[subset] Add hb_subset_cff_get_charstrings_index and hb_subset_cff2_get_charstrings_index.

These methods allow retrieving the entire charstrings index structure from a CFF or CFF2 table.

docs/harfbuzz-sections.txt

@@ -956,7 +956,9 @@ hb_subset_serialize_or_fail
 <SUBSECTION Private>
 hb_subset_input_override_name_table
 hb_subset_cff_get_charstring_data
+hb_subset_cff_get_charstrings_index
 hb_subset_cff2_get_charstring_data
+hb_subset_cff2_get_charstrings_index
 </SECTION>
 
 <SECTION>

src/gen-def.py

@@ -22,7 +22,9 @@ if '--experimental-api' not in sys.argv:
 """hb_shape_justify
 hb_subset_input_override_name_table
 hb_subset_cff_get_charstring_data
+hb_subset_cff_get_charstrings_index
 hb_subset_cff2_get_charstring_data
+hb_subset_cff2_get_charstrings_index
 """.splitlines ()
 	symbols = [x for x in symbols if x not in experimental_symbols]
 symbols = "\n".join (symbols)

src/hb-subset.cc

@@ -737,6 +737,27 @@ static hb_blob_t* get_charstrings_data(accel_t& accel, hb_codepoint_t glyph_inde
   return hb_blob_create_sub_blob(cff_blob, (uint32_t) offset, bytes.length);
 }
 
+template<typename accel_t>
+static hb_blob_t* get_charstrings_index(accel_t& accel) {
+  if (!accel.is_valid()) {
+    return hb_blob_get_empty ();
+  }
+
+  const char* charstrings_start = (const char*) accel.charStrings;
+  unsigned charstrings_length = accel.charStrings->get_size();
+
+  hb_blob_t* cff_blob = accel.get_blob();
+  uint32_t length;
+  const char* cff_data = hb_blob_get_data(cff_blob, &length) ;
+
+  long int offset = charstrings_start - cff_data;
+  if (offset < 0 || offset > UINT32_MAX) {
+    return hb_blob_get_empty ();
+  }
+
+  return hb_blob_create_sub_blob(cff_blob, (uint32_t) offset, charstrings_length);
+}
+
 /**
  * hb_subset_cff_get_charstring_data:
  * @face: A face object
@@ -746,12 +767,25 @@ static hb_blob_t* get_charstrings_data(accel_t& accel, hb_codepoint_t glyph_inde
  *
  * XSince: EXPERIMENTAL
  **/
- HB_EXTERN hb_blob_t*
- hb_subset_cff_get_charstring_data(hb_face_t* face, hb_codepoint_t glyph_index) {
+HB_EXTERN hb_blob_t*
+hb_subset_cff_get_charstring_data(hb_face_t* face, hb_codepoint_t glyph_index) {
   return get_charstrings_data(*face->table.cff1, glyph_index);
- }
+}
 
- /**
+/**
+ * hb_subset_cff_get_charstrings_index:
+ * @face: A face object
+ *
+ * Returns the raw CFF CharStrings INDEX from the CFF table.
+ *
+ * XSince: EXPERIMENTAL
+ **/
+HB_EXTERN hb_blob_t*
+hb_subset_cff_get_charstrings_index (hb_face_t* face) {
+  return get_charstrings_index (*face->table.cff1);
+}
+ 
+/**
  * hb_subset_cff2_get_charstring_data:
  * @face: A face object
  * @glyph_index: Glyph index to get data for.
@@ -760,8 +794,21 @@ static hb_blob_t* get_charstrings_data(accel_t& accel, hb_codepoint_t glyph_inde
  *
  * XSince: EXPERIMENTAL
  **/
- HB_EXTERN hb_blob_t*
- hb_subset_cff2_get_charstring_data(hb_face_t* face, hb_codepoint_t glyph_index) {
+HB_EXTERN hb_blob_t*
+hb_subset_cff2_get_charstring_data(hb_face_t* face, hb_codepoint_t glyph_index) {
   return get_charstrings_data(*face->table.cff2, glyph_index);
- }
- #endif
+}
+
+/**
+ * hb_subset_cff2_get_charstrings_index:
+ * @face: A face object
+ *
+ * Returns the raw CFF2 CharStrings INDEX from the CFF2 table.
+ *
+ * XSince: EXPERIMENTAL
+ **/
+HB_EXTERN hb_blob_t*
+hb_subset_cff2_get_charstrings_index (hb_face_t* face) {
+  return get_charstrings_index (*face->table.cff2);
+}
+#endif

src/hb-subset.h

@@ -234,8 +234,14 @@ hb_subset_input_override_name_table (hb_subset_input_t  *input,
 HB_EXTERN hb_blob_t*
 hb_subset_cff_get_charstring_data (hb_face_t* face, hb_codepoint_t glyph_index);
 
