From 4f58ae60eb781b9ade164c4ea2abad708d00f4ce Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 10:13:55 -0600
Subject: [PATCH 01/23] [map] Keep is_used, is_tombstone as booleans

---
 src/hb-map.hh | 44 ++++++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 3084d478d..3df31ed98 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -71,6 +71,16 @@ struct hb_hashmap_t
     uint32_t hash;
     V value;
 
+    bool is_used_;
+    bool is_tombstone_;
+
+
+    bool is_used () const { return is_used_; }
+    void set_used (bool is_used) { is_used_ = is_used; }
+    bool is_tombstone () const { return is_tombstone_; }
+    void set_tombstone (bool is_tombstone) { is_tombstone_ = is_tombstone; }
+    bool is_real () const { return is_used_ && !is_tombstone_; }
+
     void clear ()
     {
       new (std::addressof (key)) K ();
@@ -78,27 +88,12 @@ struct hb_hashmap_t
       new (std::addressof (value)) V ();
       value = hb_coerce<V> (vINVALID);
       hash = 0;
+      is_used_ = false;
+      is_tombstone_ = false;
     }
 
     bool operator == (const K &o) { return hb_deref (key) == hb_deref (o); }
     bool operator == (const item_t &o) { return *this == o.key; }
-    bool is_unused () const
-    {
-      const K inv = hb_coerce<K> (kINVALID);
-      return key == inv;
-    }
-    bool is_tombstone () const
-    {
-      const K kinv = hb_coerce<K> (kINVALID);
-      const V vinv = hb_coerce<V> (vINVALID);
-      return key != kinv && value == vinv;
-    }
-    bool is_real () const
-    {
-      const K kinv = hb_coerce<K> (kINVALID);
-      const V vinv = hb_coerce<V> (vINVALID);
-      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
@@ -213,7 +208,7 @@ struct hb_hashmap_t
     return items[i].is_real () && items[i] == key ? items[i].value : hb_coerce<V> (vINVALID);
   }
 
-  void del (K key) { set (key, hb_coerce<V> (vINVALID)); }
+  void del (K key) { set_with_hash (key, hb_hash (key), hb_coerce<V> (vINVALID), true); }
 
   /* Has interface. */
   typedef V value_t;
@@ -297,7 +292,7 @@ struct hb_hashmap_t
   protected:
 
   template <typename VV>
-  bool set_with_hash (K key, uint32_t hash, VV&& value)
+  bool set_with_hash (K key, uint32_t hash, VV&& value, bool is_delete=false)
   {
     if (unlikely (!successful)) return false;
     const K kinv = hb_coerce<K> (kINVALID);
@@ -305,11 +300,10 @@ struct hb_hashmap_t
     if (unlikely ((occupancy + occupancy / 2) >= mask && !resize ())) return false;
     unsigned int i = bucket_for_hash (key, hash);
 
-    const V vinv = hb_coerce<V> (vINVALID);
-    if (value == vinv && items[i].key != key)
+    if (is_delete && items[i].key != key)
       return true; /* Trying to delete non-existent key. */
 
-    if (!items[i].is_unused ())
+    if (items[i].is_used ())
     {
       occupancy--;
       if (!items[i].is_tombstone ())
@@ -319,9 +313,11 @@ struct hb_hashmap_t
     items[i].key = key;
     items[i].value = value;
     items[i].hash = hash;
+    items[i].set_used (true);
+    items[i].set_tombstone (is_delete);
 
     occupancy++;
-    if (!items[i].is_tombstone ())
+    if (!is_delete)
       population++;
 
     return true;
@@ -337,7 +333,7 @@ struct hb_hashmap_t
     unsigned int i = hash % prime;
     unsigned int step = 0;
     unsigned int tombstone = (unsigned) -1;
-    while (!items[i].is_unused ())
+    while (items[i].is_used ())
     {
       if (items[i].hash == hash && items[i] == key)
 	return i;

From 5328b73fbaf5b952cf7eb23a7b4a228585502c10 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 10:32:56 -0600
Subject: [PATCH 02/23] [map] Reduce map item size again

---
 src/hb-map.hh | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 3df31ed98..7eb823e5e 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -68,11 +68,11 @@ struct hb_hashmap_t
   struct item_t
   {
     K key;
-    uint32_t hash;
+    uint32_t hash : 30;
+    uint32_t is_used_ : 1;
+    uint32_t is_tombstone_ : 1;
     V value;
 
-    bool is_used_;
-    bool is_tombstone_;
 
 
     bool is_used () const { return is_used_; }
@@ -330,6 +330,7 @@ struct hb_hashmap_t
 
   unsigned int bucket_for_hash (K key, uint32_t hash) const
   {
+    hash &= 0x3FFFFFFF; // We only store lower 30bit of hash
     unsigned int i = hash % prime;
     unsigned int step = 0;
     unsigned int tombstone = (unsigned) -1;

From 3f6a8f69a099398ac397bb652e6d8332167f6538 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 10:36:07 -0600
Subject: [PATCH 03/23] [map] Remove invalid-key special-casing

Can override invalid-key value now.
---
 src/hb-map.hh   |  3 ---
 src/test-map.cc | 15 ++++++---------
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 7eb823e5e..a0ab17a23 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -84,7 +84,6 @@ struct hb_hashmap_t
     void clear ()
     {
       new (std::addressof (key)) K ();
-      key = hb_coerce<K> (kINVALID);
       new (std::addressof (value)) V ();
       value = hb_coerce<V> (vINVALID);
       hash = 0;
@@ -295,8 +294,6 @@ struct hb_hashmap_t
   bool set_with_hash (K key, uint32_t hash, VV&& value, bool is_delete=false)
   {
     if (unlikely (!successful)) return false;
-    const K kinv = hb_coerce<K> (kINVALID);
-    if (unlikely (key == kinv)) return true;
     if (unlikely ((occupancy + occupancy / 2) >= mask && !resize ())) return false;
     unsigned int i = bucket_for_hash (key, hash);
 
diff --git a/src/test-map.cc b/src/test-map.cc
index 3041195a6..a5e85074c 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -168,9 +168,8 @@ main (int argc, char **argv)
     m1.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
     m2.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
 
-    /* Cannot override empty map. */
-    assert (m1.get (hb_map_t ()) == hb_map_t ());
-    assert (m2.get (hb_map_t ()) == hb_map_t ());
+    assert (m1.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
+    assert (m2.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
 
     assert (m1.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
     assert (m2.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
@@ -190,9 +189,8 @@ main (int argc, char **argv)
     m1.set (hb_set_t {1, 1000}, hb_set_t {2});
     m2.set (hb_set_t {1, 1000}, hb_set_t {2});
 
-    /* Cannot override empty set. */
-    assert (m1.get (hb_set_t ()) == hb_set_t ());
-    assert (m2.get (hb_set_t ()) == hb_set_t ());
+    assert (m1.get (hb_set_t ()) == hb_set_t {1});
+    assert (m2.get (hb_set_t ()) == hb_set_t {1});
 
     assert (m1.get (hb_set_t {1000, 1}) == hb_set_t {2});
     assert (m2.get (hb_set_t {1000, 1}) == hb_set_t {2});
@@ -214,9 +212,8 @@ main (int argc, char **argv)
     m1.set (vector_t {1}, vector_t {2});
     m2.set (vector_t {1}, vector_t {2});
 
-    /* Cannot override empty vector. */
-    assert (m1.get (vector_t ()) == vector_t ());
-    assert (m2.get (vector_t ()) == vector_t ());
+    assert (m1.get (vector_t ()) == vector_t {1});
+    assert (m2.get (vector_t ()) == vector_t {1});
 
     assert (m1.get (vector_t {1}) == vector_t {2});
     assert (m2.get (vector_t {1}) == vector_t {2});

From 0ccab339f98ab7af27b3ca0db8489ff836ca11f3 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 10:43:36 -0600
Subject: [PATCH 04/23] [map] Remove invalid-key template arguments since
 unused

---
 src/hb-map.hh                    |  6 ------
 src/hb-ot-post-table-v2subset.hh |  2 +-
 src/hb-serialize.hh              |  3 +--
 src/test-map.cc                  | 26 +++++++++++++-------------
 4 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index a0ab17a23..c62b9d7bb 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -35,9 +35,7 @@
  */
 
 template <typename K, typename V,
-	  typename k_invalid_t = K,
 	  typename v_invalid_t = V,
-	  k_invalid_t kINVALID = std::is_pointer<K>::value ? 0 : std::is_signed<K>::value ? hb_int_min (K) : (K) -1,
 	  v_invalid_t vINVALID = std::is_pointer<V>::value ? 0 : std::is_signed<V>::value ? hb_int_min (V) : (V) -1>
 struct hb_hashmap_t
 {
@@ -401,15 +399,11 @@ struct hb_hashmap_t
 struct hb_map_t : hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID,
 			       HB_MAP_VALUE_INVALID>
 {
   using hashmap = hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID,
 			       HB_MAP_VALUE_INVALID>;
 
