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From: Phillip Wood <phillip.wood@talktalk.net>
To: Alban Gruin <alban.gruin@gmail.com>,
	phillip.wood@dunelm.org.uk, git@vger.kernel.org
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v2 06/16] sequencer: refactor sequencer_add_exec_commands() to work on a todo_list
Date: Fri, 2 Nov 2018 10:09:52 +0000
Message-ID: <351e3398-8239-5348-2880-d253d8a125d7@talktalk.net> (raw)
In-Reply-To: <c57384de-0996-2294-db8f-0204f9c16226@gmail.com>

Hi Alban

On 01/11/2018 23:31, Alban Gruin wrote:
> Le 30/10/2018 à 17:47, Phillip Wood a écrit :
>> On 27/10/2018 22:29, Alban Gruin wrote:
>>> This refactors sequencer_add_exec_commands() to work on a todo_list to
>>> avoid redundant reads and writes to the disk.
>>>
>>> An obvious way to do this would be to insert the `exec' command between
>>> the other commands, and reparse it once this is done.  This is not what
>>> is done here.  Instead, the command is appended to the buffer once, and
>>> a new list of items is created.  Items from the old list are copied to
>>> it, and new `exec' items are appended when necessary.  This eliminates
>>> the need to reparse the todo list, but this also means its buffer cannot
>>> be directly written to the disk, hence todo_list_write_to_disk().
>>
>> I'd reword this slightly, maybe
>>
>> Instead of just inserting the `exec' command between the other commands,
>> and re-parsing the buffer at the end the exec command is appended to the
>> buffer once, and a new list of items is created.  Items from the old
>> list are copied across and new `exec' items are appended when necessary.
>>  This eliminates the need to reparse the buffer, but this also means we
>> have to use todo_list_write_to_disk() to write the file.
>>
>>> sequencer_add_exec_commands() still reads the todo list from the disk,
>>> as it is needed by rebase -p.  todo_list_add_exec_commands() works on a
>>> todo_list structure, and reparses it at the end.
>>
>> I think the saying 'reparses' is confusing as that is what we're trying
>> to avoid.
>>
>>> complete_action() still uses sequencer_add_exec_commands() for now.
>>> This will be changed in a future commit.
>>>
>>> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
>>> ---
>>>   sequencer.c | 69 +++++++++++++++++++++++++++++++++++++----------------
>>>   1 file changed, 49 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/sequencer.c b/sequencer.c
>>> index e12860c047..12a3efeca8 100644
>>> --- a/sequencer.c
>>> +++ b/sequencer.c
>>> @@ -4216,6 +4216,50 @@ int sequencer_make_script(FILE *out, int argc,
>>> const char **argv,
>>>       return 0;
>>>   }
>>>   +static void todo_list_add_exec_commands(struct todo_list *todo_list,
>>> +                    const char *commands)
>>> +{
>>> +    struct strbuf *buf = &todo_list->buf;
>>> +    const char *old_buf = buf->buf;
>>> +    size_t commands_len = strlen(commands + strlen("exec ")) - 1;
>>> +    int i, first = 1, nr = 0, alloc = 0;
>>
>> Minor nit pick, I think it is clearer if first is initialized just
>> before the loop as it is in the deleted code below.
>>
>>> +    struct todo_item *items = NULL,
>>> +        base_item = {TODO_EXEC, NULL, 0, 0, commands_len, 0};
>>> +
>>> +    strbuf_addstr(buf, commands);
>>> +    base_item.offset_in_buf = buf->len - commands_len - 1;
>>> +    base_item.arg = buf->buf + base_item.offset_in_buf;
>>
>> I think if the user gives --exec more than once on the command line then
>> commands will contain more than one exec command so this needs to parse
>> commands and create one todo_item for each command.
>>
> 
> Ouch, you’re right.  Thanks for the heads up.

I haven't looked how difficult it would be but it might be best to
change the option parsing to pass an array of strings containing the
exec commands rather than one long string so we can just loop over the
array here.

