DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (fce0b326cd31)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357
// Copyright (c) 2009-2017 The OTS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "glyf.h"

#include <algorithm>
#include <limits>

#include "head.h"
#include "loca.h"
#include "maxp.h"

// glyf - Glyph Data
// http://www.microsoft.com/typography/otspec/glyf.htm

namespace ots {

bool OpenTypeGLYF::ParseFlagsForSimpleGlyph(Buffer &glyph,
                                            uint32_t num_flags,
                                            uint32_t *flag_index,
                                            uint32_t *coordinates_length) {
  uint8_t flag = 0;
  if (!glyph.ReadU8(&flag)) {
    return Error("Can't read flag");
  }

  uint32_t delta = 0;
  if (flag & (1u << 1)) {  // x-Short
    ++delta;
  } else if (!(flag & (1u << 4))) {
    delta += 2;
  }

  if (flag & (1u << 2)) {  // y-Short
    ++delta;
  } else if (!(flag & (1u << 5))) {
    delta += 2;
  }

  /* MS and Apple specs say this bit is reserved and must be set to zero, but
   * Apple spec then contradicts itself and says it should be set on the first
   * contour flag for simple glyphs with overlapping contours:
   * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6AATIntro.html
   * (“Overlapping contours” section) */
  if (flag & (1u << 6) && *flag_index != 0) {
    return Error("Bad glyph flag (%d), "
                 "bit 6 must be set to zero for flag %d", flag, *flag_index);
  }

  if (flag & (1u << 3)) {  // repeat
    if (*flag_index + 1 >= num_flags) {
      return Error("Count too high (%d + 1 >= %d)", *flag_index, num_flags);
    }
    uint8_t repeat = 0;
    if (!glyph.ReadU8(&repeat)) {
      return Error("Can't read repeat value");
    }
    if (repeat == 0) {
      return Error("Zero repeat");
    }
    delta += (delta * repeat);

    *flag_index += repeat;
    if (*flag_index >= num_flags) {
      return Error("Count too high (%d >= %d)", *flag_index, num_flags);
    }
  }

  if (flag & (1u << 7)) {  // reserved flag
    return Error("Bad glyph flag (%d), reserved bit 7 must be set to zero", flag);
  }

  *coordinates_length += delta;
  if (glyph.length() < *coordinates_length) {
    return Error("Glyph coordinates length bigger than glyph length (%d > %d)",
                 *coordinates_length, glyph.length());
  }

  return true;
}

bool OpenTypeGLYF::ParseSimpleGlyph(Buffer &glyph,
                                    int16_t num_contours) {
  // read the end-points array
  uint16_t num_flags = 0;
  for (int i = 0; i < num_contours; ++i) {
    uint16_t tmp_index = 0;
    if (!glyph.ReadU16(&tmp_index)) {
      return Error("Can't read contour index %d", i);
    }
    if (tmp_index == 0xffffu) {
      return Error("Bad contour index %d", i);
    }
    // check if the indices are monotonically increasing
    if (i && (tmp_index + 1 <= num_flags)) {
      return Error("Decreasing contour index %d + 1 <= %d", tmp_index, num_flags);
    }
    num_flags = tmp_index + 1;
  }

  uint16_t bytecode_length = 0;
  if (!glyph.ReadU16(&bytecode_length)) {
    return Error("Can't read bytecode length");
  }

  if (this->maxp->version_1 &&
      this->maxp->max_size_glyf_instructions < bytecode_length) {
    this->maxp->max_size_glyf_instructions = bytecode_length;
    Warning("Bytecode length is bigger than maxp.maxSizeOfInstructions %d: %d",
            this->maxp->max_size_glyf_instructions, bytecode_length);
  }

  if (!glyph.Skip(bytecode_length)) {
    return Error("Can't read bytecode of length %d", bytecode_length);
  }

  uint32_t coordinates_length = 0;
  for (uint32_t i = 0; i < num_flags; ++i) {
    if (!ParseFlagsForSimpleGlyph(glyph, num_flags, &i, &coordinates_length)) {
      return Error("Failed to parse glyph flags %d", i);
    }
  }

  if (!glyph.Skip(coordinates_length)) {
    return Error("Glyph too short %d", glyph.length());
  }