   ~hb_map_t () = default;
diff --git a/src/hb-ot-post-table-v2subset.hh b/src/hb-ot-post-table-v2subset.hh
index c817b28e6..8c0312fa4 100644
--- a/src/hb-ot-post-table-v2subset.hh
+++ b/src/hb-ot-post-table-v2subset.hh
@@ -78,7 +78,7 @@ HB_INTERNAL bool postV2Tail::subset (hb_subset_context_t *c) const
 
   post::accelerator_t _post (c->plan->source);
 
-  hb_hashmap_t<hb_bytes_t, unsigned, std::nullptr_t, unsigned, nullptr, (unsigned)-1> glyph_name_to_new_index;
+  hb_hashmap_t<hb_bytes_t, unsigned> glyph_name_to_new_index;
   for (hb_codepoint_t new_gid = 0; new_gid < num_glyphs; new_gid++)
   {
     hb_codepoint_t old_gid = reverse_glyph_map.get (new_gid);
diff --git a/src/hb-serialize.hh b/src/hb-serialize.hh
index 5663b290c..3f4535ce4 100644
--- a/src/hb-serialize.hh
+++ b/src/hb-serialize.hh
@@ -720,8 +720,7 @@ struct hb_serialize_context_t
 
   /* Map view of packed objects. */
   hb_hashmap_t<const object_t *, objidx_t,
-	       const object_t *, objidx_t,
-	       nullptr, 0> packed_map;
+	       objidx_t, 0> packed_map;
 };
 
 #endif /* HB_SERIALIZE_HH */
diff --git a/src/test-map.cc b/src/test-map.cc
index a5e85074c..e62f65091 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -127,19 +127,19 @@ main (int argc, char **argv)
 
   /* Test class key / value types. */
   {
-    hb_hashmap_t<hb_bytes_t, int, std::nullptr_t, int, nullptr, 0> m1;
-    hb_hashmap_t<int, hb_bytes_t, int, std::nullptr_t, 0, nullptr> m2;
-    hb_hashmap_t<hb_bytes_t, hb_bytes_t, std::nullptr_t, std::nullptr_t, nullptr, nullptr> m3;
+    hb_hashmap_t<hb_bytes_t, int, int, 0> m1;
+    hb_hashmap_t<int, hb_bytes_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<hb_bytes_t, hb_bytes_t, std::nullptr_t, nullptr> m3;
     assert (m1.get_population () == 0);
     assert (m2.get_population () == 0);
     assert (m3.get_population () == 0);
   }
 
   {
-    hb_hashmap_t<int, int, int, int, 0, 0> m0;
-    hb_hashmap_t<std::string, int, const std::string*, int, &invalid, 0> m1;
-    hb_hashmap_t<int, std::string, int, const std::string*, 0, &invalid> m2;
-    hb_hashmap_t<std::string, std::string, const std::string*, const std::string*, &invalid, &invalid> m3;
+    hb_hashmap_t<int, int, int, 0> m0;
+    hb_hashmap_t<std::string, int, int, 0> m1;
+    hb_hashmap_t<int, std::string, const std::string*, &invalid> m2;
+    hb_hashmap_t<std::string, std::string, const std::string*, &invalid> m3;
 
     std::string s;
     for (unsigned i = 1; i < 1000; i++)
@@ -156,8 +156,8 @@ main (int argc, char **argv)
   {
     using pair = hb_pair_t<hb_codepoint_t, hb_codepoint_t>;
 
-    hb_hashmap_t<hb_map_t, hb_map_t, const hb_map_t *, const hb_map_t *, &invalid_map, &invalid_map> m1;
-    hb_hashmap_t<hb_map_t, hb_map_t, std::nullptr_t, std::nullptr_t, nullptr, nullptr> m2;
+    hb_hashmap_t<hb_map_t, hb_map_t, const hb_map_t *, &invalid_map> m1;
+    hb_hashmap_t<hb_map_t, hb_map_t, std::nullptr_t, nullptr> m2;
 
     m1.set (hb_map_t (), hb_map_t {});
     m2.set (hb_map_t (), hb_map_t {});
@@ -177,8 +177,8 @@ main (int argc, char **argv)
 
   /* Test hashing sets. */
   {
-    hb_hashmap_t<hb_set_t, hb_set_t, const hb_set_t *, const hb_set_t *, &invalid_set, &invalid_set> m1;
-    hb_hashmap_t<hb_set_t, hb_set_t, std::nullptr_t, std::nullptr_t, nullptr, nullptr> m2;
+    hb_hashmap_t<hb_set_t, hb_set_t, const hb_set_t *, &invalid_set> m1;
+    hb_hashmap_t<hb_set_t, hb_set_t, std::nullptr_t, nullptr> m2;
 
     m1.set (hb_set_t (), hb_set_t ());
     m2.set (hb_set_t (), hb_set_t ());
@@ -200,8 +200,8 @@ main (int argc, char **argv)
   {
     using vector_t = hb_vector_t<unsigned>;
 
-    hb_hashmap_t<vector_t, vector_t, const vector_t *, const vector_t *, &invalid_vector, &invalid_vector> m1;
-    hb_hashmap_t<vector_t, vector_t, std::nullptr_t, std::nullptr_t, nullptr, nullptr> m2;
+    hb_hashmap_t<vector_t, vector_t, const vector_t *, &invalid_vector> m1;
+    hb_hashmap_t<vector_t, vector_t, std::nullptr_t, nullptr> m2;
 
     m1.set (vector_t (), vector_t ());
     m2.set (vector_t (), vector_t ());

From 3f78a71ca059b461f79d0ee64766c7c3f4327b14 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:11:35 -0600
Subject: [PATCH 05/23] [map] Finally! Just can usd hb_hashmap_t<obj_t, obj_t>

Yay!
---
 src/hb-map.hh                    | 29 ++++++++++-----------
 src/hb-ot-post-table-v2subset.hh |  2 +-
 src/hb-serialize.hh              |  3 +--
 src/test-map.cc                  | 43 ++++++++------------------------
 4 files changed, 27 insertions(+), 50 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index c62b9d7bb..9b435c7d7 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -35,8 +35,7 @@
  */
 
 template <typename K, typename V,
-	  typename v_invalid_t = V,
-	  v_invalid_t vINVALID = std::is_pointer<V>::value ? 0 : std::is_signed<V>::value ? hb_int_min (V) : (V) -1>
+	  bool minus_one = false>
 struct hb_hashmap_t
 {
   hb_hashmap_t ()  { init (); }
@@ -71,19 +70,24 @@ struct hb_hashmap_t
     uint32_t is_tombstone_ : 1;
     V value;
 
-
-
     bool is_used () const { return is_used_; }
     void set_used (bool is_used) { is_used_ = is_used; }
     bool is_tombstone () const { return is_tombstone_; }
     void set_tombstone (bool is_tombstone) { is_tombstone_ = is_tombstone; }
     bool is_real () const { return is_used_ && !is_tombstone_; }
 
+    template <bool v = minus_one,
+	      hb_enable_if (v == false)>
+    static V default_value () { return V(); };
+    template <bool v = minus_one,
+	      hb_enable_if (v == true)>
+    static V default_value () { return V(-1); };
+
     void clear ()
     {
       new (std::addressof (key)) K ();
       new (std::addressof (value)) V ();
-      value = hb_coerce<V> (vINVALID);
+      value = default_value ();
       hash = 0;
       is_used_ = false;
       is_tombstone_ = false;
@@ -200,12 +204,12 @@ struct hb_hashmap_t
 
   V get (K key) const
   {
-    if (unlikely (!items)) return hb_coerce<V> (vINVALID);
+    if (unlikely (!items)) return item_t::default_value ();
     unsigned int i = bucket_for (key);
-    return items[i].is_real () && items[i] == key ? items[i].value : hb_coerce<V> (vINVALID);
+    return items[i].is_real () && items[i] == key ? items[i].value : item_t::default_value ();
   }
 
