ghash and edgehash api, allow newly defined hashes to take in the size of the hash as an arg (avoids resizing in simple cases when the hash is created and filled immediately).

1 files changed, 19 insertions, 2 deletions

diff --git a/source/blender/blenlib/intern/edgehash.c b/source/blender/blenlib/intern/edgehash.c
index 3263c69ee6a..738f1f0c7a1 100644
--- a/source/blender/blenlib/intern/edgehash.c
+++ b/source/blender/blenlib/intern/edgehash.c
@@ -86,6 +86,11 @@ struct EdgeHash {
 
 #define EDGE_HASH(v0, v1)  ((v0 * 39) ^ (v1 * 31))
 
+BLI_INLINE bool edgehash_test_expand_buckets(const unsigned int nentries, const unsigned int nbuckets)
+{
+	return (nentries > nbuckets / 2);
+}
+
 BLI_INLINE unsigned int edgehash_keyhash(EdgeHash *eh, unsigned int v0, unsigned int v1)
 {
 	BLI_assert(v0 < v1);
@@ -130,7 +135,7 @@ static void edgehash_insert_ex(EdgeHash *eh, unsigned int v0, unsigned int v1, v
 	e->val = val;
 	eh->buckets[hash] = e;
 
-	if (UNLIKELY(++eh->nentries > eh->nbuckets / 2)) {
+	if (UNLIKELY(edgehash_test_expand_buckets(++eh->nentries, eh->nbuckets))) {
 		EdgeEntry **old = eh->buckets;
 		const unsigned int nold = eh->nbuckets;
 		unsigned int i;
@@ -157,7 +162,7 @@ static void edgehash_insert_ex(EdgeHash *eh, unsigned int v0, unsigned int v1, v
 
 /* Public API */
 
-EdgeHash *BLI_edgehash_new(void)
+EdgeHash *BLI_edgehash_new_ex(const unsigned int nentries_reserve)
 {
 	EdgeHash *eh = MEM_callocN(sizeof(*eh), "EdgeHash");
 
@@ -166,12 +171,24 @@ EdgeHash *BLI_edgehash_new(void)
 	eh->cursize = 0;
 	eh->flag = 0;
 
+	/* if we have reserved the number of elements that this hash will contain */
+	if (nentries_reserve) {
+		while (edgehash_test_expand_buckets(nentries_reserve, eh->nbuckets)) {
+			eh->nbuckets = _ehash_hashsizes[++eh->cursize];
+		}
+	}
+
 	eh->buckets = MEM_callocN(eh->nbuckets * sizeof(*eh->buckets), "eh buckets 2");
 	eh->epool = BLI_mempool_create(sizeof(EdgeEntry), 512, 512, BLI_MEMPOOL_SYSMALLOC);
 
 	return eh;
 }
 
+EdgeHash *BLI_edgehash_new(void)
+{
+	return BLI_edgehash_new_ex(0);
+}
+
 /**
  * Insert edge (\a v0, \a v1) into hash with given value, does
  * not check for duplicates.