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