-  void del (K key) { set_with_hash (key, hb_hash (key), hb_coerce<V> (vINVALID), true); }
+  void del (K key) { set_with_hash (key, hb_hash (key), item_t::default_value (), true); }
 
   /* Has interface. */
   typedef V value_t;
@@ -214,8 +218,7 @@ struct hb_hashmap_t
   {
     const V &v = (*this)[k];
     if (vp) *vp = v;
-    const V vinv = hb_coerce<V> (vINVALID);
-    return v != vinv;
+    return v != item_t::default_value (); // TODO
   }
   /* Projection. */
   V operator () (K k) const { return get (k); }
@@ -398,13 +401,11 @@ struct hb_hashmap_t
 
 struct hb_map_t : hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID>
+			       true>
 {
   using hashmap = hb_hashmap_t<hb_codepoint_t,
 			       hb_codepoint_t,
-			       hb_codepoint_t,
-			       HB_MAP_VALUE_INVALID>;
+			       true>;
 
   ~hb_map_t () = default;
   hb_map_t () : hashmap () {}
diff --git a/src/hb-ot-post-table-v2subset.hh b/src/hb-ot-post-table-v2subset.hh
index 8c0312fa4..718b09d7e 100644
--- a/src/hb-ot-post-table-v2subset.hh
+++ b/src/hb-ot-post-table-v2subset.hh
@@ -78,7 +78,7 @@ HB_INTERNAL bool postV2Tail::subset (hb_subset_context_t *c) const
 
   post::accelerator_t _post (c->plan->source);
 
-  hb_hashmap_t<hb_bytes_t, unsigned> glyph_name_to_new_index;
+  hb_hashmap_t<hb_bytes_t, unsigned, true> glyph_name_to_new_index;
   for (hb_codepoint_t new_gid = 0; new_gid < num_glyphs; new_gid++)
   {
     hb_codepoint_t old_gid = reverse_glyph_map.get (new_gid);
diff --git a/src/hb-serialize.hh b/src/hb-serialize.hh
index 3f4535ce4..6f56faafe 100644
--- a/src/hb-serialize.hh
+++ b/src/hb-serialize.hh
@@ -719,8 +719,7 @@ struct hb_serialize_context_t
   hb_vector_t<object_t *> packed;
 
   /* Map view of packed objects. */
-  hb_hashmap_t<const object_t *, objidx_t,
-	       objidx_t, 0> packed_map;
+  hb_hashmap_t<const object_t *, objidx_t> packed_map;
 };
 
 #endif /* HB_SERIALIZE_HH */
diff --git a/src/test-map.cc b/src/test-map.cc
index e62f65091..0351d8161 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -27,11 +27,6 @@
 #include "hb-set.hh"
 #include <string>
 
-static const std::string invalid{"invalid"};
-static const hb_map_t invalid_map{};
-static const hb_set_t invalid_set{};
-static const hb_vector_t<unsigned> invalid_vector{};
-
 int
 main (int argc, char **argv)
 {
@@ -127,19 +122,19 @@ main (int argc, char **argv)
 
   /* Test class key / value types. */
   {
-    hb_hashmap_t<hb_bytes_t, int, int, 0> m1;
-    hb_hashmap_t<int, hb_bytes_t, std::nullptr_t, nullptr> m2;
-    hb_hashmap_t<hb_bytes_t, hb_bytes_t, std::nullptr_t, nullptr> m3;
+    hb_hashmap_t<hb_bytes_t, int> m1;
+    hb_hashmap_t<int, hb_bytes_t> m2;
+    hb_hashmap_t<hb_bytes_t, hb_bytes_t> m3;
     assert (m1.get_population () == 0);
     assert (m2.get_population () == 0);
     assert (m3.get_population () == 0);
   }
 
   {
-    hb_hashmap_t<int, int, int, 0> m0;
-    hb_hashmap_t<std::string, int, int, 0> m1;
-    hb_hashmap_t<int, std::string, const std::string*, &invalid> m2;
-    hb_hashmap_t<std::string, std::string, const std::string*, &invalid> m3;
+    hb_hashmap_t<int, int> m0;
+    hb_hashmap_t<std::string, int> m1;
+    hb_hashmap_t<int, std::string> m2;
+    hb_hashmap_t<std::string, std::string> m3;
 
     std::string s;
     for (unsigned i = 1; i < 1000; i++)
@@ -156,67 +151,49 @@ main (int argc, char **argv)
   {
     using pair = hb_pair_t<hb_codepoint_t, hb_codepoint_t>;
 
-    hb_hashmap_t<hb_map_t, hb_map_t, const hb_map_t *, &invalid_map> m1;
-    hb_hashmap_t<hb_map_t, hb_map_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<hb_map_t, hb_map_t> m1;
 
     m1.set (hb_map_t (), hb_map_t {});
-    m2.set (hb_map_t (), hb_map_t {});
 
     m1.set (hb_map_t (), hb_map_t {pair (1u, 2u)});
-    m2.set (hb_map_t (), hb_map_t {pair (1u, 2u)});
 
     m1.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
-    m2.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
 
     assert (m1.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
-    assert (m2.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
 
     assert (m1.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
-    assert (m2.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
   }
 
   /* Test hashing sets. */
   {
-    hb_hashmap_t<hb_set_t, hb_set_t, const hb_set_t *, &invalid_set> m1;
-    hb_hashmap_t<hb_set_t, hb_set_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<hb_set_t, hb_set_t> m1;
 
     m1.set (hb_set_t (), hb_set_t ());
-    m2.set (hb_set_t (), hb_set_t ());
 
     m1.set (hb_set_t (), hb_set_t {1});
-    m2.set (hb_set_t (), hb_set_t {1});
 
     m1.set (hb_set_t {1, 1000}, hb_set_t {2});
-    m2.set (hb_set_t {1, 1000}, hb_set_t {2});
 
     assert (m1.get (hb_set_t ()) == hb_set_t {1});
-    assert (m2.get (hb_set_t ()) == hb_set_t {1});
 
     assert (m1.get (hb_set_t {1000, 1}) == hb_set_t {2});
-    assert (m2.get (hb_set_t {1000, 1}) == hb_set_t {2});
   }
 
   /* Test hashing vectors. */
   {
     using vector_t = hb_vector_t<unsigned>;
 
-    hb_hashmap_t<vector_t, vector_t, const vector_t *, &invalid_vector> m1;
-    hb_hashmap_t<vector_t, vector_t, std::nullptr_t, nullptr> m2;
+    hb_hashmap_t<vector_t, vector_t> m1;
 
     m1.set (vector_t (), vector_t ());
-    m2.set (vector_t (), vector_t ());
 
     m1.set (vector_t (), vector_t {1});
-    m2.set (vector_t (), vector_t {1});
 
     m1.set (vector_t {1}, vector_t {2});
-    m2.set (vector_t {1}, vector_t {2});
 
     assert (m1.get (vector_t ()) == vector_t {1});
-    assert (m2.get (vector_t ()) == vector_t {1});
 
     assert (m1.get (vector_t {1}) == vector_t {2});
-    assert (m2.get (vector_t {1}) == vector_t {2});
   }
 
   /* Test hb::shared_ptr. */

From 97ea10a63a0be388bfb02ae203c468533304bda0 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:14:17 -0600
Subject: [PATCH 06/23] Remove old nullptr_t hacks

Were used for hashmap before.
---
 src/hb-array.hh | 2 --
 src/hb-map.hh   | 2 --
 src/hb-set.hh   | 1 -
 3 files changed, 5 deletions(-)

diff --git a/src/hb-array.hh b/src/hb-array.hh
index 1963698cf..5baeb6f7f 100644
--- a/src/hb-array.hh
+++ b/src/hb-array.hh
@@ -56,7 +56,6 @@ struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
   hb_array_t& operator= (const hb_array_t&) = default;
   hb_array_t& operator= (hb_array_t&&) = default;
 
-  constexpr hb_array_t (std::nullptr_t) : hb_array_t () {}
   constexpr hb_array_t (Type *array_, unsigned int length_) : arrayZ (array_), length (length_) {}
   template <unsigned int length_>
   constexpr hb_array_t (Type (&array_)[length_]) : hb_array_t (array_, length_) {}
@@ -314,7 +313,6 @@ struct hb_sorted_array_t :
   hb_sorted_array_t& operator= (const hb_sorted_array_t&) = default;
   hb_sorted_array_t& operator= (hb_sorted_array_t&&) = default;
 
