[set] Add add_array()

To be used to optimize adding a whole bunch of (sorted) items at the same time,
as in CoverageFormat1.

src/hb-ot-layout-common-private.hh

@@ -716,9 +716,7 @@ struct CoverageFormat1
 
   template <typename set_t>
   inline void add_coverage (set_t *glyphs) const {
-    unsigned int count = glyphArray.len;
+    glyphs->add_array (glyphArray.array, glyphArray.len);
-    for (unsigned int i = 0; i < count; i++)
-      glyphs->add (glyphArray[i]);
   }
 
   public:

src/hb-set-digest-private.hh

@@ -80,6 +80,12 @@ struct hb_set_digest_lowest_bits_t
       mask |= mb + (mb - ma) - (mb < ma);
     }
   }
+  template <typename T>
+  inline void add_array (const T *array, unsigned int count)
+  {
+    for (unsigned int i = 0; i < count; i++)
+      add (array[i]);
+  }
 
   inline bool may_have (hb_codepoint_t g) const {
     return !!(mask & mask_for (g));
@@ -112,6 +118,12 @@ struct hb_set_digest_combiner_t
     head.add_range (a, b);
     tail.add_range (a, b);
   }
+  template <typename T>
+  inline void add_array (const T *array, unsigned int count)
+  {
+    head.add_array (array, count);
+    tail.add_array (array, count);
+  }
 
   inline bool may_have (hb_codepoint_t g) const {
     return head.may_have (g) && tail.may_have (g);

src/hb-set-private.hh

@@ -248,6 +248,12 @@ struct hb_set_t
       page->add_range (major_start (mb), b);
     }
   }
+  template <typename T>
+  inline void add_array (const T *array, unsigned int count)
+  {
+    for (unsigned int i = 0; i < count; i++)
+      add (array[i]);
+  }
   inline void del (hb_codepoint_t g)
   {
     if (unlikely (in_error)) return;