From 81e2db7cbcb87668c562329390a49d95a3a604bb Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 26 Jun 2023 14:17:44 -0600
Subject: [PATCH] [subset/cff1] Speed up plan_subset_charset

---
 src/hb-ot-cff-common.hh |  2 +-
 src/hb-ot-cff1-table.hh |  7 ++++---
 src/hb-subset-cff1.cc   | 13 ++++++++++++-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/hb-ot-cff-common.hh b/src/hb-ot-cff-common.hh
index f646425fd..43910a5f7 100644
--- a/src/hb-ot-cff-common.hh
+++ b/src/hb-ot-cff-common.hh
@@ -55,7 +55,7 @@ struct code_pair_t
 
 using str_buff_t = hb_vector_t<unsigned char>;
 using str_buff_vec_t = hb_vector_t<str_buff_t>;
-using glyph_to_sid_map_t = hb_vector_t<uint16_t>;
+using glyph_to_sid_map_t = hb_vector_t<code_pair_t>;
 
 /* CFF INDEX */
 template <typename COUNT>
diff --git a/src/hb-ot-cff1-table.hh b/src/hb-ot-cff1-table.hh
index 2118c4fb7..c5d7a9212 100644
--- a/src/hb-ot-cff1-table.hh
+++ b/src/hb-ot-cff1-table.hh
@@ -334,7 +334,7 @@ struct Charset0
   {
     mapping->resize (num_glyphs, false);
     for (hb_codepoint_t gid = 1; gid < num_glyphs; gid++)
-      mapping->arrayZ[gid] = sids[gid - 1];
+      mapping->arrayZ[gid] = {sids[gid - 1], gid + 1};
   }
 
   hb_codepoint_t get_glyph (hb_codepoint_t sid, unsigned int num_glyphs) const
@@ -440,8 +440,9 @@ struct Charset1_2 {
     {
       hb_codepoint_t sid = ranges[i].first;
       unsigned count = ranges[i].nLeft + 1;
+      unsigned last = gid + count;
       for (unsigned j = 0; j < count; j++)
-	mapping->arrayZ[gid++] = sid++;
+	mapping->arrayZ[gid++] = {sid++, last};
 
       if (gid >= num_glyphs)
         break;
@@ -1275,7 +1276,7 @@ struct cff1
 	auto *mapping = (glyph_to_sid_map_t *) hb_malloc (sizeof (glyph_to_sid_map_t));
 	if (unlikely (!mapping)) return nullptr;
 	mapping = new (mapping) glyph_to_sid_map_t ();
-	mapping->push (0);
+	mapping->push (code_pair_t {0, 1});
 	charset->collect_glyph_to_sid_map (mapping, num_glyphs);
 	return mapping;
       }
diff --git a/src/hb-subset-cff1.cc b/src/hb-subset-cff1.cc
index 018d2a105..07e72c9af 100644
--- a/src/hb-subset-cff1.cc
+++ b/src/hb-subset-cff1.cc
@@ -533,6 +533,7 @@ struct cff1_subset_plan
     if (it->first == 0) it++;
     auto _ = *it;
     bool not_is_cid = !acc.is_CID ();
+    bool skip = !not_is_cid && glyph_to_sid_map;
     if (not_is_cid)
       sidmap.alloc (num_glyphs);
     for (glyph = 1; glyph < num_glyphs; glyph++)
@@ -548,7 +549,11 @@ struct cff1_subset_plan
 	/* Retain the SID for the old missing glyph ID */
 	old_glyph = glyph;
       }
-      unsigned sid = glyph_to_sid_map ? glyph_to_sid_map->arrayZ[old_glyph] : acc.glyph_to_sid (old_glyph, &glyph_to_sid_cache);
+      unsigned sid;
+      if (glyph_to_sid_map)
+	sid = glyph_to_sid_map->arrayZ[old_glyph].code;
+      else
+        sid = acc.glyph_to_sid (old_glyph, &glyph_to_sid_cache);
 
       if (not_is_cid)
 	sid = sidmap.add (sid);
@@ -557,6 +562,12 @@ struct cff1_subset_plan
       {
 	code_pair_t pair { sid, glyph };
 	subset_charset_ranges.push (pair);
+
+	if (skip && glyph == old_glyph)
+	{
+	  glyph = hb_min (_.first - 1, glyph_to_sid_map->arrayZ[old_glyph].glyph - 1);
+	  sid += glyph - old_glyph;
+	}
       }
       last_sid = sid;
     }