-  constexpr hb_sorted_array_t (std::nullptr_t) : hb_sorted_array_t () {}
   constexpr hb_sorted_array_t (Type *array_, unsigned int length_) : hb_array_t<Type> (array_, length_) {}
   template <unsigned int length_>
   constexpr hb_sorted_array_t (Type (&array_)[length_]) : hb_array_t<Type> (array_) {}
diff --git a/src/hb-map.hh b/src/hb-map.hh
index 9b435c7d7..fb3d2d1c7 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -39,7 +39,6 @@ template <typename K, typename V,
 struct hb_hashmap_t
 {
   hb_hashmap_t ()  { init (); }
-  hb_hashmap_t (std::nullptr_t) : hb_hashmap_t () {}
   ~hb_hashmap_t () { fini (); }
 
   hb_hashmap_t (const hb_hashmap_t& o) : hb_hashmap_t () { resize (population); hb_copy (o, *this); }
@@ -409,7 +408,6 @@ struct hb_map_t : hb_hashmap_t<hb_codepoint_t,
 
   ~hb_map_t () = default;
   hb_map_t () : hashmap () {}
-  hb_map_t (std::nullptr_t) : hb_map_t () {}
   hb_map_t (const hb_map_t &o) : hashmap ((hashmap &) o) {}
   hb_map_t (hb_map_t &&o) : hashmap (std::move ((hashmap &) o)) {}
   hb_map_t& operator= (const hb_map_t&) = default;
diff --git a/src/hb-set.hh b/src/hb-set.hh
index 602562636..7eb5e19a2 100644
--- a/src/hb-set.hh
+++ b/src/hb-set.hh
@@ -166,7 +166,6 @@ struct hb_set_t : hb_sparseset_t<hb_bit_set_invertible_t>
 
   ~hb_set_t () = default;
   hb_set_t () : sparseset () {};
-  hb_set_t (std::nullptr_t) : hb_set_t () {};
   hb_set_t (const hb_set_t &o) : sparseset ((sparseset &) o) {};
   hb_set_t (hb_set_t&& o) : sparseset (std::move ((sparseset &) o)) {}
   hb_set_t& operator = (const hb_set_t&) = default;

From b9230c542558afac93f1fb6d7ca1442a06688d38 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:18:38 -0600
Subject: [PATCH 07/23] [map] Fix has()

---
 src/hb-map.hh | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index fb3d2d1c7..065ae1731 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -213,11 +213,24 @@ struct hb_hashmap_t
   /* Has interface. */
   typedef V value_t;
   value_t operator [] (K k) const { return get (k); }
-  bool has (K k, V *vp = nullptr) const
+  bool has (K key, V *vp = nullptr) const
   {
-    const V &v = (*this)[k];
-    if (vp) *vp = v;
-    return v != item_t::default_value (); // TODO
+    if (unlikely (!items))
+    {
+      if (vp) *vp = item_t::default_value ();
+      return false;
+    }
+    unsigned int i = bucket_for (key);
+    if (items[i].is_real () && items[i] == key)
+    {
+      if (vp) *vp = items[i].value;
+      return true;
+    }
+    else
+    {
+      if (vp) *vp = item_t::default_value ();
+      return false;
+    }
   }
   /* Projection. */
   V operator () (K k) const { return get (k); }

From 4c1b5d9ece8b59eb5346a8eaeaad09dfeb8dfd7f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:25:11 -0600
Subject: [PATCH 08/23] Whitespace

---
 src/test-map.cc | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/src/test-map.cc b/src/test-map.cc
index 0351d8161..65f11243f 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -154,13 +154,10 @@ main (int argc, char **argv)
     hb_hashmap_t<hb_map_t, hb_map_t> m1;
 
     m1.set (hb_map_t (), hb_map_t {});
-
     m1.set (hb_map_t (), hb_map_t {pair (1u, 2u)});
-
     m1.set (hb_map_t {pair (1u, 2u)}, hb_map_t {pair (2u, 3u)});
 
     assert (m1.get (hb_map_t ()) == hb_map_t {pair (1u, 2u)});
-
     assert (m1.get (hb_map_t {pair (1u, 2u)}) == hb_map_t {pair (2u, 3u)});
   }
 
@@ -169,13 +166,10 @@ main (int argc, char **argv)
     hb_hashmap_t<hb_set_t, hb_set_t> m1;
 
     m1.set (hb_set_t (), hb_set_t ());
-
     m1.set (hb_set_t (), hb_set_t {1});
-
     m1.set (hb_set_t {1, 1000}, hb_set_t {2});
 
     assert (m1.get (hb_set_t ()) == hb_set_t {1});
-
     assert (m1.get (hb_set_t {1000, 1}) == hb_set_t {2});
   }
 
@@ -186,13 +180,10 @@ main (int argc, char **argv)
     hb_hashmap_t<vector_t, vector_t> m1;
 
     m1.set (vector_t (), vector_t ());
-
     m1.set (vector_t (), vector_t {1});
-
     m1.set (vector_t {1}, vector_t {2});
 
     assert (m1.get (vector_t ()) == vector_t {1});
-
     assert (m1.get (vector_t {1}) == vector_t {2});
   }
 

From f0a0dcad703ca1db037687b4c59ce11668f38ca6 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:25:56 -0600
Subject: [PATCH 09/23] [test-map] Test hashing shared_ptr

---
 src/test-map.cc | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/test-map.cc b/src/test-map.cc
index 65f11243f..c4fdf45c1 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -189,14 +189,12 @@ main (int argc, char **argv)
 
   /* Test hb::shared_ptr. */
   hb_hash (hb::shared_ptr<hb_set_t> ());
-#if 0
   {
-    hb_hashmap_t<hb::shared_ptr<hb_set_t>, hb::shared_ptr<hb_set_t>, std::nullptr_t, std::nullptr_t, nullptr, nullptr> m;
+    hb_hashmap_t<hb::shared_ptr<hb_set_t>, hb::shared_ptr<hb_set_t>> m;
 
     m.get (hb::shared_ptr<hb_set_t> ());
     m.get (hb::shared_ptr<hb_set_t> (hb_set_get_empty ()));
   }
-#endif
 
   return 0;
 }

From a42a703cb62c84b2ed141e64570e1f1a2d74695e Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:51:20 -0600
Subject: [PATCH 10/23] [shared_ptr] Clear p in destructor

---
 src/hb-cplusplus.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-cplusplus.hh b/src/hb-cplusplus.hh
index afad2d1b8..76122523e 100644
--- a/src/hb-cplusplus.hh
+++ b/src/hb-cplusplus.hh
@@ -59,7 +59,7 @@ struct shared_ptr
   shared_ptr (shared_ptr &&o) : p (o.p) { o.p = nullptr; }
   shared_ptr& operator = (const shared_ptr &o) { if (p != o.p) { destroy (); p = o.p; reference (); } return *this; }
   shared_ptr& operator = (shared_ptr &&o) { destroy (); p = o.p; o.p = nullptr; return *this; }
-  ~shared_ptr () { v::destroy (p); }
+  ~shared_ptr () { v::destroy (p); p = nullptr; }
 
   T* get() const { return p; }
 

From e9407a2bd25f80d65559b6a869585033e2a08b24 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 11:29:44 -0600
Subject: [PATCH 11/23] Use shared_ptr<hb_set_t> in one place

See if valgrind is happy...
---
 src/hb-map.hh                |  2 +-
 src/hb-ot-layout-gsubgpos.hh |  9 +++------
 src/hb-ot-layout.cc          | 10 ++--------
 3 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 065ae1731..d3bb49a87 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -198,7 +198,7 @@ struct hb_hashmap_t
     return true;
   }
 
-  bool set (K key, const V& value) { return set_with_hash (key, hb_hash (key), value); }
+  bool set (K key, const V &value) { return set_with_hash (key, hb_hash (key), value); }
   bool set (K key, V&& value) { return set_with_hash (key, hb_hash (key), std::move (value)); }
 
