[HB] Add OffsetTo template.

src/hb-ot-layout-gdef-private.h

@@ -228,34 +228,36 @@ struct GDEF {
   STATIC_DEFINE_GET_FOR_DATA (GDEF);
   /* XXX check version here? */
 
-  DEFINE_GET_HAS_ACCESSOR (ClassDef, glyph_classes, glyphClassDef);
-  DEFINE_GET_HAS_ACCESSOR (AttachList, attach_list, attachList);
-  DEFINE_GET_HAS_ACCESSOR (LigCaretList, lig_caret_list, ligCaretList);
-  DEFINE_GET_HAS_ACCESSOR (ClassDef, mark_attachment_types, markAttachClassDef);
-
+  inline bool has_glyph_classes () const { return glyphClassDef != 0; }
   inline hb_ot_layout_class_t get_glyph_class (hb_codepoint_t glyph) const {
-    return get_glyph_classes ().get_class (glyph);
+    return glyphClassDef(this).get_class (glyph);
   }
 
+  inline bool has_mark_attachment_types () const { return markAttachClassDef != 0; }
   inline hb_ot_layout_class_t get_mark_attachment_type (hb_codepoint_t glyph) const {
-    return get_mark_attachment_types ().get_class (glyph);
+    return markAttachClassDef(this).get_class (glyph);
   }
 
   /* TODO get_attach and get_lig_caret */
+  inline bool has_attach_list () const { return attachList != 0; }
+  inline bool has_lig_caret_list () const { return ligCaretList != 0; }
 
-  private:
   Fixed		version;		/* Version of the GDEF table--initially
 					 * 0x00010000 */
-  Offset	glyphClassDef;		/* Offset to class definition table
+  OffsetTo<ClassDef>
+		glyphClassDef;		/* Offset to class definition table
 					 * for glyph type--from beginning of
 					 * GDEF header (may be Null) */
-  Offset	attachList;		/* Offset to list of glyphs with
+  OffsetTo<AttachList>
+		attachList;		/* Offset to list of glyphs with
 					 * attachment points--from beginning
 					 * of GDEF header (may be Null) */
-  Offset	ligCaretList;		/* Offset to list of positioning points
+  OffsetTo<LigCaretList>
+		ligCaretList;		/* Offset to list of positioning points
 					 * for ligature carets--from beginning
 					 * of GDEF header (may be Null) */
-  Offset	markAttachClassDef;	/* Offset to class definition table for
+  OffsetTo<ClassDef>
+		markAttachClassDef;	/* Offset to class definition table for
 					 * mark attachment type--from beginning
 					 * of GDEF header (may be Null) */
 };

src/hb-ot-layout-gsub-private.h

@@ -793,7 +793,6 @@ struct ContextSubstFormat2 {
   /* SubClassSet tables, in Coverage Index order */
   DEFINE_OFFSET_ARRAY_TYPE (SubClassSet, subClassSet, subClassSetCnt);
   DEFINE_GET_ACCESSOR (Coverage, coverage, coverage);
-  DEFINE_GET_ACCESSOR (ClassDef, class_def, classDef);
   DEFINE_GET_GLYPH_COVERAGE (glyph_coverage);
 
   inline bool substitute (SUBTABLE_SUBSTITUTE_ARGS_DEF) const {
@@ -807,14 +806,15 @@ struct ContextSubstFormat2 {
     unsigned int index = get_glyph_coverage (glyph_id);
 
     const SubClassSet &class_set = (*this)[index];
-    return class_set.substitute_class (SUBTABLE_SUBSTITUTE_ARGS, get_class_def ());
+    return class_set.substitute_class (SUBTABLE_SUBSTITUTE_ARGS, this+classDef);
   }
 
   private:
   USHORT	substFormat;		/* Format identifier--format = 2 */
   Offset	coverage;		/* Offset to Coverage table--from
 					 * beginning of Substitution table */
-  Offset	classDef;		/* Offset to glyph ClassDef table--from
+  OffsetTo<ClassDef>
+		classDef;		/* Offset to glyph ClassDef table--from
 					 * beginning of Substitution  table */
   USHORT	subClassSetCnt;		/* Number of SubClassSet tables */
   Offset	subClassSet[];		/* Array of offsets to SubClassSet

src/hb-ot-layout-open-private.h

@@ -242,11 +242,6 @@ struct Null <Type> { \
     if (HB_UNLIKELY (!Name)) return Null(Type); \
     return *(const Type*)((const char*)this + Name); \
   }
-#define DEFINE_GET_HAS_ACCESSOR(Type, name, Name) \
-  DEFINE_GET_ACCESSOR (Type, name, Name); \
-  inline bool has_##name (void) const { \
-    return Name != 0; \
-  }
 
 
 
@@ -340,6 +335,21 @@ DEFINE_INT_TYPE_STRUCT (GlyphID, u, 16);
 /* Offset to a table, same as uint16 (length = 16 bits), Null offset = 0x0000 */
 DEFINE_INT_TYPE_STRUCT (Offset, u, 16);
 
+/* Template subclass of Offset that does the dereferencing.  Use: (this+memberName) */
+template <typename Type>
+struct OffsetTo : Offset {
+  inline const Type& operator() (const void *base) const {
+    unsigned int offset = *this;
+    if (HB_UNLIKELY (!offset)) return Null(Type);
+    return * (const Type *) ((const char *) base + offset);
+  }
+};
+
+template <typename Base, typename Type>
+inline const Type& operator + (const Base &base, OffsetTo<Type> offset) {
+  return offset(base);
+}
+
 
 /* CheckSum */
 struct CheckSum : ULONG {
@@ -572,9 +582,7 @@ struct Script {
     return defaultLangSys != 0;
   }
   inline const LangSys& get_default_lang_sys (void) const {
-    if (HB_UNLIKELY (!defaultLangSys))
-      return Null(LangSys);
-    return *(LangSys*)((const char*)this + defaultLangSys);
+    return this+defaultLangSys;
   }
 
   private:
@@ -582,7 +590,8 @@ struct Script {
   DEFINE_RECORD_ARRAY_TYPE (LangSys, langSysRecord, langSysCount);
 
   private:
-  Offset	defaultLangSys;	/* Offset to DefaultLangSys table--from
+  OffsetTo<LangSys>
+		defaultLangSys;	/* Offset to DefaultLangSys table--from
 				 * beginning of Script table--may be Null */
   USHORT	langSysCount;	/* Number of LangSysRecords for this script--
 				 * excluding the DefaultLangSys */