> 
>>> +
>>> +    /*
>>> +     * Insert <commands> after every pick. Here, fixup/squash chains
>>> +     * are considered part of the pick, so we insert the commands
>>> *after*
>>> +     * those chains if there are any.
>>> +     */
>>> +    for (i = 0; i < todo_list->nr; i++) {
>>> +        enum todo_command command = todo_list->items[i].command;
>>> +        if (todo_list->items[i].arg)
>>> +            todo_list->items[i].arg = todo_list->items[i].arg -
>>> old_buf + buf->buf;
>>> +
>>> +        if (command == TODO_PICK && !first) {
>>> +            ALLOC_GROW(items, nr + 1, alloc);
>>> +            memcpy(items + nr++, &base_item, sizeof(struct todo_item));
>>
>> I think it would be clearer to say
>>     items[nr++] = base_item;
>> rather than using memcpy. This applies below and to some of the other
>> patches as well. Also this needs to loop over all the base_items if the
>> user gave --exec more than once on the command line.
>>
> 
> I agree with you, it’s way more readable, IMO.  But for some reason, I
> thought it was not possible to assign a struct to another in C.

In general one needs to be careful as it is only does a shallow copy but
that is exactly what we want here. Having said that if we have an array
of exec commands to insert then it might be worth sticking with memcpy()
here so the whole array can be copied in one go.

