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.hh"
  28 #include "hb-ot-glyf-table.hh"
  29 #include "hb-set.h"
  30 #include "hb-subset-glyf.hh"
  31
  32 struct loca_data_t
  33 {
  34   bool          is_short;
  35   void         *data;
  36   unsigned int  size;
  37
  38   inline bool
  39   _write_loca_entry (unsigned int  id,
  40                      unsigned int  offset)
  41   {
  42     unsigned int entry_size = is_short ? sizeof (OT::HBUINT16) : sizeof (OT::HBUINT32);
  43     if ((id + 1) * entry_size <= size)
  44     {
  45       if (is_short) {
  46         ((OT::HBUINT16*) data) [id].set (offset / 2);
  47       } else {
  48         ((OT::HBUINT32*) data) [id].set (offset);
  49       }
  50       return true;
  51     }
  52
  53     // Offset was not written because the write is out of bounds.
  54     DEBUG_MSG(SUBSET,
  55               nullptr,
  56               "WARNING: Attempted to write an out of bounds loca entry at index %d. Loca size is %d.",
  57               id,
  58               size);
  59     return false;
  60   }
  61 };
  62
  63 /**
  64  * If hints are being dropped find the range which in glyf at which
  65  * the hinting instructions are located. Add them to the instruction_ranges
  66  * vector.
  67  */
  68 static bool
  69 _add_instructions_range (const OT::glyf::accelerator_t &glyf,
  70                          hb_codepoint_t                 glyph_id,
  71                          unsigned int                   glyph_start_offset,
  72                          unsigned int                   glyph_end_offset,
  73                          bool                           drop_hints,
  74                          hb_vector_t<unsigned int>     *instruction_ranges /* OUT */)
  75 {
  76   if (!instruction_ranges->resize (instruction_ranges->length + 2))
  77   {
  78     DEBUG_MSG(SUBSET, nullptr, "Failed to resize instruction_ranges.");
  79     return false;
  80   }
  81   unsigned int *instruction_start = &(*instruction_ranges)[instruction_ranges->length - 2];
  82   *instruction_start = 0;
  83   unsigned int *instruction_end = &(*instruction_ranges)[instruction_ranges->length - 1];
  84   *instruction_end = 0;
  85
  86   if (drop_hints)
  87   {
  88     if (unlikely (!glyf.get_instruction_offsets (glyph_start_offset, glyph_end_offset,
  89                                                  instruction_start, instruction_end)))
  90     {
  91       DEBUG_MSG(SUBSET, nullptr, "Unable to get instruction offsets for %d", glyph_id);
  92       return false;
  93     }
  94   }
  95
  96   return true;
  97 }
  98
  99 static bool
 100 _calculate_glyf_and_loca_prime_size (const OT::glyf::accelerator_t &glyf,
 101                                      const hb_subset_plan_t        *plan,
 102                                      loca_data_t                   *loca_data, /* OUT */
 103                                      unsigned int                  *glyf_size /* OUT */,
 104                                      hb_vector_t<unsigned int>     *instruction_ranges /* OUT */)
 105 {
 106   unsigned int total = 0;
 107
 108   hb_codepoint_t next_glyph = HB_SET_VALUE_INVALID;
 109   while (plan->glyphset ()->next (&next_glyph))
 110   {
 111     unsigned int start_offset, end_offset;
 112     if (unlikely (!(glyf.get_offsets (next_glyph, &start_offset, &end_offset) &&
 113                     glyf.remove_padding (start_offset, &end_offset))))
 114     {
 115       DEBUG_MSG(SUBSET, nullptr, "Invalid gid %d", next_glyph);
 116       start_offset = end_offset = 0;
 117     }
 118
 119     bool is_zero_length = end_offset - start_offset < OT::glyf::GlyphHeader::static_size;
 120     if (!_add_instructions_range (glyf,
 121                                   next_glyph,
 122                                   start_offset,
 123                                   end_offset,
 124                                   plan->drop_hints && !is_zero_length,
 125                                   instruction_ranges))
 126       return false;
 127
 128     if (is_zero_length)
 129       continue; /* 0-length glyph */
 130
 131     total += end_offset - start_offset
 132              - ((*instruction_ranges)[instruction_ranges->length - 1]
 133                 - (*instruction_ranges)[instruction_ranges->length - 2]);
 134     /* round2 so short loca will work */
 135     total += total % 2;
 136   }
 137
 138   *glyf_size = total;
 139   loca_data->is_short = (total <= 131070);
 140   loca_data->size = (plan->num_output_glyphs () + 1)
 141       * (loca_data->is_short ? sizeof (OT::HBUINT16) : sizeof (OT::HBUINT32));
 142
 143   DEBUG_MSG(SUBSET, nullptr, "preparing to subset glyf: final size %d, loca size %d, using %s loca",
 144             total,
 145             loca_data->size,
