[set] Add is_subset

New API:
+hb_set_is_subset()

src/hb-set-private.hh

@@ -400,6 +400,19 @@ struct hb_set_t
     return true;
   }
 
+  inline bool is_subset (const hb_set_t *larger_set) const
+  {
+    if (get_population () > larger_set->get_population ())
+      return false;
+
+    hb_codepoint_t c = INVALID;
+    while (next (&c))
+      if (!larger_set->has (c))
+        return false;
+
+    return true;
+  }
+
   template <class Op>
   inline void process (const hb_set_t *other)
   {

src/hb-set.cc

@@ -267,11 +267,11 @@ hb_set_del_range (hb_set_t       *set,
 /**
  * hb_set_is_equal:
  * @set: a set.
- * @other: 
+ * @other: other set.
  *
  * 
  *
- * Return value: 
+ * Return value: %TRUE if the two sets are equal, %FALSE otherwise.
  *
  * Since: 0.9.7
  **/
@@ -282,6 +282,24 @@ hb_set_is_equal (const hb_set_t *set,
   return set->is_equal (other);
 }
 
+/**
+ * hb_set_is_subset:
+ * @set: a set.
+ * @larger_set: other set.
+ *
+ *
+ *
+ * Return value: %TRUE if the @set is a subset of (or equal to) @larger_set, %FALSE otherwise.
+ *
+ * Since: 1.8.1
+ **/
+hb_bool_t
+hb_set_is_subset (const hb_set_t *set,
+		  const hb_set_t *larger_set)
+{
+  return set->is_subset (larger_set);
+}
+
 /**
  * hb_set_set:
  * @set: a set.

src/hb-set.h

@@ -104,6 +104,10 @@ HB_EXTERN hb_bool_t
 hb_set_is_equal (const hb_set_t *set,
 		 const hb_set_t *other);
 
+HB_EXTERN hb_bool_t
+hb_set_is_subset (const hb_set_t *set,
+		  const hb_set_t *larger_set);
+
 HB_EXTERN void
 hb_set_set (hb_set_t       *set,
 	    const hb_set_t *other);

test/api/test-set.c

@@ -146,8 +146,12 @@ test_set_algebra (void)
 
   test_empty (s);
   g_assert (!hb_set_is_equal (s, o));
+  g_assert (hb_set_is_subset (s, o));
+  g_assert (!hb_set_is_subset (o, s));
   hb_set_set (s, o);
   g_assert (hb_set_is_equal (s, o));
+  g_assert (hb_set_is_subset (s, o));
+  g_assert (hb_set_is_subset (o, s));
   test_not_empty (s);
   g_assert_cmpint (hb_set_get_population (s), ==, 2);
 

test/api/test-subset-glyf.c

@@ -178,12 +178,11 @@ test_subset_glyf_strip_hints_invalid (void)
 
   hb_set_t *codepoints = hb_set_create();
   const hb_codepoint_t text[] =
-      {
-        'A', 'B', 'C', 'D', 'E', 'X', 'Y', 'Z', '1', '2',
-        '3', '@', '_', '%', '&', ')', '*', '$', '!'
-      };
-  int i;
-  for (i = 0; i < sizeof (text) / sizeof (hb_codepoint_t); i++)
+  {
+    'A', 'B', 'C', 'D', 'E', 'X', 'Y', 'Z', '1', '2',
+    '3', '@', '_', '%', '&', ')', '*', '$', '!'
+  };
+  for (unsigned int i = 0; i < sizeof (text) / sizeof (hb_codepoint_t); i++)
   {
     hb_set_add (codepoints, text[i]);
     // hb_set_add (codepoints_drop_hints, text[i]);