Best Wishes

Phillip

>> Best Wishes
>>
>> Phillip
>>
> 
> Cheers,
> Alban
> 


  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-07 19:54 [PATCH 00/15] sequencer: refactor functions working " Alban Gruin
2018-10-07 19:54 ` [PATCH 01/15] sequencer: clear the number of items of a todo_list before parsing Alban Gruin
2018-10-07 19:54 ` [PATCH 02/15] sequencer: make the todo_list structure public Alban Gruin
2018-10-07 19:54 ` [PATCH 03/15] sequencer: refactor check_todo_list() to work on a todo_list Alban Gruin
2018-10-11 11:23   ` Phillip Wood
2018-10-07 19:54 ` [PATCH 04/15] sequencer: refactor sequencer_add_exec_commands() " Alban Gruin
2018-10-11 11:25   ` Phillip Wood
2018-10-11 16:57     ` Alban Gruin
2018-10-12  9:54       ` Phillip Wood
2018-10-12 12:23         ` Alban Gruin
2018-10-07 19:54 ` [PATCH 05/15] sequencer: refactor rearrange_squash() " Alban Gruin
2018-10-07 19:54 ` [PATCH 06/15] sequencer: refactor transform_todos() " Alban Gruin
2018-10-07 19:54 ` [PATCH 07/15] sequencer: make sequencer_make_script() write its script to a strbuf Alban Gruin
2018-10-12 10:01   ` SZEDER Gábor
2018-10-19  8:16     ` Junio C Hamano
2018-10-19  9:27       ` SZEDER Gábor
2018-10-07 19:54 ` [PATCH 08/15] sequencer: change complete_action() to use the refactored functions Alban Gruin
2018-10-11 13:51   ` Phillip Wood
2018-10-11 17:06     ` Alban Gruin
2018-10-07 19:54 ` [PATCH 09/15] sequencer: refactor skip_unnecessary_picks() to work on a todo_list Alban Gruin
2018-10-07 19:54 ` [PATCH 10/15] rebase-interactive: use todo_list_transform() in edit_todo_list() Alban Gruin
2018-10-11 15:16   ` Phillip Wood
2018-10-11 19:58     ` Alban Gruin
2018-10-07 19:54 ` [PATCH 11/15] rebase-interactive: append_todo_help() changes Alban Gruin
2018-10-07 19:54 ` [PATCH 12/15] rebase-interactive: rewrite edit_todo_list() to handle the initial edit Alban Gruin
2018-10-07 19:54 ` [PATCH 13/15] sequencer: use edit_todo_list() in complete_action() Alban Gruin
2018-10-07 19:54 ` [PATCH 14/15] sequencer: fix a call to error() in transform_todo_file() Alban Gruin
2018-10-07 19:54 ` [PATCH 15/15] rebase--interactive: move transform_todo_file() to rebase--interactive.c Alban Gruin
2018-10-07 20:51 ` [PATCH 00/15] sequencer: refactor functions working on a todo_list Alban Gruin
2018-10-27 21:29 ` [PATCH v2 00/16] " Alban Gruin
2018-10-27 21:29   ` [PATCH v2 01/16] sequencer: changes in parse_insn_buffer() Alban Gruin
2018-10-27 21:29   ` [PATCH v2 02/16] sequencer: make the todo_list structure public Alban Gruin
2018-10-27 21:29   ` [PATCH v2 03/16] sequencer: refactor transform_todos() to work on a todo_list Alban Gruin
2018-10-27 21:29   ` [PATCH v2 04/16] sequencer: introduce todo_list_write_to_file() Alban Gruin
2018-10-30 16:28     ` Phillip Wood
2018-11-01 23:31       ` Alban Gruin
2018-10-27 21:29   ` [PATCH v2 05/16] sequencer: refactor check_todo_list() to work on a todo_list Alban Gruin
2018-10-27 21:29   ` [PATCH v2 06/16] sequencer: refactor sequencer_add_exec_commands() " Alban Gruin
2018-10-30 16:47     ` Phillip Wood
2018-11-01 23:31       ` Alban Gruin
2018-11-02 10:09         ` Phillip Wood [this message]
2018-11-02 16:26           ` Alban Gruin
2018-11-02 17:09             ` Phillip Wood
2018-10-27 21:29   ` [PATCH v2 07/16] sequencer: refactor rearrange_squash() " Alban Gruin
2018-10-27 21:29   ` [PATCH v2 08/16] sequencer: make sequencer_make_script() write its script to a strbuf Alban Gruin
2018-10-27 21:29   ` [PATCH v2 09/16] sequencer: change complete_action() to use the refactored functions Alban Gruin
2018-10-27 21:29   ` [PATCH v2 10/16] sequencer: refactor skip_unnecessary_picks() to work on a todo_list Alban Gruin
2018-10-27 21:29   ` [PATCH v2 11/16] rebase-interactive: use todo_list_write_to_file() in edit_todo_list() Alban Gruin
2018-10-27 21:29   ` [PATCH v2 12/16] rebase-interactive: append_todo_help() changes Alban Gruin
2018-10-27 21:29   ` [PATCH v2 13/16] rebase-interactive: rewrite edit_todo_list() to handle the initial edit Alban Gruin
2018-10-27 21:29   ` [PATCH v2 14/16] sequencer: use edit_todo_list() in complete_action() Alban Gruin
2018-10-27 21:29   ` [PATCH v2 15/16] sequencer: fix a call to error() in transform_todo_file() Alban Gruin
2018-10-27 21:29   ` [PATCH v2 16/16] rebase--interactive: move transform_todo_file() to rebase--interactive.c Alban Gruin
2018-10-29  3:05   ` [PATCH v2 00/16] sequencer: refactor functions working on a todo_list Junio C Hamano
2018-10-29 15:34     ` Alban Gruin
2018-11-09  8:07   ` [PATCH v3 " Alban Gruin
2018-11-09  8:07     ` [PATCH v3 01/16] sequencer: changes in parse_insn_buffer() Alban Gruin
2018-11-09  8:07     ` [PATCH v3 02/16] sequencer: make the todo_list structure public Alban Gruin
2018-11-09  8:07     ` [PATCH v3 03/16] sequencer: refactor transform_todos() to work on a todo_list Alban Gruin
2018-11-09  8:07     ` [PATCH v3 04/16] sequencer: introduce todo_list_write_to_file() Alban Gruin
2018-11-09  8:07     ` [PATCH v3 05/16] sequencer: refactor check_todo_list() to work on a todo_list Alban Gruin
2018-11-09  8:07     ` [PATCH v3 06/16] sequencer: refactor sequencer_add_exec_commands() " Alban Gruin
2018-11-09  8:07     ` [PATCH v3 07/16] sequencer: refactor rearrange_squash() " Alban Gruin
2018-11-09  8:07     ` [PATCH v3 08/16] sequencer: make sequencer_make_script() write its script to a strbuf Alban Gruin
2018-11-09  8:07     ` [PATCH v3 09/16] sequencer: change complete_action() to use the refactored functions Alban Gruin
2018-11-09  8:07     ` [PATCH v3 10/16] sequencer: refactor skip_unnecessary_picks() to work on a todo_list Alban Gruin
2018-11-09  8:08     ` [PATCH v3 11/16] rebase-interactive: use todo_list_write_to_file() in edit_todo_list() Alban Gruin
2018-11-09  8:08     ` [PATCH v3 12/16] rebase-interactive: append_todo_help() changes Alban Gruin
2018-11-09  8:08     ` [PATCH v3 13/16] rebase-interactive: rewrite edit_todo_list() to handle the initial edit Alban Gruin
2018-11-09  8:08     ` [PATCH v3 14/16] sequencer: use edit_todo_list() in complete_action() Alban Gruin
2018-11-09  8:08     ` [PATCH v3 15/16] sequencer: fix a call to error() in transform_todo_file() Alban Gruin
2018-11-09  8:08     ` [PATCH v3 16/16] rebase--interactive: move transform_todo_file() to rebase--interactive.c Alban Gruin

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