeff King
2016-08-06 20:40 ` Torsten Bögershausen
2016-08-03 16:42 ` [PATCH v4 12/12] convert: add filter.<driver>.process shutdown command option larsxschneider
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