From cbcdf442c505b1461ef9591d1eedd849237a279b Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 26 May 2022 11:20:27 -0600
Subject: [PATCH] [map] Speed up map's own hash()

---
 src/hb-map.hh | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 11dbe191c..d146b804c 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -100,6 +100,9 @@ struct hb_hashmap_t
       return key != kinv && value != vinv;
     }
     hb_pair_t<K, V> get_pair() const { return hb_pair_t<K, V> (key, value); }
+
+    uint32_t total_hash () const
+    { return (hash * 31) + hb_hash (value); }
   };
 
   hb_object_header_t header;
@@ -242,9 +245,9 @@ struct hb_hashmap_t
   uint32_t hash () const
   {
     uint32_t h = 0;
-    /* TODO: Speed-up since we have the hash of the key already in the item. */
-    for (auto pair : iter ())
-      h ^= (hb_hash (pair.first) * 31) + hb_hash (pair.second);
+    for (const auto &item : + hb_array (items, mask ? mask + 1 : 0)
+			    | hb_filter (&item_t::is_real))
+      h ^= item.total_hash ();
     return h;
   }