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Re: [PATCH 11/11] hashmap_get_next returns "struct hashmap_entry *"

From
Derrick Stolee <stolee@gmail.com>
Date
Aug 27, 2019, 14:53 UTC
Message-ID
<2f22841c-779e-6d6e-19b7-0a119088e343@gmail.com>
In-Reply-To
<20190826024332.3403-12-e@80x24.org>
On 8/25/2019 10:43 PM, Eric Wong wrote:
Show 26 quoted lines
> This is a step towards removing the requirement for
> hashmap_entry being the first field of a struct.
> 
> Signed-off-by: Eric Wong <e@80x24.org>
> ---
>  diff.c                  | 19 ++++++++++++-------
>  diffcore-rename.c       | 11 +++++++----
>  hashmap.c               |  2 +-
>  hashmap.h               | 12 ++++++++----
>  name-hash.c             |  8 +++++---
>  t/helper/test-hashmap.c | 10 ++++++----
>  6 files changed, 39 insertions(+), 23 deletions(-)
> 
> diff --git a/diff.c b/diff.c
> index 72d3c6aa19..663b5d01f8 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -1035,8 +1035,10 @@ static void pmb_advance_or_null_multi_match(struct diff_options *o,
>  {
>  	int i;
>  	char *got_match = xcalloc(1, pmb_nr);
> +	struct hashmap_entry *ent = &match->ent;
>  
> -	for (; match; match = hashmap_get_next(hm, &match->ent)) {
> +	for (; ent; ent = hashmap_get_next(hm, ent)) {
> +		match = container_of(ent, struct moved_entry, ent);

Lines like this are very difficult to parse. In this container_of() macro, 'ent' is taking both the 'ptr' and 'member' values.

I would prefer that you make your local member be named something different, for instance:

