From fa35d3fd81c1ddb847cdd83556f817db9ef7f35b Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@fb.com>
Date: Thu, 14 Feb 2019 14:04:05 -0800
Subject: [PATCH] [iter] Add hb_drain

---
 src/hb-iter.hh   | 11 +++++++++++
 src/test-iter.cc |  7 ++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/hb-iter.hh b/src/hb-iter.hh
index 2c885d676..730f6824c 100644
--- a/src/hb-iter.hh
+++ b/src/hb-iter.hh
@@ -430,6 +430,17 @@ static const struct
   { return hb_sink_t<Sink&> (*s); }
 } hb_sink HB_UNUSED;
 
+static const struct
+{
+  template <typename Iter,
+	    hb_enable_if (hb_is_iterator (Iter))>
+  void
+  operator () (Iter it) const
+  {
+    for (; it; ++it)
+      (void) *it;
+  }
+} hb_drain HB_UNUSED;
 
 /*
  * Algorithms operating on iterators.
diff --git a/src/test-iter.cc b/src/test-iter.cc
index a96616369..d7e9a00ea 100644
--- a/src/test-iter.cc
+++ b/src/test-iter.cc
@@ -149,7 +149,12 @@ main (int argc, char **argv)
   ;
 
   + hb_iter (src)
-  | hb_apply (&st);
+  | hb_apply (&st)
+  ;
+
+  + hb_iter (src)
+  | hb_drain
+  ;
 
   t << 1;
   long vl;