   V get (K key) const
diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index fff5974d8..048278500 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -111,12 +111,9 @@ struct hb_closure_context_t :
 
       if (!done_lookups_glyph_set->get (lookup_index))
       {
-	hb_set_t* empty_set = hb_set_create ();
+	hb::shared_ptr<hb_set_t> empty_set {hb_set_create ()};
 	if (unlikely (!done_lookups_glyph_set->set (lookup_index, empty_set)))
-	{
-	  hb_set_destroy (empty_set);
 	  return true;
-	}
       }
 
       hb_set_clear (done_lookups_glyph_set->get (lookup_index));
@@ -171,7 +168,7 @@ struct hb_closure_context_t :
   hb_closure_context_t (hb_face_t *face_,
 			hb_set_t *glyphs_,
 			hb_map_t *done_lookups_glyph_count_,
-			hb_hashmap_t<unsigned, hb_set_t *> *done_lookups_glyph_set_,
+			hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *done_lookups_glyph_set_,
 			unsigned int nesting_level_left_ = HB_MAX_NESTING_LEVEL) :
 			  face (face_),
 			  glyphs (glyphs_),
@@ -195,7 +192,7 @@ struct hb_closure_context_t :
 
   private:
   hb_map_t *done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb_set_t *> *done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *done_lookups_glyph_set;
   unsigned int lookup_count = 0;
 };
 
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 9a8070a4a..f5031be81 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1501,15 +1501,12 @@ hb_ot_layout_lookup_substitute_closure (hb_face_t    *face,
 					hb_set_t     *glyphs /* OUT */)
 {
   hb_map_t done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb_set_t *> done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> done_lookups_glyph_set;
   OT::hb_closure_context_t c (face, glyphs, &done_lookups_glyph_count, &done_lookups_glyph_set);
 
   const OT::SubstLookup& l = face->table.GSUB->table->get_lookup (lookup_index);
 
   l.closure (&c, lookup_index);
-
-  for (auto _ : done_lookups_glyph_set.iter ())
-    hb_set_destroy (_.second);
 }
 
 /**
@@ -1529,7 +1526,7 @@ hb_ot_layout_lookups_substitute_closure (hb_face_t      *face,
 					 hb_set_t       *glyphs /* OUT */)
 {
   hb_map_t done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb_set_t *> done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> done_lookups_glyph_set;
   OT::hb_closure_context_t c (face, glyphs, &done_lookups_glyph_count, &done_lookups_glyph_set);
   const GSUB& gsub = *face->table.GSUB->table;
 
@@ -1551,9 +1548,6 @@ hb_ot_layout_lookups_substitute_closure (hb_face_t      *face,
     }
   } while (iteration_count++ <= HB_CLOSURE_MAX_STAGES &&
 	   glyphs_length != glyphs->get_population ());
-
-  for (auto _ : done_lookups_glyph_set.iter ())
-    hb_set_destroy (_.second);
 }
 
 /*

From bca710e8ad2cccaa013e19a63c58899e45284df8 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 12:06:25 -0600
Subject: [PATCH 12/23] [gsubgpos] Use map has() instead of get() when
 appropriate

---
 src/hb-ot-layout-gsubgpos.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 048278500..276a3601c 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -109,7 +109,7 @@ struct hb_closure_context_t :
     {
       done_lookups_glyph_count->set (lookup_index, glyphs->get_population ());
 
-      if (!done_lookups_glyph_set->get (lookup_index))
+      if (!done_lookups_glyph_set->has (lookup_index))
       {
 	hb::shared_ptr<hb_set_t> empty_set {hb_set_create ()};
 	if (unlikely (!done_lookups_glyph_set->set (lookup_index, empty_set)))

From d7785a6da0a5ced69203270a48a9a4da9e8f230a Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 12:42:24 -0600
Subject: [PATCH 13/23] [cplusplus] Add unique_ptr

---
 src/hb-algs.hh             |  5 +++++
 src/hb-cplusplus.hh        | 44 +++++++++++++++++++++++++++++++++++++-
 test/api/test-cplusplus.cc |  2 ++
 3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index 34e512e7e..ce4849b01 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -247,6 +247,11 @@ struct
   {
     return v.get () ? v.get ()->hash () : 0;
   }
+  template <typename T> constexpr uint32_t
+  impl (const hb::unique_ptr<T>& v, hb_priority<1>) const
+  {
+    return v.get () ? v.get ()->hash () : 0;
+  }
 
   template <typename T> constexpr auto
   impl (const T& v, hb_priority<0>) const HB_RETURN (uint32_t, std::hash<hb_decay<decltype (hb_deref (v))>>{} (hb_deref (v)))
diff --git a/src/hb-cplusplus.hh b/src/hb-cplusplus.hh
index 76122523e..86d045208 100644
--- a/src/hb-cplusplus.hh
+++ b/src/hb-cplusplus.hh
@@ -58,7 +58,7 @@ struct shared_ptr
   shared_ptr (const shared_ptr &o) : p (v::reference (o.p)) {}
   shared_ptr (shared_ptr &&o) : p (o.p) { o.p = nullptr; }
   shared_ptr& operator = (const shared_ptr &o) { if (p != o.p) { destroy (); p = o.p; reference (); } return *this; }
-  shared_ptr& operator = (shared_ptr &&o) { destroy (); p = o.p; o.p = nullptr; return *this; }
+  shared_ptr& operator = (shared_ptr &&o) { v::destroy (p); p = o.p; o.p = nullptr; return *this; }
   ~shared_ptr () { v::destroy (p); p = nullptr; }
 
   T* get() const { return p; }
@@ -89,6 +89,38 @@ struct shared_ptr
 template<typename T> struct is_shared_ptr : std::false_type {};
 template<typename T> struct is_shared_ptr<shared_ptr<T>> : std::true_type {};
 
+template <typename T>
+struct unique_ptr
+{
+  using element_type = T;
+
+  using v = vtable<T>;
+
+  explicit unique_ptr (T *p = nullptr) : p (p) {}
+  unique_ptr (const unique_ptr &o) = delete;
+  unique_ptr (unique_ptr &&o) : p (o.p) { o.p = nullptr; }
+  unique_ptr& operator = (const unique_ptr &o) = delete;
+  unique_ptr& operator = (unique_ptr &&o) { v::destroy (p); p = o.p; o.p = nullptr; return *this; }
+  ~unique_ptr () { v::destroy (p); p = nullptr; }
+
+  T* get() const { return p; }
+  T* release () { T* v = p; p = nullptr; return v; }
+
+  void swap (unique_ptr &o) { std::swap (p, o.p); }
+  friend void swap (unique_ptr &a, unique_ptr &b) { std::swap (a.p, b.p); }
+
+  operator T * () const { return p; }
+  T& operator * () const { return *get (); }
+  T* operator -> () const { return get (); }
+  operator bool () { return p; }
+
+  private:
+  T *p;
+};
+
+template<typename T> struct is_unique_ptr : std::false_type {};
+template<typename T> struct is_unique_ptr<unique_ptr<T>> : std::true_type {};
+
 template <typename T,
 	  T * (*_get_empty) (void),
 	  T * (*_reference) (T *),
@@ -144,6 +176,16 @@ struct std::hash<hb::shared_ptr<T>>
     }
 };
 
+template<typename T>
+struct std::hash<hb::unique_ptr<T>>
+{
+    std::size_t operator()(const hb::unique_ptr<T>& v) const noexcept
+    {
+        std::size_t h = std::hash<decltype (v.get ())>{}(v.get ());
+        return h;
+    }
+};
+
 
 #endif /* __cplusplus */
 
diff --git a/test/api/test-cplusplus.cc b/test/api/test-cplusplus.cc
index d23e794c4..d742750f6 100644
--- a/test/api/test-cplusplus.cc
+++ b/test/api/test-cplusplus.cc
@@ -106,5 +106,7 @@ main ()
   pb.set_user_data (&key, b, nullptr, true);
   (void) pb.get_user_data (&key);
 
+  hb::unique_ptr<hb_buffer_t> pb5 {pb3.reference ()};
+
   return pb == pb.get_empty () || pb == pb2;
 }

From 8bb2a3326e92d553b9bea7462574a2d44782cbfd Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 15:18:23 -0600
Subject: [PATCH 14/23] [map] Remove unneeded assignment

---
 src/hb-map.hh | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index d3bb49a87..262954c34 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -86,7 +86,6 @@ struct hb_hashmap_t
     {
       new (std::addressof (key)) K ();
       new (std::addressof (value)) V ();
-      value = default_value ();
       hash = 0;
       is_used_ = false;
       is_tombstone_ = false;

From 997d9cc466abfb9031f46d1baef5a2cb3164f7cc Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 18:04:12 -0600
Subject: [PATCH 15/23] [map] Make unique_ptr hashable

