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] [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;
 }