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