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Re: [PATCH 29/30] create_dir_entry(): allow the flag value to be passed as an argument

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Apr 26, 2012, 21:12 UTC
Message-ID
<4F99BA36.5070803@alum.mit.edu>
In-Reply-To
<xmqq62cnd4pv.fsf@junio.mtv.corp.google.com>
On 04/25/2012 08:52 PM, Junio C Hamano wrote:
Show 39 quoted lines
> Junio C Hamano<gitster@pobox.com>  writes:
>
>> mhagger@alum.mit.edu writes:
>>
>>> diff --git a/refs.c b/refs.c
>>> index 4eca965..869c9a7 100644
>>> --- a/refs.c
>>> +++ b/refs.c
>>> @@ -231,18 +231,18 @@ static void clear_ref_dir(struct ref_dir *dir)
>>>   }
>>>
>>>   /*
>>> + * Create a struct ref_entry object for the specified dirname and flag.
>>>    * dirname is the name of the directory with a trailing slash (e.g.,
>>>    * "refs/heads/") or "" for the top-level directory.
>>>    */
>>>   static struct ref_entry *create_dir_entry(struct ref_cache *ref_cache,
>>> -					  const char *dirname)
>>> +					  const char *dirname, int flag)
>>>   {
>>>   	struct ref_entry *direntry;
>>>   	int len = strlen(dirname);
>>>   	direntry = xcalloc(1, sizeof(struct ref_entry) + len + 1);
>>>   	memcpy(direntry->name, dirname, len + 1);
>>> -	direntry->flag = REF_DIR;
>>> +	direntry->flag = flag;
>>>   	direntry->u.subdir.ref_cache = ref_cache;
>>
>> As the returned structure will always represent a subdirectory and not a
>> leaf node, i.e. you use u.subdir, I do not think it makes any sense to
>> make it responsibility for the caller of this function to include
>> REF_DIR in the value of the flag.
>
> Forseeing a response "But but but REF_DIR will become OR of two
> variants", my complaint is still valid ;-) and it is the bit assignment
> you did in the final patch that is wrong.  If you make REF_DIR (or not)
> to differenticate between ref_dir vs ref_value, and use another bit
> REF_INCOMPLETE to remember that you still need to find out the actual
> value of it, the the above can still be

In an earlier design, there were three types of REF_DIR: packed, loose(read), and loose(unread), which could all be packed (along with dir/non-dir) into two bits. The current bit assignment was left over from that design, plus a latent expectation that it would sometime be necessary to distinguish between packed and loose(read) references.

But so far I haven't found a reason to distinguish between packed and loose(read), so your suggested bit assignment is simpler. I will include it in the next version of the patch series.

Show 6 quoted lines
> The suggested bit assignment would also allow you to create ref_value
> leaf nodes, whose presence you know about (by iterating over readdir()
> results) but not their values yet (because you haven't opened and read
> them), by marking them with REF_INCOMPLETE to be extra lazy in the
> future, if necessary.  I do not know if that much laziness buys us a
> lot, though ;-).
This would be pretty easy to implement.  Maybe I'll try it someday.
Michael
-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/
Previous: Junio C HamanoNext: mhagger@alum.mit.edu
Message 34 of 37 in “Read loose references lazily”
  1. 00/30 Read loose references lazilymhagger@alum.mit.edu, Apr 24, 2012
  2. 01/30 get_ref_dir(): return early if directory cannot be readmhagger@alum.mit.edu, Apr 24, 2012
  3. 02/30 get_ref_dir(): use a strbuf to hold refnamemhagger@alum.mit.edu, Apr 24, 2012
  4. 03/30 get_ref_dir(): rename "base" parameter to "dirname"mhagger@alum.mit.edu, Apr 24, 2012
  5. 04/30 get_ref_dir(): require that the dirname argument ends in '/'mhagger@alum.mit.edu, Apr 24, 2012
  6. 05/30 refs.c: extract function search_for_subdir()mhagger@alum.mit.edu, Apr 24, 2012
  7. 06/30 get_ref_dir(): take the containing directory as argumentmhagger@alum.mit.edu, Apr 24, 2012
  8. 07/30 do_for_each_reflog(): return early on errormhagger@alum.mit.edu, Apr 24, 2012
  9. 08/30 do_for_each_reflog(): use a strbuf to hold logfile namemhagger@alum.mit.edu, Apr 24, 2012
  10. 09/30 do_for_each_reflog(): reuse strbuf across recursive function callsmhagger@alum.mit.edu, Apr 24, 2012
  11. 10/30 refs: wrap top-level ref_dirs in ref_entriesmhagger@alum.mit.edu, Apr 24, 2012
  12. Michael HaggertyApr 26, 2012
  13. 11/30 get_packed_refs(): return (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  14. 12/30 get_loose_refs(): return (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  15. 13/30 is_refname_available(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  16. 14/30 find_ref(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  17. 15/30 read_packed_refs(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  18. 16/30 add_ref(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  19. 17/30 find_containing_direntry(): use (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  20. 18/30 get_ref_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  21. 19/30 get_ref_dir(): remove dirname argumentmhagger@alum.mit.edu, Apr 24, 2012
  22. 20/30 search_for_subdir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  23. 21/30 search_ref_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  24. 22/30 add_entry(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  25. 23/30 do_for_each_ref_in_dirs(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  26. 24/30 do_for_each_ref_in_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  27. 25/30 sort_ref_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Apr 24, 2012
  28. 26/30 struct ref_dir: store a reference to the enclosing ref_cachemhagger@alum.mit.edu, Apr 24, 2012
  29. 27/30 read_loose_refs(): rename function from get_ref_dir()mhagger@alum.mit.edu, Apr 24, 2012
  30. 28/30 read_loose_refs(): access ref_cache via the ref_dir fieldmhagger@alum.mit.edu, Apr 24, 2012
  31. 29/30 create_dir_entry(): allow the flag value to be passed as an argumentmhagger@alum.mit.edu, Apr 24, 2012
  32. Junio C HamanoApr 25, 2012
  33. Junio C HamanoApr 25, 2012
  34. Michael HaggertyApr 26, 2012
  35. 30/30 refs: read loose references lazilymhagger@alum.mit.edu, Apr 24, 2012
  36. Junio C HamanoApr 25, 2012
  37. Michael HaggertyApr 26, 2012

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