[set] Add add_sorted_array()

Not optimized to use sortedness yet.  Also start putting in place infra
to faster reject bad data.

A version of Chandas.ttf found on some Chrome bots has 660kb of GPOS,
mostly junk.  That is causing 48 million of set->add() calls in
collect_glyphs(), which is insane.

In the upcoming commits, I'll be speeding that up by optimizing
add_sorted_array(), while also reducing work by rejecting out-of-sort
arrays quickly and propagate the rejection.

Part of https://bugs.chromium.org/p/chromium/issues/detail?id=794896

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

@@ -155,8 +155,9 @@ struct RangeRecord
   }
 
   template <typename set_t>
-  inline void add_coverage (set_t *glyphs) const {
+  inline bool add_coverage (set_t *glyphs) const {
     glyphs->add_range (start, end);
+    return likely (start <= end);
   }
 
   GlyphID	start;		/* First GlyphID in the range */
@@ -715,8 +716,8 @@ struct CoverageFormat1
   }
 
   template <typename set_t>
-  inline void add_coverage (set_t *glyphs) const {
-    glyphs->add_array (glyphArray.array, glyphArray.len);
+  inline bool add_coverage (set_t *glyphs) const {
+    return glyphs->add_sorted_array (glyphArray.array, glyphArray.len);
   }
 
   public:
@@ -815,10 +816,12 @@ struct CoverageFormat2
   }
 
   template <typename set_t>
-  inline void add_coverage (set_t *glyphs) const {
+  inline bool add_coverage (set_t *glyphs) const {
     unsigned int count = rangeRecord.len;
     for (unsigned int i = 0; i < count; i++)
-      rangeRecord[i].add_coverage (glyphs);
+      if (unlikely (!rangeRecord[i].add_coverage (glyphs)))
+        return false;
+    return true;
   }
 
   public:
@@ -925,12 +928,14 @@ struct Coverage
     }
   }
 
+  /* Might return false if array looks unsorted.
+   * Used for faster rejection of corrupt data. */
   template <typename set_t>
-  inline void add_coverage (set_t *glyphs) const {
+  inline bool add_coverage (set_t *glyphs) const {
     switch (u.format) {
-    case 1: u.format1.add_coverage (glyphs); break;
-    case 2: u.format2.add_coverage (glyphs); break;
-    default:                                 break;
+    case 1: return u.format1.add_coverage (glyphs);
+    case 2: return u.format2.add_coverage (glyphs);
+    default:return false;
     }
   }
 
@@ -1016,11 +1021,15 @@ struct ClassDefFormat1
   }
 
   template <typename set_t>
-  inline void add_class (set_t *glyphs, unsigned int klass) const {
+  inline bool add_class (set_t *glyphs, unsigned int min_klass, unsigned int max_klass) const {
     unsigned int count = classValue.len;
     for (unsigned int i = 0; i < count; i++)
-      if (classValue[i] == klass)
+    {
+      unsigned int klass = classValue[i];
+      if (min_klass <= klass && klass <= max_klass)
         glyphs->add (startGlyph + i);
+    }
+    return true;
   }
 
   inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
@@ -1073,11 +1082,16 @@ struct ClassDefFormat2
   }
 
   template <typename set_t>
-  inline void add_class (set_t *glyphs, unsigned int klass) const {
+  inline bool add_class (set_t *glyphs, unsigned int min_klass, unsigned int max_klass) const {
     unsigned int count = rangeRecord.len;
     for (unsigned int i = 0; i < count; i++)
-      if (rangeRecord[i].value == klass)
-        rangeRecord[i].add_coverage (glyphs);
+    {
+      unsigned int klass = rangeRecord[i].value;
+      if (min_klass <= klass && klass <= max_klass)
+        if (unlikely (!rangeRecord[i].add_coverage (glyphs)))
+	  return false;
+    }
+    return true;
   }
 
   inline bool intersects_class (const hb_set_t *glyphs, unsigned int klass) const {
@@ -1135,11 +1149,12 @@ struct ClassDef
     }
   }
 