---
 src/hb-bimap.hh                  |  3 ++-
 src/hb-map.hh                    | 24 ++++++++++++------------
 src/hb-ot-color-cpal-table.hh    |  4 ++--
 src/hb-ot-layout-common.hh       |  4 ++--
 src/hb-ot-layout-gsubgpos.hh     |  7 +++----
 src/hb-ot-layout.cc              |  4 ++--
 src/hb-ot-post-table-v2subset.hh |  4 +++-
 src/hb-repacker.hh               | 16 ++++++++--------
 src/test-map.cc                  |  8 ++++++++
 9 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/src/hb-bimap.hh b/src/hb-bimap.hh
index 8ce4a5e80..8e8c98871 100644
--- a/src/hb-bimap.hh
+++ b/src/hb-bimap.hh
@@ -64,7 +64,8 @@ struct hb_bimap_t
   hb_codepoint_t backward (hb_codepoint_t rhs) const { return back_map.get (rhs); }
 
   hb_codepoint_t operator [] (hb_codepoint_t lhs) const { return get (lhs); }
-  bool has (hb_codepoint_t lhs, hb_codepoint_t *vp = nullptr) const { return forw_map.has (lhs, vp); }
+  bool has (hb_codepoint_t lhs) const { return forw_map.has (lhs); }
+
 
   void del (hb_codepoint_t lhs)
   {
diff --git a/src/hb-map.hh b/src/hb-map.hh
index 262954c34..028e4654b 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -77,10 +77,10 @@ struct hb_hashmap_t
 
     template <bool v = minus_one,
 	      hb_enable_if (v == false)>
-    static V default_value () { return V(); };
+    static const V& default_value () { return Null(V); };
     template <bool v = minus_one,
 	      hb_enable_if (v == true)>
-    static V default_value () { return V(-1); };
+    static const V& default_value () { static const V minus_1 = -1; return minus_1; };
 
     void clear ()
     {
@@ -197,10 +197,10 @@ struct hb_hashmap_t
     return true;
   }
 
-  bool set (K key, const V &value) { return set_with_hash (key, hb_hash (key), value); }
-  bool set (K key, V&& value) { return set_with_hash (key, hb_hash (key), std::move (value)); }
+  template <typename VV>
+  bool set (K key, VV&& value) { return set_with_hash (key, hb_hash (key), std::forward<VV> (value)); }
 
-  V get (K key) const
+  const V& get (K key) const
   {
     if (unlikely (!items)) return item_t::default_value ();
     unsigned int i = bucket_for (key);
@@ -212,22 +212,22 @@ struct hb_hashmap_t
   /* Has interface. */
   typedef V value_t;
   value_t operator [] (K k) const { return get (k); }
-  bool has (K key, V *vp = nullptr) const
+  bool has (K key, const V **vp = nullptr) const
   {
     if (unlikely (!items))
     {
-      if (vp) *vp = item_t::default_value ();
+      if (vp) *vp = &item_t::default_value ();
       return false;
     }
     unsigned int i = bucket_for (key);
     if (items[i].is_real () && items[i] == key)
     {
-      if (vp) *vp = items[i].value;
+      if (vp) *vp = &items[i].value;
       return true;
     }
     else
     {
-      if (vp) *vp = item_t::default_value ();
+      if (vp) *vp = &item_t::default_value ();
       return false;
     }
   }
@@ -320,7 +320,7 @@ struct hb_hashmap_t
     }
 
     items[i].key = key;
-    items[i].value = value;
+    items[i].value = std::forward<VV> (value);
     items[i].hash = hash;
     items[i].set_used (true);
     items[i].set_tombstone (is_delete);
@@ -332,12 +332,12 @@ struct hb_hashmap_t
     return true;
   }
 
-  unsigned int bucket_for (K key) const
+  unsigned int bucket_for (const K &key) const
   {
     return bucket_for_hash (key, hb_hash (key));
   }
 
-  unsigned int bucket_for_hash (K key, uint32_t hash) const
+  unsigned int bucket_for_hash (const K &key, uint32_t hash) const
   {
     hash &= 0x3FFFFFFF; // We only store lower 30bit of hash
     unsigned int i = hash % prime;
diff --git a/src/hb-ot-color-cpal-table.hh b/src/hb-ot-color-cpal-table.hh
index 201fa3e46..bcab77f79 100644
--- a/src/hb-ot-color-cpal-table.hh
+++ b/src/hb-ot-color-cpal-table.hh
@@ -97,10 +97,10 @@ struct CPALV1Tail
       c->push ();
       for (const auto _ : colorLabels)
       {
-	hb_codepoint_t v;
+	const hb_codepoint_t *v;
         if (!color_index_map->has (_, &v)) continue;
         NameID new_color_idx;
-	new_color_idx = v;
+	new_color_idx = *v;
         if (!c->copy<NameID> (new_color_idx))
         {
           c->pop_discard ();
diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index f9a11657d..a195363d7 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -659,8 +659,8 @@ struct LangSys
     auto *out = c->serializer->start_embed (*this);
     if (unlikely (!out || !c->serializer->extend_min (out))) return_trace (false);
 
-    unsigned v;
-    out->reqFeatureIndex = l->feature_index_map->has (reqFeatureIndex, &v) ? v : 0xFFFFu;
+    const unsigned *v;
+    out->reqFeatureIndex = l->feature_index_map->has (reqFeatureIndex, &v) ? *v : 0xFFFFu;
 
     if (!l->visitFeatureIndex (featureIndex.len))
       return_trace (false);
diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 276a3601c..b76b43139 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -111,8 +111,7 @@ struct hb_closure_context_t :
 
       if (!done_lookups_glyph_set->has (lookup_index))
       {
-	hb::shared_ptr<hb_set_t> empty_set {hb_set_create ()};
-	if (unlikely (!done_lookups_glyph_set->set (lookup_index, empty_set)))
+	if (unlikely (!done_lookups_glyph_set->set (lookup_index, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
 	  return true;
       }
 
@@ -168,7 +167,7 @@ struct hb_closure_context_t :
   hb_closure_context_t (hb_face_t *face_,
 			hb_set_t *glyphs_,
 			hb_map_t *done_lookups_glyph_count_,
-			hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *done_lookups_glyph_set_,
+			hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *done_lookups_glyph_set_,
 			unsigned int nesting_level_left_ = HB_MAX_NESTING_LEVEL) :
 			  face (face_),
 			  glyphs (glyphs_),
@@ -192,7 +191,7 @@ struct hb_closure_context_t :
 
   private:
   hb_map_t *done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> *done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *done_lookups_glyph_set;
   unsigned int lookup_count = 0;
 };
 
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index f5031be81..35e887ba3 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1501,7 +1501,7 @@ hb_ot_layout_lookup_substitute_closure (hb_face_t    *face,
 					hb_set_t     *glyphs /* OUT */)
 {
   hb_map_t done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> done_lookups_glyph_set;
   OT::hb_closure_context_t c (face, glyphs, &done_lookups_glyph_count, &done_lookups_glyph_set);
 
   const OT::SubstLookup& l = face->table.GSUB->table->get_lookup (lookup_index);
@@ -1526,7 +1526,7 @@ hb_ot_layout_lookups_substitute_closure (hb_face_t      *face,
 					 hb_set_t       *glyphs /* OUT */)
 {
   hb_map_t done_lookups_glyph_count;
-  hb_hashmap_t<unsigned, hb::shared_ptr<hb_set_t>> done_lookups_glyph_set;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> done_lookups_glyph_set;
   OT::hb_closure_context_t c (face, glyphs, &done_lookups_glyph_count, &done_lookups_glyph_set);
   const GSUB& gsub = *face->table.GSUB->table;
 
diff --git a/src/hb-ot-post-table-v2subset.hh b/src/hb-ot-post-table-v2subset.hh
index 718b09d7e..c8a4429eb 100644
--- a/src/hb-ot-post-table-v2subset.hh
+++ b/src/hb-ot-post-table-v2subset.hh
@@ -85,9 +85,11 @@ HB_INTERNAL bool postV2Tail::subset (hb_subset_context_t *c) const
     unsigned old_index = glyphNameIndex[old_gid];
 
     unsigned new_index;
+    const unsigned *new_index2;
     if (old_index <= 257) new_index = old_index;
-    else if (!old_new_index_map.has (old_index, &new_index))
+    else if (!old_new_index_map.has (old_index, &new_index2))
     {
+      new_index = *new_index2;
       hb_bytes_t s = _post.find_glyph_name (old_gid);
       new_index = glyph_name_to_new_index.get (s);
       if (new_index == (unsigned)-1)
diff --git a/src/hb-repacker.hh b/src/hb-repacker.hh
index 66dce8df8..c9075fa1e 100644
--- a/src/hb-repacker.hh
+++ b/src/hb-repacker.hh
@@ -430,8 +430,8 @@ struct graph_t
     auto new_subgraph =
         + subgraph.keys ()
         | hb_map([&] (unsigned node_idx) {
-	  unsigned v;
-          if (index_map.has (node_idx, &v)) return v;
+	  const unsigned *v;
+          if (index_map.has (node_idx, &v)) return *v;
           return node_idx;
         })
         ;
@@ -443,11 +443,11 @@ struct graph_t
     unsigned next = HB_SET_VALUE_INVALID;
     while (roots.next (&next))
     {
-      unsigned v;
+      const unsigned *v;
       if (index_map.has (next, &v))
       {
         roots.del (next);
-        roots.add (v);
+        roots.add (*v);
       }
     }
 
