From d3976b7e63559b87ef34abc62acf5033f3369197 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 26 Dec 2018 18:54:27 -0500
Subject: [PATCH] [iter] Make them work, mostly

---
 src/hb-iter.hh   | 11 ++++++++---
 src/hb-set.hh    | 18 ++++++++++--------
 src/test-iter.cc | 25 +++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/src/hb-iter.hh b/src/hb-iter.hh
index c83ccb39b..60b3b6503 100644
--- a/src/hb-iter.hh
+++ b/src/hb-iter.hh
@@ -65,9 +65,9 @@ struct hb_iter_t
   iter_t& operator ++ () { next (); return *thiz(); }
   iter_t& operator -= (unsigned count) { rewind (count); return *thiz(); }
   iter_t& operator -- () { prev (); return *thiz(); }
-  iter_t operator + (unsigned count) { iter_t c (*thiz()); c += count; return c; }
+  iter_t operator + (unsigned count) const { iter_t c (*thiz()); c += count; return c; }
   iter_t operator ++ (int) { iter_t c (*thiz()); ++*thiz(); return c; }
-  iter_t operator - (unsigned count) { iter_t c (*thiz()); c -= count; return c; }
+  iter_t operator - (unsigned count) const { iter_t c (*thiz()); c -= count; return c; }
   iter_t operator -- (int) { iter_t c (*thiz()); --*thiz(); return c; }
 
   /* Methods. */
@@ -112,7 +112,7 @@ struct hb_iter_mixin_t
 
   /* Access: Implement __item__(), or __item_at__() if random-access. */
   item_t& __item__ () const { return thiz()->item_at (0); }
-  item_t& __item_at__ (unsigned i) const { return *(thiz() + i); }
+  item_t& __item_at__ (unsigned i) const { return *(*thiz() + i); }
 
   /* Termination: Implement __more__(), or __len__() if random-access. */
   bool __more__ () const { return thiz()->__len__ (); }
@@ -129,6 +129,11 @@ struct hb_iter_mixin_t
 
   /* Random access: Return true if item_at(), len(), forward() are fast. */
   bool __random_access__ () const { return false; }
+
+  protected:
+  hb_iter_mixin_t () {}
+  hb_iter_mixin_t (const hb_iter_mixin_t &o HB_UNUSED) {}
+  void operator = (const hb_iter_mixin_t &o HB_UNUSED) {}
 };
 
 
diff --git a/src/hb-set.hh b/src/hb-set.hh
index 81b9064d5..640723e4f 100644
--- a/src/hb-set.hh
+++ b/src/hb-set.hh
@@ -671,20 +671,22 @@ struct hb_set_t
   /*
    * Iterator implementation.
    */
-  struct const_iter_t : hb_sorted_iter_t<const_iter_t, const hb_codepoint_t>
+  struct const_iter_t :
+    hb_sorted_iter_t<const_iter_t, const hb_codepoint_t>,
+    hb_iter_mixin_t<const_iter_t, const hb_codepoint_t>
   {
-    const_iter_t (const hb_set_t &s_) :
-      s (s_), v (INVALID), l (s.get_population () + 1) { __next__ (); }
+    const_iter_t (const hb_set_t &s_ = Null(hb_set_t)) :
+      s (&s_), v (INVALID), l (s->get_population () + 1) { __next__ (); }
 
     typedef hb_codepoint_t __item_type__;
-    hb_codepoint_t __item__ () const { return v; }
+    const hb_codepoint_t& __item__ () const { return v; }
     bool __more__ () const { return v != INVALID; }
-    void __next__ () { s.next (&v); if (l) l--; }
-    void __prev__ () { s.previous (&v); }
-    unsigned __len__ () { return l; }
+    void __next__ () { s->next (&v); if (l) l--; }
+    void __prev__ () { s->previous (&v); }
+    unsigned __len__ () const { return l; }
 
     protected:
-    const hb_set_t &s;
+    const hb_set_t *s;
     hb_codepoint_t v;
     unsigned l;
   };
diff --git a/src/test-iter.cc b/src/test-iter.cc
index 05430b009..5f69a928c 100644
--- a/src/test-iter.cc
+++ b/src/test-iter.cc
@@ -61,6 +61,27 @@ struct some_array_t
   hb_array_t<T> arr;
 };
 
+
+template <typename Iterator> static void
+test_iterator (Iterator it)
+{
+  /* Iterate over a copy of it. */
+  for (auto c = it.iter (); c; c++)
+    *c;
+
+  it += it.len () + 10;
+  it = it + 10;
+
+  assert (*it == it[0]);
+}
+
+template <typename Iterable> static void
+test_iterable (Iterable &lst)
+{
+  // Test that can take iterator from.
+  test_iterator (lst.iter ());
+}
+
 int
 main (int argc, char **argv)
 {
@@ -80,5 +101,9 @@ main (int argc, char **argv)
   hb_copy (t, s);
  // hb_copy (t, a.iter ());
 
+  test_iterable (v);
+  hb_set_t st;
+  test_iterable (st);
+
   return 0;
 }