+HB_EXTERN hb_blob_t*
+hb_subset_cff_get_charstrings_index (hb_face_t* face);
+
 HB_EXTERN hb_blob_t*
 hb_subset_cff2_get_charstring_data (hb_face_t* face, hb_codepoint_t glyph_index);
+
+HB_EXTERN hb_blob_t*
+hb_subset_cff2_get_charstrings_index (hb_face_t* face);
 #endif
 
 HB_EXTERN hb_face_t *

test/api/test-subset.c

@@ -248,6 +248,11 @@ const uint8_t CFF2[226] = {
   0x10, 0x06
 };
 
+const uint8_t CFF2_ONLY_CHARSTRINGS[12] = {
+  0x00, 0x00, 0x00, 0x02, 0x01, 0x01, 0x03, 0x05,
+  0x20, 0x0A, 0x20, 0x0A
+};
+
 static void
 test_subset_cff2_get_charstring_data (void)
 {
@@ -291,6 +296,39 @@ test_subset_cff2_get_charstring_data (void)
   hb_blob_destroy (cs2);
 }
 
+static void
+test_subset_cff2_get_all_charstrings_data (void)
+{
+  const uint8_t maxp_data[6] = {
+    0x00, 0x00, 0x50, 0x00,
+    0x00, 0x02 // numGlyphs
+  };
+
+  hb_blob_t* cff2 = hb_blob_create ((const char*) CFF2, 226, HB_MEMORY_MODE_READONLY, 0, 0);
+  hb_blob_t* maxp = hb_blob_create ((const char*) maxp_data, 6, HB_MEMORY_MODE_READONLY, 0, 0);
+  hb_face_t* builder = hb_face_builder_create ();
+  hb_face_builder_add_table (builder, HB_TAG('C', 'F', 'F', '2'), cff2);
+  hb_face_builder_add_table (builder, HB_TAG('m', 'a', 'x', 'p'), maxp);
+  hb_blob_t* face_blob = hb_face_reference_blob (builder);
+  hb_face_t* face = hb_face_create (face_blob, 0);
+
+  hb_blob_t* cs = hb_subset_cff2_get_charstrings_index (face);
+  hb_blob_destroy (cff2);
+  hb_blob_destroy (maxp);
+  hb_face_destroy (builder);
+  hb_blob_destroy (face_blob);
+  hb_face_destroy (face);
+
+  unsigned int length;
+  const uint8_t* data = (const uint8_t*) hb_blob_get_data (cs, &length);
+  g_assert_cmpint (length, ==, 12);
+  for (int i = 0; i < 12; i++) {
+    g_assert_cmpint(data[i], ==, CFF2_ONLY_CHARSTRINGS[i]);
+  }
+
+  hb_blob_destroy (cs);
+}
+
 static void
 test_subset_cff2_get_charstring_data_no_cff (void)
 {
@@ -304,8 +342,7 @@ test_subset_cff2_get_charstring_data_no_cff (void)
   hb_face_destroy (builder);
   hb_blob_destroy (face_blob);
   hb_face_destroy (face);
-  hb_blob_destroy
-   (cs0);
+  hb_blob_destroy (cs0);
 }
 
 static void
@@ -381,6 +418,7 @@ main (int argc, char **argv)
 
   #ifdef HB_EXPERIMENTAL_API
   hb_test_add (test_subset_cff2_get_charstring_data);
+  hb_test_add (test_subset_cff2_get_all_charstrings_data);
   hb_test_add (test_subset_cff2_get_charstring_data_no_cff);
   hb_test_add (test_subset_cff2_get_charstring_data_invalid_cff2);
   hb_test_add (test_subset_cff2_get_charstring_data_lifetime);