 146             loca_data->is_short ? "short" : "long");
 147   return true;
 148 }
 149
 150 static void
 151 _update_components (const hb_subset_plan_t *plan,
 152                     char                   *glyph_start,
 153                     unsigned int            length)
 154 {
 155   OT::glyf::CompositeGlyphHeader::Iterator iterator;
 156   if (OT::glyf::CompositeGlyphHeader::get_iterator (glyph_start,
 157                                                     length,
 158                                                     &iterator))
 159   {
 160     do
 161     {
 162       hb_codepoint_t new_gid;
 163       if (!plan->new_gid_for_old_gid (iterator.current->glyphIndex,
 164                                       &new_gid))
 165         continue;
 166
 167       ((OT::glyf::CompositeGlyphHeader *) iterator.current)->glyphIndex.set (new_gid);
 168     } while (iterator.move_to_next ());
 169   }
 170 }
 171
 172 static bool _remove_composite_instruction_flag (char *glyf_prime, unsigned int length)
 173 {
 174   /* remove WE_HAVE_INSTRUCTIONS from flags in dest */
 175   OT::glyf::CompositeGlyphHeader::Iterator composite_it;
 176   if (unlikely (!OT::glyf::CompositeGlyphHeader::get_iterator (glyf_prime, length, &composite_it))) return false;
 177   const OT::glyf::CompositeGlyphHeader *glyph;
 178   do {
 179     glyph = composite_it.current;
 180     OT::HBUINT16 *flags = const_cast<OT::HBUINT16 *> (&glyph->flags);
 181     flags->set ( (uint16_t) *flags & ~OT::glyf::CompositeGlyphHeader::WE_HAVE_INSTRUCTIONS);
 182   } while (composite_it.move_to_next ());
 183   return true;
 184 }
 185
 186 static bool
 187 _write_glyf_and_loca_prime (const hb_subset_plan_t        *plan,
 188                             const OT::glyf::accelerator_t &glyf,
 189                             const char                    *glyf_data,
 190                             hb_vector_t<unsigned int>     &instruction_ranges,
 191                             unsigned int                   glyf_prime_size,
 192                             char                          *glyf_prime_data /* OUT */,
 193                             loca_data_t                   *loca_prime /* OUT */)
 194 {
 195   char *glyf_prime_data_next = glyf_prime_data;
 196
 197   bool success = true;
 198
 199
 200   unsigned int i = 0;
 201   hb_codepoint_t new_gid;
 202   for (new_gid = 0; new_gid < plan->num_output_glyphs (); new_gid++)
 203   {
 204     hb_codepoint_t old_gid;
 205     if (!plan->old_gid_for_new_gid (new_gid, &old_gid))
 206     {
 207       // Empty glyph, add a loca entry and carry on.
 208       loca_prime->_write_loca_entry (new_gid,
 209                                      glyf_prime_data_next - glyf_prime_data);
 210       continue;
 211     }
 212
 213
 214     unsigned int start_offset, end_offset;
 215     if (unlikely (!(glyf.get_offsets (old_gid, &start_offset, &end_offset) &&
 216                     glyf.remove_padding (start_offset, &end_offset))))
 217       end_offset = start_offset = 0;
 218
 219     unsigned int instruction_start = instruction_ranges[i * 2];
 220     unsigned int instruction_end = instruction_ranges[i * 2 + 1];
 221
 222     int length = end_offset - start_offset - (instruction_end - instruction_start);
 223
 224     if (glyf_prime_data_next + length > glyf_prime_data + glyf_prime_size)
 225     {
 226       DEBUG_MSG(SUBSET,
 227                 nullptr,
 228                 "WARNING: Attempted to write an out of bounds glyph entry for gid %d (length %d)",
 229                 i, length);
 230       return false;
 231     }
 232
 233     if (instruction_start == instruction_end)
 234       memcpy (glyf_prime_data_next, glyf_data + start_offset, length);
 235     else
 236     {
 237       memcpy (glyf_prime_data_next, glyf_data + start_offset, instruction_start - start_offset);
 238       memcpy (glyf_prime_data_next + instruction_start - start_offset, glyf_data + instruction_end, end_offset - instruction_end);
 239       /* if the instructions end at the end this was a composite glyph, else simple */
 240       if (instruction_end == end_offset)
 241       {
 242         if (unlikely (!_remove_composite_instruction_flag (glyf_prime_data_next, length))) return false;
 243       }
 244       else
 245         /* zero instruction length, which is just before instruction_start */
 246         memset (glyf_prime_data_next + instruction_start - start_offset - 2, 0, 2);
 247     }
 248
 249     success = success && loca_prime->_write_loca_entry (new_gid,
 250                                                         glyf_prime_data_next - glyf_prime_data);
 251     _update_components (plan, glyf_prime_data_next, length);
 252
 253     // TODO: don't align to two bytes if using long loca.
