src/hb-subset-glyf.cc

   1 /*
   2  * Copyright © 2018  Google, Inc.
   3  *
   4  *  This is part of HarfBuzz, a text shaping library.
   5  *
   6  * Permission is hereby granted, without written agreement and without
   7  * license or royalty fees, to use, copy, modify, and distribute this
   8  * software and its documentation for any purpose, provided that the
   9  * above copyright notice and the following two paragraphs appear in
  10  * all copies of this software.
  11  *
  12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  16  * DAMAGE.
  17  *
  18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  *
  24  * Google Author(s): Garret Rieger, Roderick Sheeter
  25  */
  26
  27 #include "hb-open-type-private.hh"
  28 #include "hb-ot-glyf-table.hh"
  29 #include "hb-set.h"
  30 #include "hb-subset-glyf.hh"
  31 #include "hb-subset-plan.hh"
  32
  33 static bool
  34 _calculate_glyf_and_loca_prime_size (const OT::glyf::accelerator_t &glyf,
  35                                      hb_prealloced_array_t<hb_codepoint_t> &glyph_ids,
  36                                      hb_bool_t drop_hints,
  37                                      bool *use_short_loca /* OUT */,
  38                                      unsigned int *glyf_size /* OUT */,
  39                                      unsigned int *loca_size /* OUT */,
  40                                      hb_prealloced_array_t<unsigned int> *instruction_ranges /* OUT */)
  41 {
  42   unsigned int total = 0;
  43   for (unsigned int i = 0; i < glyph_ids.len; i++)
  44   {
  45     hb_codepoint_t next_glyph = glyph_ids[i];
  46     unsigned int *instruction_start = instruction_ranges->push();
  47     unsigned int *instruction_end = instruction_ranges->push();
  48     *instruction_start = 0;
  49     *instruction_end = 0;
  50
  51     unsigned int start_offset, end_offset;
  52     if (unlikely (!(glyf.get_offsets(next_glyph, &start_offset, &end_offset)
  53                     && glyf.remove_padding(start_offset, &end_offset))))
  54     {
  55       DEBUG_MSG(SUBSET, nullptr, "Invalid gid %d", next_glyph);
  56       continue;
  57     }
  58     if (end_offset - start_offset < OT::glyf::GlyphHeader::static_size)
  59       continue; /* 0-length glyph */
  60
  61     if (drop_hints)
  62     {
  63       if (unlikely (!glyf.get_instruction_offsets(start_offset, end_offset,
  64                                                   instruction_start, instruction_end)))
  65       {
  66         DEBUG_MSG(SUBSET, nullptr, "Unable to get instruction offsets for %d", next_glyph);
  67         return false;
  68       }
  69     }
  70
  71     total += end_offset - start_offset - (*instruction_end - *instruction_start);
  72     /* round2 so short loca will work */
  73     total += total % 2;
  74   }
  75
  76   *glyf_size = total;
  77   *use_short_loca = (total <= 131070);
  78   *loca_size = (glyph_ids.len + 1)
  79       * (*use_short_loca ? sizeof(OT::HBUINT16) : sizeof(OT::HBUINT32));
  80
  81   DEBUG_MSG(SUBSET, nullptr, "preparing to subset glyf: final size %d, loca size %d, using %s loca",
  82             total,
  83             *loca_size,
  84             *use_short_loca ? "short" : "long");
  85   return true;
  86 }
  87
  88 static bool
  89 _write_loca_entry (unsigned int  id,
  90                    unsigned int  offset,
  91                    bool          is_short,
  92                    void         *loca_prime,
  93                    unsigned int  loca_size)
  94 {
  95   unsigned int entry_size = is_short ? sizeof (OT::HBUINT16) : sizeof (OT::HBUINT32);
  96   if ((id + 1) * entry_size <= loca_size)
  97   {
  98     if (is_short) {
  99       ((OT::HBUINT16*) loca_prime) [id].set (offset / 2);
 100     } else {
 101       ((OT::HBUINT32*) loca_prime) [id].set (offset);
 102     }
 103     return true;
 104   }
 105
 106   // Offset was not written because the write is out of bounds.
