third_party/ots/src/math.cc

   1 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // We use an underscore to avoid confusion with the standard math.h library.
   6 #include "math_.h"
   7
   8 #include <limits>
   9 #include <vector>
  10
  11 #include "layout.h"
  12 #include "maxp.h"
  13
  14 // MATH - The MATH Table
  15 // The specification is not yet public but has been submitted to the MPEG group
  16 // in response to the 'Call for Proposals for ISO/IEC 14496-22 "Open Font
  17 // Format" Color Font Technology and MATH layout support'. Meanwhile, you can
  18 // contact Microsoft's engineer Murray Sargent to obtain a copy.
  19
  20 #define TABLE_NAME "MATH"
  21
  22 namespace {
  23
  24 // The size of MATH header.
  25 // Version
  26 // MathConstants
  27 // MathGlyphInfo
  28 // MathVariants
  29 const unsigned kMathHeaderSize = 4 + 3 * 2;
  30
  31 // The size of the MathGlyphInfo header.
  32 // MathItalicsCorrectionInfo
  33 // MathTopAccentAttachment
  34 // ExtendedShapeCoverage
  35 // MathKernInfo
  36 const unsigned kMathGlyphInfoHeaderSize = 4 * 2;
  37
  38 // The size of the MathValueRecord.
  39 // Value
  40 // DeviceTable
  41 const unsigned kMathValueRecordSize = 2 * 2;
  42
  43 // The size of the GlyphPartRecord.
  44 // glyph
  45 // StartConnectorLength
  46 // EndConnectorLength
  47 // FullAdvance
  48 // PartFlags
  49 const unsigned kGlyphPartRecordSize = 5 * 2;
  50
  51 // Shared Table: MathValueRecord
  52
  53 bool ParseMathValueRecord(const ots::Font *font,
  54                           ots::Buffer* subtable, const uint8_t *data,
  55                           const size_t length) {
  56   // Check the Value field.
  57   if (!subtable->Skip(2)) {
  58     return OTS_FAILURE();
  59   }
  60
  61   // Check the offset to device table.
  62   uint16_t offset = 0;
  63   if (!subtable->ReadU16(&offset)) {
  64     return OTS_FAILURE();
  65   }
  66   if (offset) {
  67     if (offset >= length) {
  68       return OTS_FAILURE();
  69     }
  70     if (!ots::ParseDeviceTable(font, data + offset, length - offset)) {
  71       return OTS_FAILURE();
  72     }
  73   }
  74
  75   return true;
  76 }
  77
  78 bool ParseMathConstantsTable(const ots::Font *font,
  79                              const uint8_t *data, size_t length) {
  80   ots::Buffer subtable(data, length);
  81
  82   // Part 1: int16 or uint16 constants.
  83   //  ScriptPercentScaleDown
  84   //  ScriptScriptPercentScaleDown
  85   //  DelimitedSubFormulaMinHeight
  86   //  DisplayOperatorMinHeight
  87   if (!subtable.Skip(4 * 2)) {
  88     return OTS_FAILURE();
  89   }
  90
  91   // Part 2: MathValueRecord constants.
