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Re: [PATCH v2 3/8] string-list: return index directly when inserting an existing element

From
Patrick Steinhardt <ps@pks.im>
Date
May 19, 2025, 07:18 UTC
Message-ID
<aCrbKI_c5Bma8ZDQ@pks.im>
In-Reply-To
<aCoDW8CcWeq8T9hp@ArchLinux>
On Sun, May 18, 2025 at 11:57:15PM +0800, shejialuo wrote:
Show 38 quoted lines
> When inserting an existing element, "add_entry" would convert "index"
> value to "-1-index" to indicate the caller that this element is in the
> list already.
> 
> However, in "string_list_insert", we would simply convert this to the
> original positive index without any further action. Let's directly
> return the index as we don't care about whether the element is in the
> list by using "add_entry".
> 
> In the future, if we want to let "add_entry" tell the caller, we may add
> "int *exact_match" parameter to "add_entry" instead of converting the
> index to negative to indicate.
> 
> Signed-off-by: shejialuo <shejialuo@gmail.com>
> ---
>  string-list.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/string-list.c b/string-list.c
> index 8540c29bc9..171cef5dbb 100644
> --- a/string-list.c
> +++ b/string-list.c
> @@ -40,14 +40,13 @@ static int get_entry_index(const struct string_list *list, const char *string,
>  	return right;
>  }
>  
> -/* returns -1-index if already exists */
>  static int add_entry(struct string_list *list, const char *string)
>  {
>  	int exact_match = 0;
>  	int index = get_entry_index(list, string, &exact_match);
>  
>  	if (exact_match)
> -		return -1 - index;
> +		return index;
>  
>  	ALLOC_GROW(list->items, list->nr+1, list->alloc);
>  	if (index < list->nr)

Okay, let's assume that "index == 2" here and we have an exact match. We'd thus return `-1 - 2 == -3`.

Show 9 quoted lines
> @@ -65,9 +64,6 @@ struct string_list_item *string_list_insert(struct string_list *list, const char
>  {
>  	int index = add_entry(list, string);
>  
> -	if (index < 0)
> -		index = -1 - index;
> -
>  	return list->items + index;
>  }

So we'd now realize that `index < 0` and thus calculate `-1 - -3 == 2`, which is the original index indeed. So this is a nice simplification that retains the original behaviour indeed.

I think we could simplify the code even further by inlining `get_entry_index()` now that `string_list_insert()` is a trivial wrapper around it. But I'll leave it up to you whether we want to do it or not.

Patrick
Previous: shejialuoNext: shejialuo
Message 27 of 52 in “enhance "string_list" code and test”
  1. 0/5 enhance "string_list" code and testshejialuo, Apr 22, 2025
  2. 1/5 string-list: fix sign compare warningsshejialuo, Apr 22, 2025
  3. Junio C HamanoApr 22, 2025
  4. shejialuoApr 24, 2025
  5. 2/5 u-string-list: move "test_split" into "u-string-list.c"shejialuo, Apr 22, 2025
  6. Junio C HamanoApr 22, 2025
  7. shejialuoApr 24, 2025
  8. Patrick SteinhardtApr 23, 2025
  9. shejialuoApr 24, 2025
  10. 3/5 u-string-list: move "test_split_in_place" to "u-string-list.c"shejialuo, Apr 22, 2025
  11. Patrick SteinhardtApr 23, 2025
  12. 4/5 u-string-list: move "filter string" test to "u-string-list.c"shejialuo, Apr 22, 2025
  13. 5/5 u-string-list: move "remove duplicates" test to "u-string-list.c"shejialuo, Apr 22, 2025
  14. Patrick SteinhardtApr 23, 2025
  15. shejialuoApr 24, 2025
  16. 0/8 enhance "string_list" code and testshejialuo, May 18, 2025
  17. 1/8 string-list: fix sign compare warnings for loop iteratorshejialuo, May 18, 2025
  18. Patrick SteinhardtMay 19, 2025
  19. shejialuoMay 26, 2025
  20. 2/8 string-list: remove unused "insert_at" parameter from add_entryshejialuo, May 18, 2025
  21. Patrick SteinhardtMay 19, 2025
  22. shejialuoMay 26, 2025
  23. Jeff KingMay 19, 2025
  24. shejialuoMay 26, 2025
  25. Patrick SteinhardtMay 26, 2025
  26. 3/8 string-list: return index directly when inserting an existing elementshejialuo, May 18, 2025
  27. Patrick SteinhardtMay 19, 2025
  28. shejialuoMay 26, 2025
  29. Jeff KingMay 19, 2025
  30. shejialuoMay 26, 2025
  31. 4/8 string-list: enable sign compare warnings checkshejialuo, May 18, 2025
  32. Patrick SteinhardtMay 19, 2025
  33. shejialuoMay 26, 2025
  34. 5/8 u-string-list: move "test_split" into "u-string-list.c"shejialuo, May 18, 2025
  35. Patrick SteinhardtMay 19, 2025
  36. 6/8 u-string-list: move "test_split_in_place" to "u-string-list.c"shejialuo, May 18, 2025
  37. 7/8 u-string-list: move "filter string" test to "u-string-list.c"shejialuo, May 18, 2025
  38. Patrick SteinhardtMay 19, 2025
  39. shejialuoMay 26, 2025
  40. 8/8 u-string-list: move "remove duplicates" test to "u-string-list.c"shejialuo, May 18, 2025
  41. Patrick SteinhardtMay 19, 2025
  42. 0/8 enhance "string_list" code and testshejialuo, Jun 29, 2025
  43. 1/8 string-list: fix sign compare warnings for loop iteratorshejialuo, Jun 29, 2025
  44. 2/8 string-list: remove unused "insert_at" parameter from add_entryshejialuo, Jun 29, 2025
  45. 3/8 string-list: return index directly when inserting an existing elementshejialuo, Jun 29, 2025
  46. 4/8 string-list: enable sign compare warnings checkshejialuo, Jun 29, 2025
  47. 5/8 u-string-list: move "test_split" into "u-string-list.c"shejialuo, Jun 29, 2025
  48. 6/8 u-string-list: move "test_split_in_place" to "u-string-list.c"shejialuo, Jun 29, 2025
  49. 7/8 u-string-list: move "filter string" test to "u-string-list.c"shejialuo, Jun 29, 2025
  50. 8/8 u-string-list: move "remove duplicates" test to "u-string-list.c"shejialuo, Jun 29, 2025
  51. Patrick SteinhardtJul 4, 2025
  52. Junio C HamanoJul 7, 2025

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