C++ EBMLDataSize类代码示例

void MatroskaFileParser::lookForNextBlock() {
#ifdef DEBUG
  fprintf(stderr, "looking for Block\n");
#endif
  // Read and skip over each Matroska header, until we get to a 'Cluster':
  EBMLId id;
  EBMLDataSize size;
  while (fCurrentParseState == LOOKING_FOR_BLOCK) {
    while (!parseEBMLIdAndSize(id, size)) {}
#ifdef DEBUG
    fprintf(stderr, "MatroskaFileParser::lookForNextBlock(): Parsed id 0x%s (%s), size: %lld\n", id.hexString(), id.stringName(), size.val());
#endif
    switch (id.val()) {
      case MATROSKA_ID_SEGMENT: { // 'Segment' header: enter this
	break;
      }
      case MATROSKA_ID_CLUSTER: { // 'Cluster' header: enter this
	break;
      }
      case MATROSKA_ID_TIMECODE: { // 'Timecode' header: get this value
	unsigned timecode;
	if (parseEBMLVal_unsigned(size, timecode)) {
	  fClusterTimecode = timecode;
#ifdef DEBUG
	  fprintf(stderr, "\tCluster timecode: %d (== %f seconds)\n", fClusterTimecode, fClusterTimecode*(fOurFile.fTimecodeScale/1000000000.0));
#endif
	}
	break;
      }
      case MATROSKA_ID_BLOCK_GROUP: { // 'Block Group' header: enter this
	break;
      }
      case MATROSKA_ID_SIMPLEBLOCK:
      case MATROSKA_ID_BLOCK: { // 'SimpleBlock' or 'Block' header: enter this (and we're done)
	fBlockSize = (unsigned)size.val();
	fCurrentParseState = PARSING_BLOCK;
	break;
      }
      case MATROSKA_ID_BLOCK_DURATION: { // 'Block Duration' header: get this value (but we currently don't do anything with it)
	unsigned blockDuration;
	if (parseEBMLVal_unsigned(size, blockDuration)) {
#ifdef DEBUG
	  fprintf(stderr, "\tblock duration: %d (== %f ms)\n", blockDuration, (float)(blockDuration*fOurFile.fTimecodeScale/1000000.0));
#endif
	}
	break;
      }
      default: { // skip over this header
	skipHeader(size);
#ifdef DEBUG
	fprintf(stderr, "\tskipped %lld bytes\n", size.val());
#endif
	break;
      }
    }
    setParseState();
  }
}

Boolean MatroskaFileParser::parseEBMLVal_unsigned(EBMLDataSize& size, unsigned& result) {
  if (size.val() > 4) return False; // size too large

  u_int64_t result64;
  if (!parseEBMLVal_unsigned64(size, result64)) return False;

  result = (unsigned)result64;

  return True;
}

void MatroskaFileParser::skipHeader(EBMLDataSize const& size) {
  unsigned sv = (unsigned)size.val();

  // Hack: To avoid tripping into a parser 'internal error' if we try to skip an excessively large distance.
  // (Such large distances are likely caused by erroneous data.  We might not be able to recover from this, but at least we won't
  //  generate a parser 'internal error'.)
  if (sv > bankSize()-12) sv = bankSize()-12;
  
  skipBytes(sv);
  fCurOffsetInFile += sv;
}

Boolean MatroskaFileParser::parseEBMLVal_unsigned64(EBMLDataSize& size, u_int64_t& result) {
  u_int64_t sv = size.val();
  if (sv > 8) return False; // size too large

  result = 0; // initially
  for (unsigned i = (unsigned)sv; i > 0; --i) {
    if (fLimitOffsetInFile > 0 && fCurOffsetInFile > fLimitOffsetInFile) return False; // We've hit our pre-set limit

    u_int8_t c = get1Byte();
    ++fCurOffsetInFile;

    result = result*256 + c;
  }

  return True;
}

Boolean MatroskaFileParser::parseEBMLVal_float(EBMLDataSize& size, float& result) {
  switch (size.val()) {
    case 4: {
      unsigned resultAsUnsigned;

      if (!parseEBMLVal_unsigned(size, resultAsUnsigned)) return False;
      result = *(float*)&resultAsUnsigned;
      return True;
    }
    case 8: {
      u_int64_t resultAsU64;

      if (!parseEBMLVal_unsigned64(size, resultAsU64)) return False;
      result = (float)*(double*)&resultAsU64;
      return True;
    }
    default: {
      return False;
    }
  }
}

