diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index 06b923f22..d7d15f92a 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -217,10 +217,9 @@ struct hb_buffer_t
 
     reverse ();
 
-    unsigned count = len;
     unsigned start = 0;
     unsigned i;
-    for (i = 1; i < count; i++)
+    for (i = 1; i < len; i++)
     {
       if (!group (info[i - 1], info[i]))
       {
@@ -231,8 +230,20 @@ struct hb_buffer_t
     reverse_range (start, i);
   }
 
-  void reverse_clusters ()
-  { reverse_groups ([] (const hb_glyph_info_t& a, const hb_glyph_info_t& b) -> bool { return a.cluster == b.cluster; }); }
+  template <typename FuncType>
+  unsigned group_end (unsigned start, const FuncType& group) const
+  {
+    while (++start < len && group (info[start - 1], info[start]))
+      ;
+
+    return start;
+  }
+
+  static bool _cluster_group_func (const hb_glyph_info_t& a,
+				   const hb_glyph_info_t& b)
+  { return a.cluster == b.cluster; }
+
+  void reverse_clusters () { reverse_groups (_cluster_group_func); }
 
   HB_INTERNAL void guess_segment_properties ();
 
@@ -489,26 +500,15 @@ struct hb_buffer_t
 DECLARE_NULL_INSTANCE (hb_buffer_t);
 
 
-/* Loop over clusters. Duplicated in foreach_syllable(). */
-#define foreach_cluster(buffer, start, end) \
+#define foreach_group(buffer, start, end, group_func) \
   for (unsigned int \
        _count = buffer->len, \
-       start = 0, end = _count ? _next_cluster (buffer, 0) : 0; \
+       start = 0, end = _count ? buffer->group_end (0, group_func) : 0; \
        start < _count; \
-       start = end, end = _next_cluster (buffer, start))
+       start = end, end = buffer->group_end (start, group_func))
 
-static inline unsigned int
-_next_cluster (hb_buffer_t *buffer, unsigned int start)
-{
-  hb_glyph_info_t *info = buffer->info;
-  unsigned int count = buffer->len;
-
-  unsigned int cluster = info[start].cluster;
-  while (++start < count && cluster == info[start].cluster)
-    ;
-
-  return start;
-}
+#define foreach_cluster(buffer, start, end) \
+	foreach_group (buffer, start, end, hb_buffer_t::_cluster_group_func)
 
 
 #define HB_BUFFER_XALLOCATE_VAR(b, func, var) \