  if (glyph.remaining() > 3) {
    // We allow 0-3 bytes difference since gly_length is 4-bytes aligned,
    // zero-padded length.
    Warning("Extra bytes at end of the glyph: %d", glyph.remaining());
  }

  this->iov.push_back(std::make_pair(glyph.buffer(), glyph.offset()));

  return true;
}

#define ARG_1_AND_2_ARE_WORDS    (1u << 0)
#define WE_HAVE_A_SCALE          (1u << 3)
#define MORE_COMPONENTS          (1u << 5)
#define WE_HAVE_AN_X_AND_Y_SCALE (1u << 6)
#define WE_HAVE_A_TWO_BY_TWO     (1u << 7)
#define WE_HAVE_INSTRUCTIONS     (1u << 8)

bool OpenTypeGLYF::ParseCompositeGlyph(Buffer &glyph) {
  uint16_t flags = 0;
  uint16_t gid = 0;
  do {
    if (!glyph.ReadU16(&flags) || !glyph.ReadU16(&gid)) {
      return Error("Can't read composite glyph flags or glyphIndex");
    }

    if (gid >= this->maxp->num_glyphs) {
      return Error("Invalid glyph id used in composite glyph: %d", gid);
    }

    if (flags & ARG_1_AND_2_ARE_WORDS) {
      int16_t argument1;
      int16_t argument2;
      if (!glyph.ReadS16(&argument1) || !glyph.ReadS16(&argument2)) {
        return Error("Can't read argument1 or argument2");
      }
    } else {
      uint8_t argument1;
      uint8_t argument2;
      if (!glyph.ReadU8(&argument1) || !glyph.ReadU8(&argument2)) {
        return Error("Can't read argument1 or argument2");
      }
    }

    if (flags & WE_HAVE_A_SCALE) {
      int16_t scale;
      if (!glyph.ReadS16(&scale)) {
        return Error("Can't read scale");
      }
    } else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) {
      int16_t xscale;
      int16_t yscale;
      if (!glyph.ReadS16(&xscale) || !glyph.ReadS16(&yscale)) {
        return Error("Can't read xscale or yscale");
      }
    } else if (flags & WE_HAVE_A_TWO_BY_TWO) {
      int16_t xscale;
      int16_t scale01;
      int16_t scale10;
      int16_t yscale;
      if (!glyph.ReadS16(&xscale) ||
          !glyph.ReadS16(&scale01) ||
          !glyph.ReadS16(&scale10) ||
          !glyph.ReadS16(&yscale)) {
        return Error("Can't read transform");
      }
    }
  } while (flags & MORE_COMPONENTS);

  if (flags & WE_HAVE_INSTRUCTIONS) {
    uint16_t bytecode_length;
    if (!glyph.ReadU16(&bytecode_length)) {
      return Error("Can't read instructions size");
    }

    if (this->maxp->version_1 &&
        this->maxp->max_size_glyf_instructions < bytecode_length) {
      this->maxp->max_size_glyf_instructions = bytecode_length;
      Warning("Bytecode length is bigger than maxp.maxSizeOfInstructions "
              "%d: %d",
              this->maxp->max_size_glyf_instructions, bytecode_length);
    }

    if (!glyph.Skip(bytecode_length)) {
      return Error("Can't read bytecode of length %d", bytecode_length);
    }
  }

  this->iov.push_back(std::make_pair(glyph.buffer(), glyph.offset()));

  return true;
}

bool OpenTypeGLYF::Parse(const uint8_t *data, size_t length) {
  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
      GetFont()->GetTypedTable(OTS_TAG_MAXP));
  OpenTypeLOCA *loca = static_cast<OpenTypeLOCA*>(
      GetFont()->GetTypedTable(OTS_TAG_LOCA));
  OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(
      GetFont()->GetTypedTable(OTS_TAG_HEAD));
  if (!maxp || !loca || !head) {
    return Error("Missing maxp or loca or head table needed by glyf table");
  }

  this->maxp = maxp;

  const unsigned num_glyphs = maxp->num_glyphs;
  std::vector<uint32_t> &offsets = loca->offsets;

  if (offsets.size() != num_glyphs + 1) {
    return Error("Invalide glyph offsets size %ld != %d", offsets.size(), num_glyphs + 1);
  }

