From d46cd93b6a03f6614a91803fa7d027fc6b917bc1 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 10 Nov 2023 14:36:37 -0700
Subject: [PATCH] [map] Speed up copy-constructor

---
 src/hb-map.hh | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 275dcbe93..45a02b830 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -47,7 +47,29 @@ struct hb_hashmap_t
   hb_hashmap_t ()  { init (); }
   ~hb_hashmap_t () { fini (); }
 
-  hb_hashmap_t (const hb_hashmap_t& o) : hb_hashmap_t () { alloc (o.population); hb_copy (o, *this); }
+  hb_hashmap_t (const hb_hashmap_t& o) : hb_hashmap_t ()
+  {
+    if (unlikely (!o.mask)) return;
+
+    if (item_t::is_trivial)
+    {
+      items = (item_t *) hb_malloc (sizeof (item_t) * (o.mask + 1));
+      if (unlikely (!items))
+      {
+	successful = false;
+	return;
+      }
+      population = o.population;
+      occupancy = o.occupancy;
+      mask = o.mask;
+      prime = o.prime;
+      max_chain_length = o.max_chain_length;
+      memcpy (items, o.items, sizeof (item_t) * (mask + 1));
+      return;
+    }
+
+    alloc (o.population); hb_copy (o, *this);
+  }
   hb_hashmap_t (hb_hashmap_t&& o) : hb_hashmap_t () { hb_swap (*this, o); }
   hb_hashmap_t& operator= (const hb_hashmap_t& o)  { reset (); alloc (o.population); hb_copy (o, *this); return *this; }
   hb_hashmap_t& operator= (hb_hashmap_t&& o)  { hb_swap (*this, o); return *this; }