Add hb_face_count, a new API (#1002)

Simply, it returns the number of faces on a font blob.

To be used on hb-sanitizer tool but other clients also
can benefit from it.

TODO

@@ -27,8 +27,6 @@ API additions
 
 - Add query / enumeration API for aalt-like features?
 
-- SFNT api? get_num_faces?
-
 - Add segmentation API
 
 - Add hb-fribidi glue?

docs/harfbuzz-sections.txt

@@ -169,6 +169,7 @@ hb_coretext_font_get_ct_font
 
 <SECTION>
 <FILE>hb-face</FILE>
+hb_face_count
 hb_face_create
 hb_face_create_for_tables
 hb_face_destroy

src/hb-face.cc

@@ -35,6 +35,29 @@
 #include "hb-ot-maxp-table.hh"
 
 
+
+/**
+ * hb_face_count: Get number of faces on the blob
+ * @blob:
+ *
+ *
+ *
+ * Return value: Number of faces on the blob
+ *
+ * Since: REPLACEME
+ **/
+unsigned int
+hb_face_count (hb_blob_t *blob)
+{
+  if (unlikely (!blob))
+    return 0;
+
+  hb_blob_t *sanitized = OT::Sanitizer<OT::OpenTypeFontFile> ().sanitize (blob);
+  const OT::OpenTypeFontFile& ot = *OT::Sanitizer<OT::OpenTypeFontFile>::lock_instance (sanitized);
+
+  return ot.get_face_count ();
+}
+
 /*
  * hb_face_t
  */

src/hb-face.h

@@ -37,6 +37,10 @@
 HB_BEGIN_DECLS
 
 
+HB_EXTERN unsigned int
+hb_face_count (hb_blob_t *blob);
+
+
 /*
  * hb_face_t
  */