  92   // MathLeading
  93   // AxisHeight
  94   // AccentBaseHeight
  95   // FlattenedAccentBaseHeight
  96   // SubscriptShiftDown
  97   // SubscriptTopMax
  98   // SubscriptBaselineDropMin
  99   // SuperscriptShiftUp
 100   // SuperscriptShiftUpCramped
 101   // SuperscriptBottomMin
 102   //
 103   // SuperscriptBaselineDropMax
 104   // SubSuperscriptGapMin
 105   // SuperscriptBottomMaxWithSubscript
 106   // SpaceAfterScript
 107   // UpperLimitGapMin
 108   // UpperLimitBaselineRiseMin
 109   // LowerLimitGapMin
 110   // LowerLimitBaselineDropMin
 111   // StackTopShiftUp
 112   // StackTopDisplayStyleShiftUp
 113   //
 114   // StackBottomShiftDown
 115   // StackBottomDisplayStyleShiftDown
 116   // StackGapMin
 117   // StackDisplayStyleGapMin
 118   // StretchStackTopShiftUp
 119   // StretchStackBottomShiftDown
 120   // StretchStackGapAboveMin
 121   // StretchStackGapBelowMin
 122   // FractionNumeratorShiftUp
 123   // FractionNumeratorDisplayStyleShiftUp
 124   //
 125   // FractionDenominatorShiftDown
 126   // FractionDenominatorDisplayStyleShiftDown
 127   // FractionNumeratorGapMin
 128   // FractionNumDisplayStyleGapMin
 129   // FractionRuleThickness
 130   // FractionDenominatorGapMin
 131   // FractionDenomDisplayStyleGapMin
 132   // SkewedFractionHorizontalGap
 133   // SkewedFractionVerticalGap
 134   // OverbarVerticalGap
 135   //
 136   // OverbarRuleThickness
 137   // OverbarExtraAscender
 138   // UnderbarVerticalGap
 139   // UnderbarRuleThickness
 140   // UnderbarExtraDescender
 141   // RadicalVerticalGap
 142   // RadicalDisplayStyleVerticalGap
 143   // RadicalRuleThickness
 144   // RadicalExtraAscender
 145   // RadicalKernBeforeDegree
 146   //
 147   // RadicalKernAfterDegree
 148   for (unsigned i = 0; i < static_cast<unsigned>(51); ++i) {
 149     if (!ParseMathValueRecord(font, &subtable, data, length)) {
 150       return OTS_FAILURE();
 151     }
 152   }
 153
 154   // Part 3: uint16 constant
 155   // RadicalDegreeBottomRaisePercent
 156   if (!subtable.Skip(2)) {
 157     return OTS_FAILURE();
 158   }
 159
 160   return true;
 161 }
 162
 163 bool ParseMathValueRecordSequenceForGlyphs(const ots::Font *font,
 164                                            ots::Buffer* subtable,
 165                                            const uint8_t *data,
 166                                            const size_t length,
 167                                            const uint16_t num_glyphs) {
 168   // Check the header.
 169   uint16_t offset_coverage = 0;
 170   uint16_t sequence_count = 0;
 171   if (!subtable->ReadU16(&offset_coverage) ||
 172       !subtable->ReadU16(&sequence_count)) {
 173     return OTS_FAILURE();
 174   }
 175
 176   const unsigned sequence_end = static_cast<unsigned>(2 * 2) +
 177       sequence_count * kMathValueRecordSize;
 178   if (sequence_end > std::numeric_limits<uint16_t>::max()) {
 179     return OTS_FAILURE();
 180   }
 181
 182   // Check coverage table.
 183   if (offset_coverage < sequence_end || offset_coverage >= length) {
 184     return OTS_FAILURE();
 185   }
 186   if (!ots::ParseCoverageTable(font, data + offset_coverage,
 187                                length - offset_coverage,
 188                                num_glyphs, sequence_count)) {
 189     return OTS_FAILURE();
 190   }
 191
 192   // Check sequence.
 193   for (unsigned i = 0; i < sequence_count; ++i) {
 194     if (!ParseMathValueRecord(font, subtable, data, length)) {
 195       return OTS_FAILURE();
 196     }
 197   }
 198
 199   return true;
 200 }
 201
 202 bool ParseMathItalicsCorrectionInfoTable(const ots::Font *font,
 203                                          const uint8_t *data,
 204                                          size_t length,
 205                                          const uint16_t num_glyphs) {
 206   ots::Buffer subtable(data, length);
 207   return ParseMathValueRecordSequenceForGlyphs(font, &subtable, data, length,
 208                                                num_glyphs);
 209 }
 210
 211 bool ParseMathTopAccentAttachmentTable(const ots::Font *font,
 212                                        const uint8_t *data,
 213                                        size_t length,
 214                                        const uint16_t num_glyphs) {
 215   ots::Buffer subtable(data, length);
 216   return ParseMathValueRecordSequenceForGlyphs(font, &subtable, data, length,
 217                                                num_glyphs);
 218 }
 219
 220 bool ParseMathKernTable(const ots::Font *font,
 221                         const uint8_t *data, size_t length) {
 222   ots::Buffer subtable(data, length);
 223
 224   // Check the Height count.