 107   DEBUG_MSG (SUBSET,
 108              nullptr,
 109              "WARNING: Attempted to write an out of bounds loca entry at index %d. Loca size is %d.",
 110              id,
 111              loca_size);
 112   return false;
 113 }
 114
 115 static void
 116 _update_components (hb_subset_plan_t * plan,
 117                     char * glyph_start,
 118                     unsigned int length)
 119
 120 {
 121   OT::glyf::CompositeGlyphHeader::Iterator iterator;
 122   if (OT::glyf::CompositeGlyphHeader::get_iterator (glyph_start,
 123                                                     length,
 124                                                     &iterator))
 125   {
 126     do
 127     {
 128       hb_codepoint_t new_gid;
 129       if (!hb_subset_plan_new_gid_for_old_id (plan,
 130                                               iterator.current->glyphIndex,
 131                                               &new_gid))
 132         continue;
 133
 134       ((OT::glyf::CompositeGlyphHeader *) iterator.current)->glyphIndex.set (new_gid);
 135     } while (iterator.move_to_next());
 136   }
 137 }
 138
 139 static bool _remove_composite_instruction_flag(char *glyf_prime, unsigned int length)
 140 {
 141   /* remove WE_HAVE_INSTRUCTIONS from flags in dest */
 142   OT::glyf::CompositeGlyphHeader::Iterator composite_it;
 143   if (unlikely (!OT::glyf::CompositeGlyphHeader::get_iterator (glyf_prime, length, &composite_it))) return false;
 144   const OT::glyf::CompositeGlyphHeader *glyph;
 145   do {
 146     glyph = composite_it.current;
 147     OT::HBUINT16 *flags = const_cast<OT::HBUINT16 *> (&glyph->flags);
 148     flags->set ( (uint16_t) *flags & ~OT::glyf::CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS);
 149   } while (composite_it.move_to_next());
 150   return true;
 151 }
 152
 153 static bool
 154 _write_glyf_and_loca_prime (hb_subset_plan_t              *plan,
 155                             const OT::glyf::accelerator_t &glyf,
 156                             const char                    *glyf_data,
 157                             bool                           use_short_loca,
 158                             hb_prealloced_array_t<unsigned int> &instruction_ranges,
 159                             unsigned int                   glyf_prime_size,
 160                             char                          *glyf_prime_data /* OUT */,
 161                             unsigned int                   loca_prime_size,
 162                             char                          *loca_prime_data /* OUT */)
 163 {
 164   hb_prealloced_array_t<hb_codepoint_t> &glyph_ids = plan->gids_to_retain_sorted;
 165   char *glyf_prime_data_next = glyf_prime_data;
 166
 167   bool success = true;
 168   for (unsigned int i = 0; i < glyph_ids.len; i++)
 169   {
 170     unsigned int start_offset, end_offset;
 171     if (unlikely (!(glyf.get_offsets (glyph_ids[i], &start_offset, &end_offset)
 172                     && glyf.remove_padding(start_offset, &end_offset))))
 173       end_offset = start_offset = 0;
 174     unsigned int instruction_start = instruction_ranges[i * 2];
 175     unsigned int instruction_end = instruction_ranges[i * 2 + 1];
 176
 177     int length = end_offset - start_offset - (instruction_end - instruction_start);
 178     length += length % 2;
 179
 180     if (glyf_prime_data_next + length > glyf_prime_data + glyf_prime_size)
 181     {
 182       DEBUG_MSG (SUBSET,
 183                  nullptr,
 184                  "WARNING: Attempted to write an out of bounds glyph entry for gid %d (length %d)",
 185                  i, length);
 186       return false;
 187     }
 188
 189     if (instruction_start == instruction_end)
 190       memcpy (glyf_prime_data_next, glyf_data + start_offset, length);
 191     else
 192     {
 193       memcpy (glyf_prime_data_next, glyf_data + start_offset, instruction_start - start_offset);
 194       memcpy (glyf_prime_data_next + instruction_start - start_offset, glyf_data + instruction_end, end_offset - instruction_end);
 195       /* if the instructions end at the end this was a composite glyph, else simple */
 196       if (instruction_end == end_offset)
 197       {
 198         if (unlikely (!_remove_composite_instruction_flag (glyf_prime_data_next, length))) return false;
 199       }
 200       else
 201         /* zero instruction length, which is just before instruction_start */
 202         memset (glyf_prime_data_next + instruction_start - start_offset - 2, 0, 2);
 203     }
 204
 205     success = success && _write_loca_entry (i,
 206                                             glyf_prime_data_next - glyf_prime_data,
 207                                             use_short_loca,
 208                                             loca_prime_data,
 209                                             loca_prime_size);
 210     _update_components (plan, glyf_prime_data_next, length);
 211
 212     glyf_prime_data_next += length;
 213   }
 214
 215   success = success && _write_loca_entry (glyph_ids.len,
 216                                           glyf_prime_data_next - glyf_prime_data,
 217                                           use_short_loca,
 218                                           loca_prime_data,
 219                                           loca_prime_size);
 220   return success;
 221 }
 222
 223 static bool
 224 _hb_subset_glyf_and_loca (const OT::glyf::accelerator_t  &glyf,
 225                           const char                     *glyf_data,
 226                           hb_subset_plan_t               *plan,
 227                           bool                           *use_short_loca,
 228                           hb_blob_t                     **glyf_prime /* OUT */,
 229                           hb_blob_t                     **loca_prime /* OUT */)
 230 {
 231   // TODO(grieger): Sanity check allocation size for the new table.