-  inline void add_class (hb_set_t *glyphs, unsigned int klass) const {
+  template <typename set_t>
+  inline bool add_class (set_t *glyphs, unsigned int min_klass, unsigned int max_klass) const {
     switch (u.format) {
-    case 1: u.format1.add_class (glyphs, klass); return;
-    case 2: u.format2.add_class (glyphs, klass); return;
-    default:return;
+    case 1: return u.format1.add_class (glyphs, min_klass, max_klass);
+    case 2: return u.format2.add_class (glyphs, min_klass, max_klass);
+    default:return false;
     }
   }
 

src/hb-ot-layout-gdef-table.hh

@@ -352,7 +352,7 @@ struct GDEF
   inline unsigned int get_glyph_class (hb_codepoint_t glyph) const
   { return (this+glyphClassDef).get_class (glyph); }
   inline void get_glyphs_in_class (unsigned int klass, hb_set_t *glyphs) const
-  { (this+glyphClassDef).add_class (glyphs, klass); }
+  { (this+glyphClassDef).add_class (glyphs, klass, klass); }
 
   inline bool has_mark_attachment_types (void) const { return markAttachClassDef != 0; }
   inline unsigned int get_mark_attachment_type (hb_codepoint_t glyph) const

src/hb-ot-layout-gpos-table.hh

@@ -758,14 +758,12 @@ struct PairPosFormat2
     (this+coverage).add_coverage (c->input);
 
     unsigned int count1 = class1Count;
-    const ClassDef &klass1 = this+classDef1;
-    for (unsigned int i = 0; i < count1; i++)
-      klass1.add_class (c->input, i);
+    if (count1)
+      (this+classDef1).add_class (c->input, 0, count1 - 1);
 
     unsigned int count2 = class2Count;
-    const ClassDef &klass2 = this+classDef2;
-    for (unsigned int i = 0; i < count2; i++)
-      klass2.add_class (c->input, i);
+    if (count2)
+      (this+classDef2).add_class (c->input, 0, count2 - 1);
   }
 
   inline const Coverage &get_coverage (void) const

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

@@ -621,7 +621,7 @@ static inline void collect_glyph (hb_set_t *glyphs, const UINT16 &value, const v
 static inline void collect_class (hb_set_t *glyphs, const UINT16 &value, const void *data)
 {
   const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);
-  class_def.add_class (glyphs, value);
+  class_def.add_class (glyphs, value, value);
 }
 static inline void collect_coverage (hb_set_t *glyphs, const UINT16 &value, const void *data)
 {

src/hb-set-digest-private.hh

@@ -80,11 +80,25 @@ 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)
+  inline void add_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
   {
     for (unsigned int i = 0; i < count; i++)
-      add (array[i]);
+    {
+      add (*array);
+      array = (const T *) (stride + (const char *) array);
+    }
+  }
+  template <typename T>
+  inline bool add_sorted_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    for (unsigned int i = 0; i < count; i++)
+    {
+      add (*array);
+      array = (const T *) (stride + (const char *) array);
+    }
+    return true;
   }
 
   inline bool may_have (hb_codepoint_t g) const {
@@ -119,10 +133,17 @@ struct hb_set_digest_combiner_t
     tail.add_range (a, b);
   }
   template <typename T>
-  inline void add_array (const T *array, unsigned int count)
+  inline void add_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
   {
-    head.add_array (array, count);
-    tail.add_array (array, count);
+    head.add_array (array, count, stride);
+    tail.add_array (array, count, stride);
+  }
+  template <typename T>
+  inline bool add_sorted_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    head.add_sorted_array (array, count, stride);
+    tail.add_sorted_array (array, count, stride);
+    return true;
   }
 
   inline bool may_have (hb_codepoint_t g) const {

src/hb-set-private.hh

@@ -259,12 +259,29 @@ struct hb_set_t
       page->add_range (major_start (mb), b);
     }
   }
+
   template <typename T>
-  inline void add_array (const T *array, unsigned int count)
+  inline void add_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
   {
     for (unsigned int i = 0; i < count; i++)
-      add (array[i]);
+    {
+      add (*array);
+      array = (const T *) (stride + (const char *) array);
+    }
   }
+  /* Might return false if array looks unsorted.
+   * Used for faster rejection of corrupt data. */
+  template <typename T>
+  inline bool add_sorted_array (const T *array, unsigned int count, unsigned int stride=sizeof(T))
+  {
+    for (unsigned int i = 0; i < count; i++)
+    {
+      add (*array);
+      array = (const T *) (stride + (const char *) array);
+    }
+    return true;
+  }
+
   inline void del (hb_codepoint_t g)
   {
     if (unlikely (in_error)) return;