Merge branch 'nd/preallocate-hash'

When we know approximately how many entries we will have in the
hash-table, it makes sense to size the hash table to that number
from the beginning to avoid unnecessary rehashing.

* nd/preallocate-hash:
  Preallocate hash tables when the number of inserts are known in advance

1 files changed, 7 insertions, 0 deletions

diff --git a/hash.h b/hash.h
index b875ce67c4..1d43ac0ba0 100644
--- a/hash.h
+++ b/hash.h
@@ -40,4 +40,11 @@ static inline void init_hash(struct hash_table *table)
 	table->array = NULL;
 }
 
+static inline void preallocate_hash(struct hash_table *table, unsigned int elts)
+{
+	assert(table->size == 0 && table->nr == 0 && table->array == NULL);
+	table->size = elts * 2;
+	table->array = xcalloc(sizeof(struct hash_table_entry), table->size);
+}
+
 #endif