	struct hashmap_entry *match_ent = &match->ent;
and
	match = container_of(match_ent, struct moved_entry, ent);
Show 55 quoted lines
>  		for (i = 0; i < pmb_nr; i++) {
>  			struct moved_entry *prev = pmb[i].match;
>  			struct moved_entry *cur = (prev && prev->next_line) ?
> @@ -1135,8 +1137,9 @@ static void mark_color_as_moved(struct diff_options *o,
>  
>  	for (n = 0; n < o->emitted_symbols->nr; n++) {
>  		struct hashmap *hm = NULL;
> +		struct hashmap_entry *ent = NULL;
>  		struct moved_entry *key;
> -		struct moved_entry *match = NULL;
> +		struct moved_entry *match;
>  		struct emitted_diff_symbol *l = &o->emitted_symbols->buf[n];
>  		enum diff_symbol last_symbol = 0;
>  
> @@ -1144,20 +1147,20 @@ static void mark_color_as_moved(struct diff_options *o,
>  		case DIFF_SYMBOL_PLUS:
>  			hm = del_lines;
>  			key = prepare_entry(o, n);
> -			match = hashmap_get(hm, &key->ent, NULL);
> +			ent = hashmap_get(hm, &key->ent, NULL);
>  			free(key);
>  			break;
>  		case DIFF_SYMBOL_MINUS:
>  			hm = add_lines;
>  			key = prepare_entry(o, n);
> -			match = hashmap_get(hm, &key->ent, NULL);
> +			ent = hashmap_get(hm, &key->ent, NULL);
>  			free(key);
>  			break;
>  		default:
>  			flipped_block = 0;
>  		}
>  
> -		if (!match) {
> +		if (!ent) {
>  			int i;
>  
>  			adjust_last_block(o, n, block_length);
> @@ -1169,6 +1172,7 @@ static void mark_color_as_moved(struct diff_options *o,
>  			last_symbol = l->s;
>  			continue;
>  		}
> +		match = container_of(ent, struct moved_entry, ent);
>  
>  		if (o->color_moved == COLOR_MOVED_PLAIN) {
>  			last_symbol = l->s;
> @@ -1189,8 +1193,9 @@ static void mark_color_as_moved(struct diff_options *o,
>  			 * The current line is the start of a new block.
>  			 * Setup the set of potential blocks.
>  			 */
> -			for (; match; match = hashmap_get_next(hm,
> -								&match->ent)) {
> +			for (; ent; ent = hashmap_get_next(hm, ent)) {
> +				match = container_of(ent, struct moved_entry,
> +							ent);
Same complaint here.
Show 31 quoted lines
>  				ALLOC_GROW(pmb, pmb_nr + 1, pmb_alloc);
>  				if (o->color_moved_ws_handling &
>  				    COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) {
> diff --git a/diffcore-rename.c b/diffcore-rename.c
> index 4670a40179..71aa240a68 100644
> --- a/diffcore-rename.c
> +++ b/diffcore-rename.c
> @@ -274,7 +274,7 @@ static int find_identical_files(struct hashmap *srcs,
>  				struct diff_options *options)
>  {
>  	int renames = 0;
> -
> +	struct hashmap_entry *ent;
>  	struct diff_filespec *target = rename_dst[dst_index].two;
>  	struct file_similarity *p, *best = NULL;
>  	int i = 100, best_score = -1;
> @@ -282,12 +282,15 @@ static int find_identical_files(struct hashmap *srcs,
>  	/*
>  	 * Find the best source match for specified destination.
>  	 */
> -	p = hashmap_get_from_hash(srcs,
> +	ent = hashmap_get_from_hash(srcs,
>  				  hash_filespec(options->repo, target),
>  				  NULL);
> -	for (; p; p = hashmap_get_next(srcs, &p->entry)) {
> +	for (; ent; ent = hashmap_get_next(srcs, ent)) {
>  		int score;
> -		struct diff_filespec *source = p->filespec;
> +		struct diff_filespec *source;
> +
> +		p = container_of(ent, struct file_similarity, entry);
This is slightly better, but still a bit confusing.
Show 105 quoted lines
> +		source = p->filespec;
>  
>  		/* False hash collision? */
>  		if (!oideq(&source->oid, &target->oid))
> diff --git a/hashmap.c b/hashmap.c
> index 2dd9912e13..d6434d9ca4 100644
> --- a/hashmap.c
> +++ b/hashmap.c
> @@ -192,7 +192,7 @@ void *hashmap_get(const struct hashmap *map, const struct hashmap_entry *key,
>  	return *find_entry_ptr(map, key, keydata);
>  }
>  
> -void *hashmap_get_next(const struct hashmap *map,
> +struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
>  			const struct hashmap_entry *entry)
>  {
>  	struct hashmap_entry *e = entry->next;
> diff --git a/hashmap.h b/hashmap.h
> index b62ee2e7b9..25643dcdc4 100644
> --- a/hashmap.h
> +++ b/hashmap.h
> @@ -55,15 +55,19 @@
>   *
>   *         if (!strcmp("print_all_by_key", action)) {
>   *             struct long2string k, *e;
> + *             struct hashmap_entry *ent;
>   *             hashmap_entry_init(&k->ent, memhash(&key, sizeof(long)));
>   *             k.key = key;
>   *
>   *             flags &= ~COMPARE_VALUE;
> - *             e = hashmap_get(&map, &k, NULL);
> - *             if (e) {
> + *             ent = hashmap_get(&map, &k, NULL);
> + *             if (ent) {
> + *                 e = container_of(ent, struct long2string, ent);
>   *                 printf("first: %ld %s\n", e->key, e->value);
> - *                 while ((e = hashmap_get_next(&map, e)))
> + *                 while ((ent = hashmap_get_next(&map, ent))) {
> + *                     e = container_of(ent, struct long2string, ent);
>   *                     printf("found more: %ld %s\n", e->key, e->value);
> + *                 }
>   *             }
>   *         }
>   *
> @@ -320,7 +324,7 @@ static inline void *hashmap_get_from_hash(const struct hashmap *map,
>   * `entry` is the hashmap_entry to start the search from, obtained via a previous
>   * call to `hashmap_get` or `hashmap_get_next`.
>   */
> -void *hashmap_get_next(const struct hashmap *map,
> +struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
>  			const struct hashmap_entry *entry);
>  
>  /*
> diff --git a/name-hash.c b/name-hash.c
> index f64c52bfa2..6f2779934f 100644
> --- a/name-hash.c
> +++ b/name-hash.c
> @@ -703,15 +703,17 @@ void adjust_dirname_case(struct index_state *istate, char *name)
>  struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
>  {
>  	struct cache_entry *ce;
> +	struct hashmap_entry *ent;
>  
>  	lazy_init_name_hash(istate);
>  
> -	ce = hashmap_get_from_hash(&istate->name_hash,
> +	ent = hashmap_get_from_hash(&istate->name_hash,
>  				   memihash(name, namelen), NULL);
> -	while (ce) {
> +	while (ent) {
> +		ce = container_of(ent, struct cache_entry, ent);
>  		if (same_name(ce, name, namelen, icase))
>  			return ce;
> -		ce = hashmap_get_next(&istate->name_hash, &ce->ent);
> +		ent = hashmap_get_next(&istate->name_hash, ent);
>  	}
>  	return NULL;
>  }
> diff --git a/t/helper/test-hashmap.c b/t/helper/test-hashmap.c
> index de2bd083b9..d85b8dc58e 100644
> --- a/t/helper/test-hashmap.c
> +++ b/t/helper/test-hashmap.c
> @@ -194,16 +194,18 @@ int cmd__hashmap(int argc, const char **argv)
>  			free(entry);
>  
>  		} else if (!strcmp("get", cmd) && p1) {
> +			struct hashmap_entry *e;
>  
>  			/* lookup entry in hashmap */
> -			entry = hashmap_get_from_hash(&map, hash, p1);
> +			e = hashmap_get_from_hash(&map, hash, p1);
>  
>  			/* print result */
> -			if (!entry)
> +			if (!e)
>  				puts("NULL");
> -			while (entry) {
> +			while (e) {
> +				entry = container_of(e, struct test_entry, ent);
>  				puts(get_value(entry));
> -				entry = hashmap_get_next(&map, &entry->ent);
> +				e = hashmap_get_next(&map, e);
>  			}
>  
>  		} else if (!strcmp("remove", cmd) && p1) {

I didn't comment on them all, but essentially every use of container_of() here is pretty confusing with the names. Perhaps some pattern of "type_member" could be helpful, so you can use

	type_p = container_of(type_member, struct type, member);
to be really clear about each name.

Thanks, -Stolee

Previous: Eric WongNext: Eric Wong
Message 29 of 71 in “hashmap: bugfixes, safety fixes, and WIP improvements”
  1. 00/11 hashmap: bugfixes, safety fixes, and WIP improvementsEric Wong, Aug 26, 2019
  2. 01/11 diff: use hashmap_entry_init on moved_entry.entEric Wong, Aug 26, 2019
  3. Derrick StoleeAug 27, 2019
  4. 02/11 packfile: use hashmap_entry in delta_base_cache_entryEric Wong, Aug 26, 2019
  5. 03/11 hashmap_entry_init takes "struct hashmap_entry *"Eric Wong, Aug 26, 2019
  6. Derrick StoleeAug 27, 2019
  7. Johannes SchindelinAug 28, 2019
  8. Eric WongAug 30, 2019
  9. Johannes SchindelinSep 2, 2019
  10. 04/11 hashmap_entry: detect improper initializationEric Wong, Aug 26, 2019
  11. Johannes SchindelinAug 27, 2019
  12. Eric WongAug 27, 2019
  13. Junio C HamanoAug 27, 2019
  14. Johannes SchindelinAug 28, 2019
  15. Phillip WoodAug 28, 2019
  16. Eric WongAug 30, 2019
  17. 04/11 coccicheck: detect hashmap_entry.hash assignmentEric Wong, Sep 8, 2019
  18. Junio C HamanoSep 9, 2019
  19. 05/11 hashmap_get_next takes "const struct hashmap_entry *"Eric Wong, Aug 26, 2019
  20. 06/11 hashmap_add takes "struct hashmap_entry *"Eric Wong, Aug 26, 2019
  21. 07/11 hashmap_get takes "const struct hashmap_entry *"Eric Wong, Aug 26, 2019
  22. 08/11 hashmap_remove takes "const struct hashmap_entry *"Eric Wong, Aug 26, 2019
  23. 09/11 hashmap_put takes "struct hashmap_entry *"Eric Wong, Aug 26, 2019
  24. 10/11 introduce container_of macroEric Wong, Aug 26, 2019
  25. Derrick StoleeAug 27, 2019
  26. Phillip WoodAug 28, 2019
  27. Eric WongAug 30, 2019
  28. 11/11 hashmap_get_next returns "struct hashmap_entry *"Eric Wong, Aug 26, 2019
  29. Derrick StoleeAug 27, 2019
  30. Eric WongAug 30, 2019
  31. 00/19 hashmap bug/safety/ease-of-use fixesEric Wong, Sep 24, 2019
  32. 01/19 diff: use hashmap_entry_init on moved_entry.entEric Wong, Sep 24, 2019
  33. 02/19 coccicheck: detect hashmap_entry.hash assignmentEric Wong, Sep 24, 2019
  34. Derrick StoleeSep 25, 2019
  35. 03/19 packfile: use hashmap_entry in delta_base_cache_entryEric Wong, Sep 24, 2019
  36. 04/19 hashmap_entry_init takes "struct hashmap_entry *"Eric Wong, Sep 24, 2019
  37. Derrick StoleeSep 25, 2019
  38. 05/19 hashmap_get_next takes "const struct hashmap_entry *"Eric Wong, Sep 24, 2019
  39. 06/19 hashmap_add takes "struct hashmap_entry *"Eric Wong, Sep 24, 2019
  40. 07/19 hashmap_get takes "const struct hashmap_entry *"Eric Wong, Sep 24, 2019
  41. Derrick StoleeSep 25, 2019
  42. Eric WongSep 30, 2019
  43. 08/19 hashmap_remove takes "const struct hashmap_entry *"Eric Wong, Sep 24, 2019
  44. Derrick StoleeSep 25, 2019
  45. 09/19 hashmap_put takes "struct hashmap_entry *"Eric Wong, Sep 24, 2019
  46. 10/19 introduce container_of macroEric Wong, Sep 24, 2019
  47. Derrick StoleeSep 25, 2019
  48. Eric WongSep 30, 2019
  49. 11/19 hashmap_get_next returns "struct hashmap_entry *"Eric Wong, Sep 24, 2019
  50. Derrick StoleeSep 25, 2019
  51. 12/19 hashmap: use *_entry APIs to wrap container_ofEric Wong, Sep 24, 2019
  52. Derrick StoleeSep 25, 2019
  53. 13/19 hashmap_get{,_from_hash} return "struct hashmap_entry *"Eric Wong, Sep 24, 2019
  54. 14/19 hashmap_cmp_fn takes hashmap_entry paramsEric Wong, Sep 24, 2019
  55. 15/19 hashmap: use *_entry APIs for iterationEric Wong, Sep 24, 2019
  56. 16/19 hashmap: hashmap_{put,remove} return hashmap_entry *Eric Wong, Sep 24, 2019
  57. 17/19 hashmap: introduce hashmap_free_entriesEric Wong, Sep 24, 2019
  58. 18/19 OFFSETOF_VAR macro to simplify hashmap iteratorsEric Wong, Sep 24, 2019
  59. Junio C HamanoSep 30, 2019
  60. Junio C HamanoOct 4, 2019
  61. Eric WongOct 4, 2019
  62. Junio C HamanoOct 4, 2019
  63. Eric WongOct 4, 2019
  64. Junio C HamanoOct 6, 2019
  65. 19/19 hashmap: remove type arg from hashmap_{get,put,remove}_entryEric Wong, Sep 24, 2019
  66. Derrick StoleeSep 25, 2019
  67. Derrick StoleeSep 25, 2019
  68. Johannes SchindelinSep 26, 2019
  69. Eric WongSep 30, 2019
  70. Phillip WoodSep 26, 2019
  71. Junio C HamanoSep 29, 2019

Read the whole thread, see it on lore, or plain text.

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