[subset/cff] Speed up subset_cff_fdselect

src/hb-ot-cff-common.hh

@@ -368,8 +368,11 @@ struct FDSelect0 {
     return_trace (true);
   }
 
-  hb_codepoint_t get_fd (hb_codepoint_t glyph) const
-  { return (hb_codepoint_t) fds[glyph]; }
+  unsigned get_fd (hb_codepoint_t glyph) const
+  { return fds[glyph]; }
+
+  hb_pair_t<unsigned, hb_codepoint_t> get_fd_range (hb_codepoint_t glyph) const
+  { return {fds[glyph], glyph + 1}; }
 
   unsigned int get_size (unsigned int num_glyphs) const
   { return HBUINT8::static_size * num_glyphs; }
@@ -427,12 +430,20 @@ struct FDSelect3_4
     return +1;
   }
 
-  hb_codepoint_t get_fd (hb_codepoint_t glyph) const
+  unsigned get_fd (hb_codepoint_t glyph) const
   {
     auto *range = hb_bsearch (glyph, &ranges[0], nRanges () - 1, sizeof (ranges[0]), _cmp_range);
     return range ? range->fd : ranges[nRanges () - 1].fd;
   }
 
+  hb_pair_t<unsigned, hb_codepoint_t> get_fd_range (hb_codepoint_t glyph) const
+  {
+    auto *range = hb_bsearch (glyph, &ranges[0], nRanges () - 1, sizeof (ranges[0]), _cmp_range);
+    unsigned fd = range ? range->fd : ranges[nRanges () - 1].fd;
+    hb_codepoint_t end = range ? range[1].first : 0;
+    return {fd, end};
+  }
+
   GID_TYPE        &nRanges ()       { return ranges.len; }
   GID_TYPE         nRanges () const { return ranges.len; }
   GID_TYPE       &sentinel ()       { return StructAfter<GID_TYPE> (ranges[nRanges () - 1]); }
@@ -469,7 +480,7 @@ struct FDSelect
     }
   }
 
-  hb_codepoint_t get_fd (hb_codepoint_t glyph) const
+  unsigned get_fd (hb_codepoint_t glyph) const
   {
     if (this == &Null (FDSelect)) return 0;
 
@@ -480,6 +491,18 @@ struct FDSelect
     default:return 0;
     }
   }
+  /* Returns pair of fd and one after last glyph in range. */
+  hb_pair_t<unsigned, hb_codepoint_t> get_fd_range (hb_codepoint_t glyph) const
+  {
+    if (this == &Null (FDSelect)) return {0, 0};
+
+    switch (format)
+    {
+    case 0: return u.format0.get_fd_range (glyph);
+    case 3: return u.format3.get_fd_range (glyph);
+    default:return {0, 0};
+    }
+  }
 
   bool sanitize (hb_sanitize_context_t *c, unsigned int fdcount) const
   {

src/hb-subset-cff-common.cc

@@ -68,6 +68,7 @@ hb_plan_subset_cff_fdselect (const hb_subset_plan_t *plan,
     /* use hb_set to determine the subset of font dicts */
     hb_set_t set;
     hb_codepoint_t prev_fd = CFF_UNDEF_CODE;
+    hb_pair_t<unsigned, hb_codepoint_t> last_range {0, 0};
     auto it = hb_iter (plan->new_to_old_gid_list);
     for (hb_codepoint_t gid = 0; gid < subset_num_glyphs; gid++)
     {
@@ -82,7 +83,9 @@ hb_plan_subset_cff_fdselect (const hb_subset_plan_t *plan,
 	/* fonttools retains FDSelect & font dicts for missing glyphs. do the same */
 	old_glyph = gid;
       }
-      unsigned fd = src.get_fd (old_glyph);
+      if (old_glyph >= last_range.second)
+	last_range = src.get_fd_range (old_glyph);
+      unsigned fd = last_range.first;
       set.add (fd);
 
       if (fd != prev_fd)