 225   uint16_t height_count = 0;
 226   if (!subtable.ReadU16(&height_count)) {
 227     return OTS_FAILURE();
 228   }
 229
 230   // Check the Correction Heights.
 231   for (unsigned i = 0; i < height_count; ++i) {
 232     if (!ParseMathValueRecord(font, &subtable, data, length)) {
 233       return OTS_FAILURE();
 234     }
 235   }
 236
 237   // Check the Kern Values.
 238   for (unsigned i = 0; i <= height_count; ++i) {
 239     if (!ParseMathValueRecord(font, &subtable, data, length)) {
 240       return OTS_FAILURE();
 241     }
 242   }
 243
 244   return true;
 245 }
 246
 247 bool ParseMathKernInfoTable(const ots::Font *font,
 248                             const uint8_t *data, size_t length,
 249                             const uint16_t num_glyphs) {
 250   ots::Buffer subtable(data, length);
 251
 252   // Check the header.
 253   uint16_t offset_coverage = 0;
 254   uint16_t sequence_count = 0;
 255   if (!subtable.ReadU16(&offset_coverage) ||
 256       !subtable.ReadU16(&sequence_count)) {
 257     return OTS_FAILURE();
 258   }
 259
 260   const unsigned sequence_end = static_cast<unsigned>(2 * 2) +
 261     sequence_count * 4 * 2;
 262   if (sequence_end > std::numeric_limits<uint16_t>::max()) {
 263     return OTS_FAILURE();
 264   }
 265
 266   // Check coverage table.
 267   if (offset_coverage < sequence_end || offset_coverage >= length) {
 268     return OTS_FAILURE();
 269   }
 270   if (!ots::ParseCoverageTable(font, data + offset_coverage, length - offset_coverage,
 271                                num_glyphs, sequence_count)) {
 272     return OTS_FAILURE();
 273   }
 274
 275   // Check sequence of MathKernInfoRecord
 276   for (unsigned i = 0; i < sequence_count; ++i) {
 277     // Check TopRight, TopLeft, BottomRight and BottomLeft Math Kern.
 278     for (unsigned j = 0; j < 4; ++j) {
 279       uint16_t offset_math_kern = 0;
 280       if (!subtable.ReadU16(&offset_math_kern)) {
 281         return OTS_FAILURE();
 282       }
 283       if (offset_math_kern) {
 284         if (offset_math_kern < sequence_end || offset_math_kern >= length ||
 285             !ParseMathKernTable(font, data + offset_math_kern,
 286                                 length - offset_math_kern)) {
 287           return OTS_FAILURE();
 288         }
 289       }
 290     }
 291   }
 292
 293   return true;
 294 }
 295
 296 bool ParseMathGlyphInfoTable(const ots::Font *font,
 297                              const uint8_t *data, size_t length,
 298                              const uint16_t num_glyphs) {
 299   ots::Buffer subtable(data, length);
 300
 301   // Check Header.
 302   uint16_t offset_math_italics_correction_info = 0;
 303   uint16_t offset_math_top_accent_attachment = 0;
 304   uint16_t offset_extended_shaped_coverage = 0;
 305   uint16_t offset_math_kern_info = 0;
 306   if (!subtable.ReadU16(&offset_math_italics_correction_info) ||
 307       !subtable.ReadU16(&offset_math_top_accent_attachment) ||
 308       !subtable.ReadU16(&offset_extended_shaped_coverage) ||
 309       !subtable.ReadU16(&offset_math_kern_info)) {
 310     return OTS_FAILURE();
 311   }
 312
 313   // Check subtables.
 314   // The specification does not say whether the offsets for
 315   // MathItalicsCorrectionInfo, MathTopAccentAttachment and MathKernInfo may
 316   // be NULL, but that's the case in some fonts (e.g STIX) so we accept that.