@@ -458,10 +458,10 @@ struct graph_t
   {
     for (const auto& link : vertices_[node_idx].obj.all_links ())
     {
-      unsigned v;
+      const unsigned *v;
       if (subgraph.has (link.objidx, &v))
       {
-        subgraph.set (link.objidx, v + 1);
+        subgraph.set (link.objidx, *v + 1);
         continue;
       }
       subgraph.set (link.objidx, 1);
@@ -943,11 +943,11 @@ struct graph_t
     {
       for (auto& link : vertices_[i].obj.all_links_writer ())
       {
-	unsigned v;
+	const unsigned *v;
         if (!id_map.has (link.objidx, &v)) continue;
         if (only_wide && !(link.width == 4 && !link.is_signed)) continue;
 
-        reassign_link (link, i, v);
+        reassign_link (link, i, *v);
       }
     }
   }
diff --git a/src/test-map.cc b/src/test-map.cc
index c4fdf45c1..9eef49e88 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -195,6 +195,14 @@ main (int argc, char **argv)
     m.get (hb::shared_ptr<hb_set_t> ());
     m.get (hb::shared_ptr<hb_set_t> (hb_set_get_empty ()));
   }
+  /* Test hb::unique_ptr. */
+  hb_hash (hb::unique_ptr<hb_set_t> ());
+  {
+    hb_hashmap_t<hb::unique_ptr<hb_set_t>, hb::unique_ptr<hb_set_t>> m;
+
+    m.get (hb::unique_ptr<hb_set_t> ());
+    m.get (hb::unique_ptr<hb_set_t> (hb_set_get_empty ()));
+  }
 
   return 0;
 }

From a7a688616ab348a66873df5577eec66a0f70206f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 2 Jun 2022 18:59:15 -0600
Subject: [PATCH 16/23] [cmap] Convert another map use to unique_ptr

---
 src/hb-ot-cmap-table.hh | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index 7e96d9c8b..9d95f518c 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -1476,26 +1476,17 @@ struct SubtableUnicodesCache {
 
  private:
   const void* base;
-  hb_hashmap_t<intptr_t, hb_set_t*> cached_unicodes;
+  hb_hashmap_t<intptr_t, hb::unique_ptr<hb_set_t>> cached_unicodes;
 
  public:
   SubtableUnicodesCache(const void* cmap_base)
       : base(cmap_base), cached_unicodes() {}
-  ~SubtableUnicodesCache()
-  {
-    for (hb_set_t* s : cached_unicodes.values()) {
-      hb_set_destroy (s);
-    }
-  }
 
   hb_set_t* set_for(const EncodingRecord* record)
   {
     if (!cached_unicodes.has ((intptr_t) record)) {
-      hb_set_t* new_set = hb_set_create ();
-      if (!cached_unicodes.set ((intptr_t) record, new_set)) {
-        hb_set_destroy (new_set);
+      if (!cached_unicodes.set ((intptr_t) record, hb::unique_ptr<hb_set_t> {hb_set_create ()}))
         return hb_set_get_empty ();
-      }
       (base+record->subtable).collect_unicodes (cached_unicodes.get ((intptr_t) record));
     }
     return cached_unicodes.get ((intptr_t) record);

From 25f57230d58524d9165a9b33d1666f84005617d5 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:11:22 -0600
Subject: [PATCH 17/23] [map] Return references from new iter_ref()

---
 src/hb-map.hh | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index 028e4654b..f91da642d 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -94,6 +94,7 @@ struct hb_hashmap_t
     bool operator == (const K &o) { return hb_deref (key) == hb_deref (o); }
     bool operator == (const item_t &o) { return *this == o.key; }
     hb_pair_t<K, V> get_pair() const { return hb_pair_t<K, V> (key, value); }
+    hb_pair_t<const K &, const V &> get_pair_ref() const { return hb_pair_t<const K, const V &> (key, value); }
 
     uint32_t total_hash () const
     { return (hash * 31) + hb_hash (value); }
@@ -281,6 +282,12 @@ struct hb_hashmap_t
     | hb_filter (&item_t::is_real)
     | hb_map (&item_t::get_pair)
   )
+  auto iter_ref () const HB_AUTO_RETURN
+  (
+    + hb_array (items, mask ? mask + 1 : 0)
+    | hb_filter (&item_t::is_real)
+    | hb_map (&item_t::get_pair)
+  )
   auto keys () const HB_AUTO_RETURN
   (
     + hb_array (items, mask ? mask + 1 : 0)

From f13a79548fca34663ec3f0f86de6f2e742a09ab9 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:17:20 -0600
Subject: [PATCH 18/23] [subset] Convert another use of hashmap to unique_ptr

---
 src/hb-ot-layout-common.hh   | 14 +++++---------
 src/hb-ot-layout-gsubgpos.hh |  2 +-
 src/hb-subset-plan.cc        |  8 +-------
 src/hb-subset-plan.hh        |  4 ++--
 4 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index a195363d7..015180778 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -102,7 +102,7 @@ static void ClassDef_remap_and_serialize (
 struct hb_prune_langsys_context_t
 {
   hb_prune_langsys_context_t (const void         *table_,
-                              hb_hashmap_t<unsigned, hb_set_t *> *script_langsys_map_,
+                              hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map_,
                               const hb_map_t     *duplicate_feature_map_,
                               hb_set_t           *new_collected_feature_indexes_)
       :table (table_),
@@ -122,7 +122,7 @@ struct hb_prune_langsys_context_t
 
   public:
   const void *table;
-  hb_hashmap_t<unsigned, hb_set_t *> *script_langsys_map;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map;
   const hb_map_t     *duplicate_feature_map;
   hb_set_t           *new_feature_indexes;
 
@@ -162,14 +162,14 @@ struct hb_subset_layout_context_t :
   hb_subset_context_t *subset_context;
   const hb_tag_t table_tag;
   const hb_map_t *lookup_index_map;
-  const hb_hashmap_t<unsigned, hb_set_t *> *script_langsys_map;
+  const hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map;
   const hb_map_t *feature_index_map;
   unsigned cur_script_index;
 
   hb_subset_layout_context_t (hb_subset_context_t *c_,
 			      hb_tag_t tag_,
 			      hb_map_t *lookup_map_,
-			      hb_hashmap_t<unsigned, hb_set_t *> *script_langsys_map_,
+			      hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map_,
 			      hb_map_t *feature_index_map_) :
 				subset_context (c_),
 				table_tag (tag_),
@@ -723,12 +723,8 @@ struct Script
 
     if (!c->script_langsys_map->has (script_index))
     {
-      hb_set_t* empty_set = hb_set_create ();
-      if (unlikely (!c->script_langsys_map->set (script_index, empty_set)))
-      {
-	hb_set_destroy (empty_set);
+      if (unlikely (!c->script_langsys_map->set (script_index, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
 	return;
-      }
     }
 
     unsigned langsys_count = get_lang_sys_count ();
diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index b76b43139..63f729c85 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -3729,7 +3729,7 @@ struct GSUBGPOS
   }
 
   void prune_langsys (const hb_map_t *duplicate_feature_map,
-                      hb_hashmap_t<unsigned, hb_set_t *> *script_langsys_map,
+                      hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *script_langsys_map,
                       hb_set_t       *new_feature_indexes /* OUT */) const
   {
     hb_prune_langsys_context_t c (this, script_langsys_map, duplicate_feature_map, new_feature_indexes);
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index a62ae8e02..5bfa2d096 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -43,7 +43,7 @@
 using OT::Layout::GSUB::GSUB;
 
