Use insertion-sort instead of bubble-sort

Needed for upcoming merge-clusters fix.

src/hb-buffer.cc

@@ -1636,7 +1636,7 @@ normalize_glyphs_cluster (hb_buffer_t *buffer,
     pos[end - 1].x_advance = total_x_advance;
     pos[end - 1].y_advance = total_y_advance;
 
-    hb_bubble_sort (buffer->info + start, end - start - 1, compare_info_codepoint, buffer->pos + start);
+    hb_stable_sort (buffer->info + start, end - start - 1, compare_info_codepoint, buffer->pos + start);
   } else {
     /* Transfer all cluster advance to the first glyph. */
     pos[start].x_advance += total_x_advance;
@@ -1645,7 +1645,7 @@ normalize_glyphs_cluster (hb_buffer_t *buffer,
       pos[i].x_offset -= total_x_advance;
       pos[i].y_offset -= total_y_advance;
     }
-    hb_bubble_sort (buffer->info + start + 1, end - start - 1, compare_info_codepoint, buffer->pos + start + 1);
+    hb_stable_sort (buffer->info + start + 1, end - start - 1, compare_info_codepoint, buffer->pos + start + 1);
   }
 }
 

src/hb-ot-shape-complex-arabic-fallback.hh

@@ -75,9 +75,9 @@ arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan HB_UNUS
   if (!num_glyphs)
     return NULL;
 
-  /* Bubble-sort!
+  /* Bubble-sort or something equally good!
    * May not be good-enough for presidential candidate interviews, but good-enough for us... */
-  hb_bubble_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
+  hb_stable_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
 
   OT::Supplier<OT::GlyphID> glyphs_supplier      (glyphs, num_glyphs);
   OT::Supplier<OT::GlyphID> substitutes_supplier (substitutes, num_glyphs);
@@ -126,7 +126,7 @@ arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UN
     first_glyphs_indirection[num_first_glyphs] = first_glyph_idx;
     num_first_glyphs++;
   }
-  hb_bubble_sort (&first_glyphs[0], num_first_glyphs, OT::GlyphID::cmp, &first_glyphs_indirection[0]);
+  hb_stable_sort (&first_glyphs[0], num_first_glyphs, OT::GlyphID::cmp, &first_glyphs_indirection[0]);
 
   /* Now that the first-glyphs are sorted, walk again, populate ligatures. */
   for (unsigned int i = 0; i < num_first_glyphs; i++)

src/hb-ot-shape-complex-indic.cc

@@ -1012,7 +1012,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
       info[i].syllable() = i - start;
 
     /* Sit tight, rock 'n roll! */
-    hb_bubble_sort (info + start, end - start, compare_indic_order);
+    hb_stable_sort (info + start, end - start, compare_indic_order);
     /* Find base again */
     base = end;
     for (unsigned int i = start; i < end; i++)

src/hb-ot-shape-complex-myanmar.cc

@@ -393,7 +393,7 @@ initial_reordering_consonant_syllable (hb_buffer_t *buffer,
 
   buffer->merge_clusters (start, end);
   /* Sit tight, rock 'n roll! */
-  hb_bubble_sort (info + start, end - start, compare_myanmar_order);
+  hb_stable_sort (info + start, end - start, compare_myanmar_order);
 }
 
 static void

src/hb-ot-shape-normalize.cc

@@ -344,15 +344,13 @@ _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
       if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
         break;
 
-    /* We are going to do a bubble-sort.  Only do this if the
+    /* We are going to do a O(n^2).  Only do this if the sequence is short. */
-     * sequence is short.  Doing it on long sequences can result
-     * in an O(n^2) DoS. */
     if (end - i > 10) {
       i = end;
       continue;
     }
 
-    hb_bubble_sort (buffer->info + i, end - i, compare_combining_class);
+    hb_stable_sort (buffer->info + i, end - i, compare_combining_class);
 
     i = end;
   }

src/hb-private.hh

@@ -855,42 +855,36 @@ hb_in_ranges (T u, T lo1, T hi1, T lo2, T hi2, T lo3, T hi3)
 
 
 template <typename T, typename T2> static inline void
-hb_bubble_sort (T *array, unsigned int len, int(*compar)(const T *, const T *), T2 *array2)
+hb_stable_sort (T *array, unsigned int len, int(*compar)(const T *, const T *), T2 *array2)
 {
-  if (unlikely (!len))
+  for (unsigned int i = 1; i < len; i++)
-    return;
-
-  unsigned int k = len - 1;
-  do {
-    unsigned int new_k = 0;
-
-    for (unsigned int j = 0; j < k; j++)
-      if (compar (&array[j], &array[j+1]) > 0)
   {
+    unsigned int j = i;
+    while (j && compar (&array[j - 1], &array[i]) > 0)
+      j--;
+    if (i == j)
+      continue;
+    /* Move item i to occupy place for item j, shift what's in between. */
     {
       T t;
-	  t = array[j];
+      t = array[i];
-	  array[j] = array[j + 1];
+      memmove (&array[j + 1], &array[j], (i - j) * sizeof (T));
-	  array[j + 1] = t;
+      array[j] = t;
     }
     if (array2)
     {
       T2 t;
-	  t = array2[j];
+      t = array2[i];
-	  array2[j] = array2[j + 1];
+      memmove (&array2[j + 1], &array2[j], (i - j) * sizeof (T2));
-	  array2[j + 1] = t;
+      array2[j] = t;
     }
-
-	new_k = j;
   }
-    k = new_k;
-  } while (k);
 }
 
 template <typename T> static inline void
-hb_bubble_sort (T *array, unsigned int len, int(*compar)(const T *, const T *))
+hb_stable_sort (T *array, unsigned int len, int(*compar)(const T *, const T *))
 {
-  hb_bubble_sort (array, len, compar, (int *) NULL);
+  hb_stable_sort (array, len, compar, (int *) NULL);
 }
 
 static inline hb_bool_t