 317   if (offset_math_italics_correction_info) {
 318     if (offset_math_italics_correction_info >= length ||
 319         offset_math_italics_correction_info < kMathGlyphInfoHeaderSize ||
 320         !ParseMathItalicsCorrectionInfoTable(
 321             font, data + offset_math_italics_correction_info,
 322             length - offset_math_italics_correction_info,
 323             num_glyphs)) {
 324       return OTS_FAILURE();
 325     }
 326   }
 327   if (offset_math_top_accent_attachment) {
 328     if (offset_math_top_accent_attachment >= length ||
 329         offset_math_top_accent_attachment < kMathGlyphInfoHeaderSize ||
 330         !ParseMathTopAccentAttachmentTable(font, data +
 331                                            offset_math_top_accent_attachment,
 332                                            length -
 333                                            offset_math_top_accent_attachment,
 334                                            num_glyphs)) {
 335       return OTS_FAILURE();
 336     }
 337   }
 338   if (offset_extended_shaped_coverage) {
 339     if (offset_extended_shaped_coverage >= length ||
 340         offset_extended_shaped_coverage < kMathGlyphInfoHeaderSize ||
 341         !ots::ParseCoverageTable(font, data + offset_extended_shaped_coverage,
 342                                  length - offset_extended_shaped_coverage,
 343                                  num_glyphs)) {
 344       return OTS_FAILURE();
 345     }
 346   }
 347   if (offset_math_kern_info) {
 348     if (offset_math_kern_info >= length ||
 349         offset_math_kern_info < kMathGlyphInfoHeaderSize ||
 350         !ParseMathKernInfoTable(font, data + offset_math_kern_info,
 351                                 length - offset_math_kern_info, num_glyphs)) {
 352       return OTS_FAILURE();
 353     }
 354   }
 355
 356   return true;
 357 }
 358
 359 bool ParseGlyphAssemblyTable(const ots::Font *font,
 360                              const uint8_t *data,
 361                              size_t length, const uint16_t num_glyphs) {
 362   ots::Buffer subtable(data, length);
 363
 364   // Check the header.
 365   uint16_t part_count = 0;
 366   if (!ParseMathValueRecord(font, &subtable, data, length) ||
 367       !subtable.ReadU16(&part_count)) {
 368     return OTS_FAILURE();
 369   }
 370
 371   const unsigned sequence_end = kMathValueRecordSize +
 372     static_cast<unsigned>(2) + part_count * kGlyphPartRecordSize;
 373   if (sequence_end > std::numeric_limits<uint16_t>::max()) {
 374     return OTS_FAILURE();
 375   }
 376
 377   // Check the sequence of GlyphPartRecord.
 378   for (unsigned i = 0; i < part_count; ++i) {
 379     uint16_t glyph = 0;
 380     uint16_t part_flags = 0;
 381     if (!subtable.ReadU16(&glyph) ||
 382         !subtable.Skip(2 * 3) ||
 383         !subtable.ReadU16(&part_flags)) {
 384       return OTS_FAILURE();
 385     }
 386     if (glyph >= num_glyphs) {
 387       return OTS_FAILURE_MSG("bad glyph ID: %u", glyph);
 388     }
 389     if (part_flags & ~0x00000001) {
 390       return OTS_FAILURE_MSG("unknown part flag: %u", part_flags);
 391     }
 392   }
 393
 394   return true;
 395 }
 396
 397 bool ParseMathGlyphConstructionTable(const ots::Font *font,
 398                                      const uint8_t *data,
 399                                      size_t length, const uint16_t num_glyphs) {
 400   ots::Buffer subtable(data, length);
 401
 402   // Check the header.
