Set hb_buffer_t to use array_t.reverse().

src/Makefile.am

@@ -352,6 +352,10 @@ test_buffer_serialize_SOURCES = test-buffer-serialize.cc
 test_buffer_serialize_CPPFLAGS = $(HBCFLAGS)
 test_buffer_serialize_LDADD = libharfbuzz.la $(HBLIBS)
 
+test_array_SOURCES = test-array.cc
+test_array_CPPFLAGS = $(HBCFLAGS)
+test_array_LDADD = libharfbuzz.la $(HBLIBS)
+
 test_ot_meta_SOURCES = test-ot-meta.cc
 test_ot_meta_CPPFLAGS = $(HBCFLAGS)
 test_ot_meta_LDADD = libharfbuzz.la $(HBLIBS)
@@ -407,7 +411,7 @@ dump_use_data_SOURCES = dump-use-data.cc hb-ot-shape-complex-use-table.cc
 dump_use_data_CPPFLAGS = $(HBCFLAGS)
 dump_use_data_LDADD = libharfbuzz.la $(HBLIBS)
 
-COMPILED_TESTS = test-algs test-iter test-meta test-number test-ot-tag test-unicode-ranges test-bimap
+COMPILED_TESTS = test-algs test-array test-iter test-meta test-number test-ot-tag test-unicode-ranges test-bimap
 COMPILED_TESTS_CPPFLAGS = $(HBCFLAGS) -DMAIN -UNDEBUG
 COMPILED_TESTS_LDADD = libharfbuzz.la $(HBLIBS)
 check_PROGRAMS += $(COMPILED_TESTS)

src/hb-array.hh

@@ -171,18 +171,21 @@ struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
 
   unsigned int get_size () const { return length * this->get_item_size (); }
 
-  void reverse ()
+  /*
+   * Reverse the order of items in this array in the range [start, end).
+   */
+  void reverse (unsigned start = 0, unsigned end = -1)
   {
-    int rhs = length - 1;
-    int lhs = 0;
-    while (rhs > lhs)
-    {
-      Type value_rhs = arrayZ[rhs];
-      Type value_lhs = arrayZ[lhs];
-      arrayZ[rhs] = value_lhs;
-      arrayZ[lhs] = value_rhs;
-      rhs--;
-      lhs++;
+    start = hb_min (start, length);
+    end = hb_min (end, length);
+
+    if (end < start + 2)
+      return;
+
+    for (unsigned lhs = start, rhs = end - 1; lhs < rhs; lhs++, rhs--) {
+      Type temp = arrayZ[rhs];
+      arrayZ[rhs] = arrayZ[lhs];
+      arrayZ[lhs] = temp;
     }
   }
 

src/hb-buffer.cc

@@ -448,27 +448,13 @@ void
 hb_buffer_t::reverse_range (unsigned int start,
 			    unsigned int end)
 {
-  unsigned int i, j;
-
   if (end - start < 2)
     return;
 
-  for (i = start, j = end - 1; i < j; i++, j--) {
-    hb_glyph_info_t t;
-
-    t = info[i];
-    info[i] = info[j];
-    info[j] = t;
-  }
+  hb_array_t<hb_glyph_info_t> (info, len).reverse (start, end);
 
   if (have_positions) {
-    for (i = start, j = end - 1; i < j; i++, j--) {
-      hb_glyph_position_t t;
-
-      t = pos[i];
-      pos[i] = pos[j];
-      pos[j] = t;
-    }
+    hb_array_t<hb_glyph_position_t> (pos, len).reverse (start, end);
   }
 }
 

src/test-array.cc

@@ -0,0 +1,76 @@
+/*
+ * Copyright © 2020  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): Garret Rieger
+ */
+
+#include "hb.hh"
+#include "hb-array.hh"
+
+static void
+test_reverse ()
+{
+  int values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+  hb_array_t<int> a (values, 9);
+  a.reverse();
+
+  int expected_values[] = {9, 8, 7, 6, 5, 4, 3, 2, 1};
+  hb_array_t<int> expected (expected_values, 9);
+  assert (a == expected);
+}
+
+static void
+test_reverse_range ()
+{
+  int values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+  hb_array_t<int> a (values, 9);
+  a.reverse(2, 6);
+
+  int expected_values[] = {1, 2, 6, 5, 4, 3, 7, 8, 9};
+  hb_array_t<int> expected (expected_values, 9);
+  assert (a == expected);
+}
+
+static void
+test_reverse_invalid ()
+{
+  int values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+  hb_array_t<int> a (values, 9);
+
+  a.reverse(4, 3);
+  a.reverse(2, 3);
+  a.reverse(5, 5);
+  a.reverse(12, 15);
+
+  int expected_values[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+  hb_array_t<int> expected (expected_values, 9);
+  assert (a == expected);
+}
+
+int
+main (int argc, char **argv)
+{
+  test_reverse ();
+  test_reverse_range ();
+  test_reverse_invalid ();
+}