 254     glyf_prime_data_next += length + (length % 2); // Align to 2 bytes for short loca.
 255
 256     i++;
 257   }
 258
 259   // loca table has n+1 entries where the last entry signifies the end location of the last
 260   // glyph.
 261   success = success && loca_prime->_write_loca_entry (new_gid,
 262                                                       glyf_prime_data_next - glyf_prime_data);
 263   return success;
 264 }
 265
 266 static bool
 267 _hb_subset_glyf_and_loca (const OT::glyf::accelerator_t  &glyf,
 268                           const char                     *glyf_data,
 269                           hb_subset_plan_t               *plan,
 270                           bool                           *use_short_loca,
 271                           hb_blob_t                     **glyf_prime_blob /* OUT */,
 272                           hb_blob_t                     **loca_prime_blob /* OUT */)
 273 {
 274   // TODO(grieger): Sanity check allocation size for the new table.
 275   loca_data_t loca_prime;
 276   unsigned int glyf_prime_size;
 277   hb_vector_t<unsigned int> instruction_ranges;
 278   instruction_ranges.init ();
 279
 280   if (unlikely (!_calculate_glyf_and_loca_prime_size (glyf,
 281                                                       plan,
 282                                                       &loca_prime,
 283                                                       &glyf_prime_size,
 284                                                       &instruction_ranges))) {
 285     instruction_ranges.fini ();
 286     return false;
 287   }
 288   *use_short_loca = loca_prime.is_short;
 289
 290   char *glyf_prime_data = (char *) calloc (1, glyf_prime_size);
 291   loca_prime.data = (void *) calloc (1, loca_prime.size);
 292   if (unlikely (!_write_glyf_and_loca_prime (plan, glyf, glyf_data,
 293                                              instruction_ranges,
 294                                              glyf_prime_size, glyf_prime_data,
 295                                              &loca_prime))) {
 296     free (glyf_prime_data);
 297     free (loca_prime.data);
 298     instruction_ranges.fini ();
 299     return false;
 300   }
 301   instruction_ranges.fini ();
 302
 303   *glyf_prime_blob = hb_blob_create (glyf_prime_data,
 304                                      glyf_prime_size,
 305                                      HB_MEMORY_MODE_READONLY,
 306                                      glyf_prime_data,
 307                                      free);
 308   *loca_prime_blob = hb_blob_create ((char *) loca_prime.data,
 309                                      loca_prime.size,
 310                                      HB_MEMORY_MODE_READONLY,
 311                                      loca_prime.data,
 312                                      free);
 313   return true;
 314 }
 315
 316 /**
 317  * hb_subset_glyf:
 318  * Subsets the glyph table according to a provided plan.
 319  *
 320  * Return value: subsetted glyf table.
 321  *
 322  * Since: 1.7.5
 323  **/
 324 bool
 325 hb_subset_glyf_and_loca (hb_subset_plan_t *plan,
 326                          bool             *use_short_loca, /* OUT */
 327                          hb_blob_t       **glyf_prime, /* OUT */
 328                          hb_blob_t       **loca_prime /* OUT */)
 329 {
 330   hb_blob_t *glyf_blob = hb_sanitize_context_t ().reference_table<OT::glyf> (plan->source);
 331   const char *glyf_data = hb_blob_get_data (glyf_blob, nullptr);
 332
 333   OT::glyf::accelerator_t glyf;
 334   glyf.init (plan->source);
 335   bool result = _hb_subset_glyf_and_loca (glyf,
 336                                           glyf_data,
 337                                           plan,
 338                                           use_short_loca,
 339                                           glyf_prime,
 340                                           loca_prime);
 341
 342   hb_blob_destroy (glyf_blob);
 343   glyf.fini ();
 344
 345   return result;
 346 }