 
-typedef hb_hashmap_t<unsigned, hb_set_t *> script_langsys_map;
+typedef hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> script_langsys_map;
 #ifndef HB_NO_SUBSET_CFF
 static inline void
 _add_cff_seac_components (const OT::cff1::accelerator_t &cff,
@@ -630,9 +630,6 @@ hb_subset_plan_destroy (hb_subset_plan_t *plan)
 
   if (plan->gsub_langsys)
   {
-    for (auto _ : plan->gsub_langsys->iter ())
-      hb_set_destroy (_.second);
-
     hb_object_destroy (plan->gsub_langsys);
     plan->gsub_langsys->fini_shallow ();
     hb_free (plan->gsub_langsys);
@@ -640,9 +637,6 @@ hb_subset_plan_destroy (hb_subset_plan_t *plan)
 
   if (plan->gpos_langsys)
   {
-    for (auto _ : plan->gpos_langsys->iter ())
-      hb_set_destroy (_.second);
-
     hb_object_destroy (plan->gpos_langsys);
     plan->gpos_langsys->fini_shallow ();
     hb_free (plan->gpos_langsys);
diff --git a/src/hb-subset-plan.hh b/src/hb-subset-plan.hh
index cb567b769..2aaf19c61 100644
--- a/src/hb-subset-plan.hh
+++ b/src/hb-subset-plan.hh
@@ -87,8 +87,8 @@ struct hb_subset_plan_t
   hb_map_t *gpos_lookups;
 
   //active langsys we'd like to retain
-  hb_hashmap_t<unsigned, hb_set_t *> *gsub_langsys;
-  hb_hashmap_t<unsigned, hb_set_t *> *gpos_langsys;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *gsub_langsys;
+  hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> *gpos_langsys;
 
   //active features after removing redundant langsys and prune_features
   hb_map_t *gsub_features;

From a42c624fcaa030a68c51acaf007caf402c8c262c Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:22:34 -0600
Subject: [PATCH 19/23] Convert one final use of hashmap to unique_ptr

---
 src/hb-ot-layout-gsubgpos.hh | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 63f729c85..a93d5436d 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -3787,7 +3787,7 @@ struct GSUBGPOS
                                 hb_map_t *duplicate_feature_map /* OUT */) const
   {
     if (feature_indices->is_empty ()) return;
-    hb_hashmap_t<hb_tag_t, hb_set_t *> unique_features;
+    hb_hashmap_t<hb_tag_t, hb::unique_ptr<hb_set_t>> unique_features;
     //find out duplicate features after subset
     for (unsigned i : feature_indices->iter ())
     {
@@ -3795,16 +3795,9 @@ struct GSUBGPOS
       if (t == HB_MAP_VALUE_INVALID) continue;
       if (!unique_features.has (t))
       {
-        hb_set_t* indices = hb_set_create ();
-        if (unlikely (indices == hb_set_get_empty () ||
-                      !unique_features.set (t, indices)))
-        {
-          hb_set_destroy (indices);
-          for (auto _ : unique_features.iter ())
-            hb_set_destroy (_.second);
+        if (unlikely (!unique_features.set (t, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
           return;
-        }
-        if (unique_features.get (t))
+        if (unique_features.has (t))
           unique_features.get (t)->add (i);
         duplicate_feature_map->set (i, i);
         continue;
@@ -3849,9 +3842,6 @@ struct GSUBGPOS
         duplicate_feature_map->set (i, i);
       }
     }
-
-    for (auto _ : unique_features.iter ())
-      hb_set_destroy (_.second);
   }
 
   void prune_features (const hb_map_t *lookup_indices, /* IN */

From 88f00ecb84a5f78dffabdfa5a8bdc2ed1d452ce4 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:30:27 -0600
Subject: [PATCH 20/23] [map] Fix iter_ref () and test it

---
 src/hb-map.hh   | 4 ++--
 src/test-map.cc | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/hb-map.hh b/src/hb-map.hh
index f91da642d..cc423c3ef 100644
--- a/src/hb-map.hh
+++ b/src/hb-map.hh
@@ -94,7 +94,7 @@ struct hb_hashmap_t
     bool operator == (const K &o) { return hb_deref (key) == hb_deref (o); }
     bool operator == (const item_t &o) { return *this == o.key; }
     hb_pair_t<K, V> get_pair() const { return hb_pair_t<K, V> (key, value); }
-    hb_pair_t<const K &, const V &> get_pair_ref() const { return hb_pair_t<const K, const V &> (key, value); }
+    hb_pair_t<const K &, const V &> get_pair_ref() const { return hb_pair_t<const K &, const V &> (key, value); }
 
     uint32_t total_hash () const
     { return (hash * 31) + hb_hash (value); }
@@ -286,7 +286,7 @@ struct hb_hashmap_t
   (
     + hb_array (items, mask ? mask + 1 : 0)
     | hb_filter (&item_t::is_real)
-    | hb_map (&item_t::get_pair)
+    | hb_map (&item_t::get_pair_ref)
   )
   auto keys () const HB_AUTO_RETURN
   (
diff --git a/src/test-map.cc b/src/test-map.cc
index 9eef49e88..4cb248bd4 100644
--- a/src/test-map.cc
+++ b/src/test-map.cc
@@ -194,6 +194,7 @@ main (int argc, char **argv)
 
     m.get (hb::shared_ptr<hb_set_t> ());
     m.get (hb::shared_ptr<hb_set_t> (hb_set_get_empty ()));
+    m.iter ();
   }
   /* Test hb::unique_ptr. */
   hb_hash (hb::unique_ptr<hb_set_t> ());
@@ -202,6 +203,7 @@ main (int argc, char **argv)
 
     m.get (hb::unique_ptr<hb_set_t> ());
     m.get (hb::unique_ptr<hb_set_t> (hb_set_get_empty ()));
+    m.iter_ref ();
   }
 
   return 0;

From 9552955e081f3d871765055fd5abad9070cfcf90 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:33:01 -0600
Subject: [PATCH 21/23] Add an unlikely

---
 src/hb-ot-cmap-table.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index 9d95f518c..24d548a2a 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -1485,7 +1485,7 @@ struct SubtableUnicodesCache {
   hb_set_t* set_for(const EncodingRecord* record)
   {
     if (!cached_unicodes.has ((intptr_t) record)) {
-      if (!cached_unicodes.set ((intptr_t) record, hb::unique_ptr<hb_set_t> {hb_set_create ()}))
+      if (unlikely (!cached_unicodes.set ((intptr_t) record, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
         return hb_set_get_empty ();
       (base+record->subtable).collect_unicodes (cached_unicodes.get ((intptr_t) record));
     }

From 5dc12d7d8d7aeb3418870d2b3695ff10a53296f6 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:37:02 -0600
Subject: [PATCH 22/23] [cmap] Rewrite set_for() slightly

---
 src/hb-ot-cmap-table.hh | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index 24d548a2a..4fd2b9be4 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -1482,12 +1482,20 @@ struct SubtableUnicodesCache {
   SubtableUnicodesCache(const void* cmap_base)
       : base(cmap_base), cached_unicodes() {}
 
-  hb_set_t* set_for(const EncodingRecord* record)
+  hb_set_t* set_for (const EncodingRecord* record)
   {
-    if (!cached_unicodes.has ((intptr_t) record)) {
-      if (unlikely (!cached_unicodes.set ((intptr_t) record, hb::unique_ptr<hb_set_t> {hb_set_create ()})))
+    if (!cached_unicodes.has ((intptr_t) record))
+    {
+      hb_set_t *s = hb_set_create ();
+      if (unlikely (s->in_error ()))
+	return hb_set_get_empty ();
+	
+      (base+record->subtable).collect_unicodes (s);
+
+      if (unlikely (!cached_unicodes.set ((intptr_t) record, hb::unique_ptr<hb_set_t> {s})))
         return hb_set_get_empty ();
-      (base+record->subtable).collect_unicodes (cached_unicodes.get ((intptr_t) record));
+
+      return s;
     }
     return cached_unicodes.get ((intptr_t) record);
   }

From 215a0afad19a43f88cb8fbeb51877997b40e2567 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 3 Jun 2022 01:48:46 -0600
Subject: [PATCH 23/23] [algs] Remove unused hb_coerce()

---
 src/hb-algs.hh | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index ce4849b01..0f08d5070 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -227,14 +227,6 @@ struct
 }
 HB_FUNCOBJ (hb_bool);
 
-template <typename T>
-static inline
-constexpr T hb_coerce (const T v) { return v; }
-template <typename T, typename V,
-	  hb_enable_if (!hb_is_same (hb_decay<T>, hb_decay<V>) && std::is_pointer<V>::value)>
-static inline
-constexpr T hb_coerce (const V v) { return *v; }
-
 struct
 {
   private: