[11/11] hashmap_get_next returns "struct hashmap_entry *"
diff mbox series

Message ID 20190826024332.3403-12-e@80x24.org
State New
Headers show
Series
  • [01/11] diff: use hashmap_entry_init on moved_entry.ent
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Commit Message

Eric Wong Aug. 26, 2019, 2:43 a.m. UTC
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(-)

Comments

Derrick Stolee Aug. 27, 2019, 2:53 p.m. UTC | #1
On 8/25/2019 10:43 PM, Eric Wong wrote:
> 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);

>  		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.

>  				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.

> +		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
Eric Wong Aug. 30, 2019, 7:36 p.m. UTC | #2
Derrick Stolee <stolee@gmail.com> wrote:
> On 8/25/2019 10:43 PM, Eric Wong wrote:
> > --- 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.

Agreed, naming is hard :<

In the Linux kernel list.h implementation, there's actually
list_for_each_entry, list_next_entry and a bunch of other
macros which allow the caller to avoid using container_of.
We only have list_first_entry, so far.

We can draw inspiration from those macros by creating
hashmap_get_next_entry and hashmap_for_each_entry macros
which allow callers specify the type once; and there'd
be no need for callers to specify the hashmap_entry
pointer name at all :)

Unlike the kernel, it looks like we can't rely on __typeof__ in
git, but I think we can let the caller specify the type once...

Patch
diff mbox series

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);
 		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);
 				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);
+		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) {