 403   uint16_t offset_glyph_assembly = 0;
 404   uint16_t variant_count = 0;
 405   if (!subtable.ReadU16(&offset_glyph_assembly) ||
 406       !subtable.ReadU16(&variant_count)) {
 407     return OTS_FAILURE();
 408   }
 409
 410   const unsigned sequence_end = static_cast<unsigned>(2 * 2) +
 411     variant_count * 2 * 2;
 412   if (sequence_end > std::numeric_limits<uint16_t>::max()) {
 413     return OTS_FAILURE();
 414   }
 415
 416   // Check the GlyphAssembly offset.
 417   if (offset_glyph_assembly) {
 418     if (offset_glyph_assembly >= length ||
 419         offset_glyph_assembly < sequence_end) {
 420       return OTS_FAILURE();
 421     }
 422     if (!ParseGlyphAssemblyTable(font, data + offset_glyph_assembly,
 423                                  length - offset_glyph_assembly, num_glyphs)) {
 424       return OTS_FAILURE();
 425     }
 426   }
 427
 428   // Check the sequence of MathGlyphVariantRecord.
 429   for (unsigned i = 0; i < variant_count; ++i) {
 430     uint16_t glyph = 0;
 431     if (!subtable.ReadU16(&glyph) ||
 432         !subtable.Skip(2)) {
 433       return OTS_FAILURE();
 434     }
 435     if (glyph >= num_glyphs) {
 436       return OTS_FAILURE_MSG("bad glyph ID: %u", glyph);
 437     }
 438   }
 439
 440   return true;
 441 }
 442
 443 bool ParseMathGlyphConstructionSequence(const ots::Font *font,
 444                                         ots::Buffer* subtable,
 445                                         const uint8_t *data,
 446                                         size_t length,
 447                                         const uint16_t num_glyphs,
 448                                         uint16_t offset_coverage,
 449                                         uint16_t glyph_count,
 450                                         const unsigned sequence_end) {
 451   // Check coverage table.
 452   if (offset_coverage < sequence_end || offset_coverage >= length) {
 453     return OTS_FAILURE();
 454   }
 455   if (!ots::ParseCoverageTable(font, data + offset_coverage,
 456                                length - offset_coverage,
 457                                num_glyphs, glyph_count)) {
 458     return OTS_FAILURE();
 459   }
 460
 461   // Check sequence of MathGlyphConstruction.
 462   for (unsigned i = 0; i < glyph_count; ++i) {
 463       uint16_t offset_glyph_construction = 0;
 464       if (!subtable->ReadU16(&offset_glyph_construction)) {
 465         return OTS_FAILURE();
 466       }
 467       if (offset_glyph_construction < sequence_end ||
 468           offset_glyph_construction >= length ||
 469           !ParseMathGlyphConstructionTable(font, data + offset_glyph_construction,
 470                                            length - offset_glyph_construction,
 471                                            num_glyphs)) {
 472         return OTS_FAILURE();
 473       }
 474   }
 475
 476   return true;
 477 }
 478
 479 bool ParseMathVariantsTable(const ots::Font *font,
 480                             const uint8_t *data,
 481                             size_t length, const uint16_t num_glyphs) {
 482   ots::Buffer subtable(data, length);
 483
 484   // Check the header.
