diff --git a/src/Makefile.sources b/src/Makefile.sources
index fb4e4a2c4..80b8e261c 100644
--- a/src/Makefile.sources
+++ b/src/Makefile.sources
@@ -14,6 +14,7 @@ HB_BASE_sources = \
 	hb-face.cc \
 	hb-font-private.hh \
 	hb-font.cc \
+	hb-iter-private.hh \
 	hb-map-private.hh \
 	hb-map.cc \
 	hb-machinery-private.hh \
diff --git a/src/hb-iter-private.hh b/src/hb-iter-private.hh
new file mode 100644
index 000000000..a22675cd7
--- /dev/null
+++ b/src/hb-iter-private.hh
@@ -0,0 +1,147 @@
+/*
+ * Copyright © 2018  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_ITER_PRIVATE_HH
+#define HB_ITER_PRIVATE_HH
+
+#include "hb-private.hh"
+
+
+/* Unified iterator object.
+ *
+ * The goal of this template is to make the same iterator interface
+ * available to all types, and make it very easy and compact to use.
+ * Iterator objects are small, light-weight, objects that can be
+ * copied by value.  If the collection / object being iterated on
+ * is writable, then the iterator points to lvalues, otherwise it
+ * returns rvalues.
+ *
+ * The way to declare, initialize, and use iterators, eg.:
+ *
+ *   Iter<const int *> s (src);
+ *   Iter<int *> t (dst);
+ *   for (; s && t; s++, t++)
+ *     *s = *t;
+ */
+
+template <typename T>
+struct Iter;
+
+template <typename T>
+struct Iter
+{
+  inline Iter (const T &c);
+};
+
+template <typename T>
+struct Iter<T *>
+{
+  /* Type of items. */
+  typedef T Value;
+
+  /* Constructors. */
+  inline Iter (T *array_, int length_) :
+    array (array_), length (MAX (length_, 0)) {}
+  template <unsigned int length_>
+  inline Iter (T (&array_)[length_]) :
+    array (array_), length (length_) {}
+
+  /* Emptiness. */
+  inline operator bool (void) const { return bool (length); }
+
+  /* Current item. */
+  inline T &operator * (void)
+  {
+    if (unlikely (!length)) return CrapOrNull(T);
+    return *array;
+  }
+  inline T &operator -> (void)
+  {
+    return (operator *);
+  }
+
+  /* Next. */
+  inline Iter<T *> & operator ++ (void)
+  {
+    if (unlikely (!length)) return *this;
+    array++;
+    length--;
+    return *this;
+  }
+  /* Might return void, or a copy of pre-increment iterator. */
+  inline void operator ++ (int)
+  {
+    if (unlikely (!length)) return;
+    array++;
+    length--;
+  }
+
+  /* Some iterators might implement len(). */
+  inline unsigned int len (void) const { return length; }
+
+  /* Some iterators might implement fast-forward.
+   * Only implement it if it's constant-time. */
+  inline void operator += (unsigned int n)
+  {
+    n = MIN (n, length);
+    array += n;
+    length -= n;
+  }
+
+  /* Some iterators might implement random-access.
+   * Only implement it if it's constant-time. */
+  inline Iter<T *> & operator [] (unsigned int i)
+  {
+    if (unlikely (i >= length)) return CrapOrNull(T);
+    return array[i];
+  }
+
+  private:
+  T *array;
+  unsigned int length;
+};
+
+/* XXX Remove
+ * Just to test these compile. */
+static inline void
+m (void)
+{
+  const int src[10] = {};
+  int dst[20];
+
+  Iter<const int *> s (src);
+  Iter<const int *> s2 (src, 5);
+  Iter<int *> t (dst);
+
+  s2 = s;
+
+  for (; s && t; s++, t++)
+   {
+    *t = *s;
+   }
+}
+
+#endif /* HB_ITER_PRIVATE_HH */
diff --git a/src/hb-machinery-private.hh b/src/hb-machinery-private.hh
index 5fafadbec..649788c16 100644
--- a/src/hb-machinery-private.hh
+++ b/src/hb-machinery-private.hh
@@ -30,6 +30,7 @@
 #define HB_MACHINERY_PRIVATE_HH
 
 #include "hb-private.hh"
+#include "hb-iter-private.hh"
 
 
 namespace OT {