 232   hb_prealloced_array_t<hb_codepoint_t> &glyphs_to_retain = plan->gids_to_retain_sorted;
 233
 234   unsigned int glyf_prime_size;
 235   unsigned int loca_prime_size;
 236   hb_prealloced_array_t<unsigned int> instruction_ranges;
 237   instruction_ranges.init();
 238
 239   if (unlikely (!_calculate_glyf_and_loca_prime_size (glyf,
 240                                                       glyphs_to_retain,
 241                                                       plan->drop_hints,
 242                                                       use_short_loca,
 243                                                       &glyf_prime_size,
 244                                                       &loca_prime_size,
 245                                                       &instruction_ranges))) {
 246     instruction_ranges.finish();
 247     return false;
 248   }
 249
 250   char *glyf_prime_data = (char *) calloc (1, glyf_prime_size);
 251   char *loca_prime_data = (char *) calloc (1, loca_prime_size);
 252   if (unlikely (!_write_glyf_and_loca_prime (plan, glyf, glyf_data,
 253                                              *use_short_loca,
 254                                              instruction_ranges,
 255                                              glyf_prime_size, glyf_prime_data,
 256                                              loca_prime_size, loca_prime_data))) {
 257     free (glyf_prime_data);
 258     free (loca_prime_data);
 259     instruction_ranges.finish();
 260     return false;
 261   }
 262   instruction_ranges.finish();
 263
 264   *glyf_prime = hb_blob_create (glyf_prime_data,
 265                                 glyf_prime_size,
 266                                 HB_MEMORY_MODE_READONLY,
 267                                 glyf_prime_data,
 268                                 free);
 269   *loca_prime = hb_blob_create (loca_prime_data,
 270                                 loca_prime_size,
 271                                 HB_MEMORY_MODE_READONLY,
 272                                 loca_prime_data,
 273                                 free);
 274   return true;
 275 }
 276
 277 /**
 278  * hb_subset_glyf:
 279  * Subsets the glyph table according to a provided plan.
 280  *
 281  * Return value: subsetted glyf table.
 282  *
 283  * Since: 1.7.5
 284  **/
 285 bool
 286 hb_subset_glyf_and_loca (hb_subset_plan_t *plan,
 287                          bool             *use_short_loca, /* OUT */
 288                          hb_blob_t       **glyf_prime, /* OUT */
 289                          hb_blob_t       **loca_prime /* OUT */)
 290 {
 291   hb_blob_t *glyf_blob = OT::Sanitizer<OT::glyf>().sanitize (plan->source->reference_table (HB_OT_TAG_glyf));
 292   const char *glyf_data = hb_blob_get_data(glyf_blob, nullptr);
 293
 294   OT::glyf::accelerator_t glyf;
 295   glyf.init(plan->source);
 296   bool result = _hb_subset_glyf_and_loca (glyf,
 297                                           glyf_data,
 298                                           plan,
 299                                           use_short_loca,
 300                                           glyf_prime,
 301                                           loca_prime);
 302
 303   hb_blob_destroy (glyf_blob);
 304   glyf.fini();
 305
 306   return result;
 307 }