 485   uint16_t offset_vert_glyph_coverage = 0;
 486   uint16_t offset_horiz_glyph_coverage = 0;
 487   uint16_t vert_glyph_count = 0;
 488   uint16_t horiz_glyph_count = 0;
 489   if (!subtable.Skip(2) ||  // MinConnectorOverlap
 490       !subtable.ReadU16(&offset_vert_glyph_coverage) ||
 491       !subtable.ReadU16(&offset_horiz_glyph_coverage) ||
 492       !subtable.ReadU16(&vert_glyph_count) ||
 493       !subtable.ReadU16(&horiz_glyph_count)) {
 494     return OTS_FAILURE();
 495   }
 496
 497   const unsigned sequence_end = 5 * 2 + vert_glyph_count * 2 +
 498     horiz_glyph_count * 2;
 499   if (sequence_end > std::numeric_limits<uint16_t>::max()) {
 500     return OTS_FAILURE();
 501   }
 502
 503   if (!ParseMathGlyphConstructionSequence(font, &subtable, data, length, num_glyphs,
 504                                           offset_vert_glyph_coverage,
 505                                           vert_glyph_count,
 506                                           sequence_end) ||
 507       !ParseMathGlyphConstructionSequence(font, &subtable, data, length, num_glyphs,
 508                                           offset_horiz_glyph_coverage,
 509                                           horiz_glyph_count,
 510                                           sequence_end)) {
 511     return OTS_FAILURE();
 512   }
 513
 514   return true;
 515 }
 516
 517 }  // namespace
 518
 519 #define DROP_THIS_TABLE(msg_) \
 520   do { \
 521     OTS_FAILURE_MSG(msg_ ", table discarded"); \
 522     font->math->data = 0; \
 523     font->math->length = 0; \
 524   } while (0)
 525
 526 namespace ots {
 527
 528 bool ots_math_parse(Font *font, const uint8_t *data, size_t length) {
 529   // Grab the number of glyphs in the font from the maxp table to check
 530   // GlyphIDs in MATH table.
 531   if (!font->maxp) {
 532     return OTS_FAILURE();
 533   }
 534   const uint16_t num_glyphs = font->maxp->num_glyphs;
 535
 536   Buffer table(data, length);
 537
 538   OpenTypeMATH* math = new OpenTypeMATH;
 539   font->math = math;
 540
 541   uint32_t version = 0;
 542   if (!table.ReadU32(&version)) {
 543     return OTS_FAILURE();
 544   }
 545   if (version != 0x00010000) {
 546     DROP_THIS_TABLE("bad MATH version");
 547     return true;
 548   }
 549
 550   uint16_t offset_math_constants = 0;
 551   uint16_t offset_math_glyph_info = 0;
 552   uint16_t offset_math_variants = 0;
 553   if (!table.ReadU16(&offset_math_constants) ||
 554       !table.ReadU16(&offset_math_glyph_info) ||
 555       !table.ReadU16(&offset_math_variants)) {
 556     return OTS_FAILURE();
 557   }
 558
 559   if (offset_math_constants >= length ||
 560       offset_math_constants < kMathHeaderSize ||
 561       offset_math_glyph_info >= length ||
 562       offset_math_glyph_info < kMathHeaderSize ||
 563       offset_math_variants >= length ||
 564       offset_math_variants < kMathHeaderSize) {
 565     DROP_THIS_TABLE("bad offset in MATH header");
 566     return true;
 567   }
 568
 569   if (!ParseMathConstantsTable(font, data + offset_math_constants,
 570                                length - offset_math_constants)) {
 571     DROP_THIS_TABLE("failed to parse MathConstants table");
 572     return true;
 573   }
 574   if (!ParseMathGlyphInfoTable(font, data + offset_math_glyph_info,
 575                                length - offset_math_glyph_info, num_glyphs)) {
 576     DROP_THIS_TABLE("failed to parse MathGlyphInfo table");
 577     return true;
 578   }
 579   if (!ParseMathVariantsTable(font, data + offset_math_variants,
 580                               length - offset_math_variants, num_glyphs)) {
 581     DROP_THIS_TABLE("failed to parse MathVariants table");
 582     return true;
 583   }
 584
 585   math->data = data;
 586   math->length = length;
 587   return true;
 588 }
 589
 590 bool ots_math_should_serialise(Font *font) {
 591   return font->math != NULL && font->math->data != NULL;
 592 }
 593
 594 bool ots_math_serialise(OTSStream *out, Font *font) {
 595   if (!out->Write(font->math->data, font->math->length)) {
 596     return OTS_FAILURE();
 597   }
 598
 599   return true;
 600 }
 601
 602 void ots_math_reuse(Font *font, Font *other) {
 603   font->math = other->math;
 604   font->math_reused = true;
 605 }
 606
 607 void ots_math_free(Font *font) {
 608   delete font->math;
 609 }
 610
 611 }  // namespace ots
 612
 613 #undef TABLE_NAME
 614 #undef DROP_THIS_TABLE