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GHash: ensure function, avoids multiple lookups

This commit is contained in:
Campbell Barton 2015-04-06 19:55:08 +10:00
parent 3639a70eae
commit dd129125b6
2 changed files with 47 additions and 0 deletions
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1
source/blender/blenlib/BLI_ghash.h
View File

@ -79,6 +79,7 @@ bool BLI_ghash_reinsert(GHash *gh, void *key, void *val, GHashKeyFreeFP keyfre
void *BLI_ghash_lookup(GHash *gh, const void *key) ATTR_WARN_UNUSED_RESULT;
void *BLI_ghash_lookup_default(GHash *gh, const void *key, void *val_default) ATTR_WARN_UNUSED_RESULT;
void **BLI_ghash_lookup_p(GHash *gh, const void *key) ATTR_WARN_UNUSED_RESULT;
bool BLI_ghash_ensure_p(GHash *gh, void *key, void ***r_val) ATTR_WARN_UNUSED_RESULT;
bool BLI_ghash_remove(GHash *gh, void *key, GHashKeyFreeFP keyfreefp, GHashValFreeFP valfreefp);
void BLI_ghash_clear(GHash *gh, GHashKeyFreeFP keyfreefp, GHashValFreeFP valfreefp);
void BLI_ghash_clear_ex(GHash *gh, GHashKeyFreeFP keyfreefp, GHashValFreeFP valfreefp,

46
source/blender/blenlib/intern/BLI_ghash.c
View File

@ -444,6 +444,22 @@ BLI_INLINE void ghash_insert_ex(
ghash_buckets_expand(gh, ++gh->nentries, false);
}
/**
* Insert function that takes a pre-allocated entry.
*/
BLI_INLINE void ghash_insert_ex_keyonly_entry(
GHash *gh, void *key, const unsigned int bucket_index,
Entry *e)
{
BLI_assert((gh->flag & GHASH_FLAG_ALLOW_DUPES) || (BLI_ghash_haskey(gh, key) == 0));
e->next = gh->buckets[bucket_index];
e->key = key;
gh->buckets[bucket_index] = e;
ghash_buckets_expand(gh, ++gh->nentries, false);
}
/**
* Insert function that doesn't set the value (use for GSet)
*/
@ -720,6 +736,36 @@ void **BLI_ghash_lookup_p(GHash *gh, const void *key)
return e ? &e->val : NULL;
}
/**
* Ensure \a key is exists in \a gh.
*
* This handles the common situation where the caller needs ensure a key is added to \a gh,
* constructing a new value in the case the key isn't found.
* Otherwise use the existing value.
*
* Such situations typically incur multiple lookups, however this function
* avoids them by ensuring the key is added,
* returning a pointer to the value so it can be used or initialized by the caller.
*
* \returns true when the value didn't need to be added.
* (when false, the caller _must_ initialize the value).
*/
bool BLI_ghash_ensure_p(GHash *gh, void *key, void ***r_val)
{
const unsigned int hash = ghash_keyhash(gh, key);
const unsigned int bucket_index = ghash_bucket_index(gh, hash);
GHashEntry *e = (GHashEntry *)ghash_lookup_entry_ex(gh, key, bucket_index);
const bool haskey = (e != NULL);
if (!haskey) {
e = BLI_mempool_alloc(gh->entrypool);
ghash_insert_ex_keyonly_entry(gh, key, bucket_index, (Entry *)e);
}
*r_val = &e->val;
return haskey;
}
/**
* Remove \a key from \a gh, or return false if the key wasn't found.
*