  std::vector<uint32_t> resulting_offsets(num_glyphs + 1);
  uint32_t current_offset = 0;

  for (unsigned i = 0; i < num_glyphs; ++i) {
    const unsigned gly_offset = offsets[i];
    // The LOCA parser checks that these values are monotonic
    const unsigned gly_length = offsets[i + 1] - offsets[i];
    if (!gly_length) {
      // this glyph has no outline (e.g. the space charactor)
      resulting_offsets[i] = current_offset;
      continue;
    }

    if (gly_offset >= length) {
      return Error("Glyph %d offset %d too high %ld", i, gly_offset, length);
    }
    // Since these are unsigned types, the compiler is not allowed to assume
    // that they never overflow.
    if (gly_offset + gly_length < gly_offset) {
      return Error("Glyph %d length (%d < 0)!", i, gly_length);
    }
    if (gly_offset + gly_length > length) {
      return Error("Glyph %d length %d too high", i, gly_length);
    }

    Buffer glyph(data + gly_offset, gly_length);

    int16_t num_contours, xmin, ymin, xmax, ymax;
    if (!glyph.ReadS16(&num_contours) ||
        !glyph.ReadS16(&xmin) ||
        !glyph.ReadS16(&ymin) ||
        !glyph.ReadS16(&xmax) ||
        !glyph.ReadS16(&ymax)) {
      return Error("Can't read glyph %d header", i);
    }

    if (num_contours <= -2) {
      // -2, -3, -4, ... are reserved for future use.
      return Error("Bad number of contours %d in glyph %d", num_contours, i);
    }

    // workaround for fonts in http://www.princexml.com/fonts/
    if ((xmin == 32767) &&
        (xmax == -32767) &&
        (ymin == 32767) &&
        (ymax == -32767)) {
      Warning("bad xmin/xmax/ymin/ymax values");
      xmin = xmax = ymin = ymax = 0;
    }

    if (xmin > xmax || ymin > ymax) {
      return Error("Bad bounding box values bl=(%d, %d), tr=(%d, %d) in glyph %d", xmin, ymin, xmax, ymax, i);
    }

    if (num_contours == 0) {
      // This is an empty glyph and shouldn’t have any glyph data, but if it
      // does we will simply ignore it.
      glyph.set_offset(0);
    } else if (num_contours > 0) {
      if (!ParseSimpleGlyph(glyph, num_contours)) {
        return Error("Failed to parse glyph %d", i);
      }
    } else {
      if (!ParseCompositeGlyph(glyph)) {
        return Error("Failed to parse glyph %d", i);
      }
    }

    size_t new_size = glyph.offset();
    resulting_offsets[i] = current_offset;
    // glyphs must be four byte aligned
    // TODO(yusukes): investigate whether this padding is really necessary.
    //                Which part of the spec requires this?
    const unsigned padding = (4 - (new_size & 3)) % 4;
    if (padding) {
      this->iov.push_back(std::make_pair(
          reinterpret_cast<const uint8_t*>("\x00\x00\x00\x00"),
          static_cast<size_t>(padding)));
      new_size += padding;
    }
    current_offset += new_size;
  }
  resulting_offsets[num_glyphs] = current_offset;

  const uint16_t max16 = std::numeric_limits<uint16_t>::max();
  if ((*std::max_element(resulting_offsets.begin(),
                         resulting_offsets.end()) >= (max16 * 2u)) &&
      (head->index_to_loc_format != 1)) {
    head->index_to_loc_format = 1;
  }

  loca->offsets = resulting_offsets;

  if (this->iov.empty()) {
    // As a special case when all glyph in the font are empty, add a zero byte
    // to the table, so that we don’t reject it down the way, and to make the
    // table work on Windows as well.
    // See https://github.com/khaledhosny/ots/issues/52
    static const uint8_t kZero = 0;
    this->iov.push_back(std::make_pair(&kZero, 1));
  }

  return true;
}

bool OpenTypeGLYF::Serialize(OTSStream *out) {
  for (unsigned i = 0; i < this->iov.size(); ++i) {
    if (!out->Write(this->iov[i].first, this->iov[i].second)) {
      return Error("Falied to write glyph %d", i);
    }
  }

  return true;
}

}  // namespace ots