Boolean MatroskaFileParser::parseEBMLVal_binary(EBMLDataSize& size, u_int8_t*& result) {
  unsigned resultLength = (unsigned)size.val();
  result = new u_int8_t[resultLength];
  if (result == NULL) return False;

  u_int8_t* p = result;
  unsigned i;
  for (i = 0; i < resultLength; ++i) {
    if (fLimitOffsetInFile > 0 && fCurOffsetInFile > fLimitOffsetInFile) break; // We've hit our pre-set limit

    u_int8_t c = get1Byte();
    ++fCurOffsetInFile;

    *p++ = c;
  }
  if (i < resultLength) { // an error occurred
    delete[] result;
    result = NULL;
    return False;
  }

  return True;
}

Boolean MatroskaFileParser::parseEBMLVal_string(EBMLDataSize& size, char*& result) {
  unsigned resultLength = (unsigned)size.val();
  result = new char[resultLength + 1]; // allow for the trailing '\0'
  if (result == NULL) return False;

  char* p = result;
  unsigned i;
  for (i = 0; i < resultLength; ++i) {
    if (fLimitOffsetInFile > 0 && fCurOffsetInFile > fLimitOffsetInFile) break; // We've hit our pre-set limit

    u_int8_t c = get1Byte();
    ++fCurOffsetInFile;

    *p++ = c;
  }
  if (i < resultLength) { // an error occurred
    delete[] result;
    result = NULL;
    return False;
  }
  *p = '\0';

  return True;
}

Boolean MatroskaFileParser::parseCues() {
#if defined(DEBUG) || defined(DEBUG_CUES)
  fprintf(stderr, "parsing Cues\n");
#endif
  EBMLId id;
  EBMLDataSize size;

  // Read the next header, which should be MATROSKA_ID_CUES:
  if (!parseEBMLIdAndSize(id, size) || id != MATROSKA_ID_CUES) return True; // The header wasn't what we expected, so we're done
  fLimitOffsetInFile = fCurOffsetInFile + size.val(); // Make sure we don't read past the end of this header

  double currentCueTime = 0.0;
  u_int64_t currentClusterOffsetInFile = 0;

  while (fCurOffsetInFile < fLimitOffsetInFile) {
    while (!parseEBMLIdAndSize(id, size)) {}
#ifdef DEBUG_CUES
    if (id == MATROSKA_ID_CUE_POINT) fprintf(stderr, "\n"); // makes debugging output easier to read
    fprintf(stderr, "MatroskaFileParser::parseCues(): Parsed id 0x%s (%s), size: %lld\n", id.hexString(), id.stringName(), size.val());
#endif
    switch (id.val()) {
      case MATROSKA_ID_CUE_POINT: { // 'Cue Point' header: enter this
	break;
      }
      case MATROSKA_ID_CUE_TIME: { // 'Cue Time' header: get this value
	unsigned cueTime;
	if (parseEBMLVal_unsigned(size, cueTime)) {
	  currentCueTime = cueTime*(fOurFile.fTimecodeScale/1000000000.0);
#ifdef DEBUG_CUES
	  fprintf(stderr, "\tCue Time %d (== %f seconds)\n", cueTime, currentCueTime);
#endif
	}
	break;
      }
      case MATROSKA_ID_CUE_TRACK_POSITIONS: { // 'Cue Track Positions' header: enter this
	break;
      }
      case MATROSKA_ID_CUE_TRACK: { // 'Cue Track' header: get this value (but only for debugging; we don't do anything with it)
	unsigned cueTrack;
	if (parseEBMLVal_unsigned(size, cueTrack)) {
#ifdef DEBUG_CUES
	  fprintf(stderr, "\tCue Track %d\n", cueTrack);
#endif
	}
	break;
      }
      case MATROSKA_ID_CUE_CLUSTER_POSITION: { // 'Cue Cluster Position' header: get this value
	u_int64_t cueClusterPosition;
	if (parseEBMLVal_unsigned64(size, cueClusterPosition)) {
	  currentClusterOffsetInFile = fOurFile.fSegmentDataOffset + cueClusterPosition;
#ifdef DEBUG_CUES
	  fprintf(stderr, "\tCue Cluster Position %llu (=> offset within the file: %llu (0x%llx))\n", cueClusterPosition, currentClusterOffsetInFile, currentClusterOffsetInFile);
#endif
	  // Record this cue point:
	  fOurFile.addCuePoint(currentCueTime, currentClusterOffsetInFile, 1/*default block number within cluster*/);
	}
	break;
      }
      case MATROSKA_ID_CUE_BLOCK_NUMBER: { // 'Cue Block Number' header: get this value
	unsigned cueBlockNumber;
	if (parseEBMLVal_unsigned(size, cueBlockNumber) && cueBlockNumber != 0) {
#ifdef DEBUG_CUES
	  fprintf(stderr, "\tCue Block Number %d\n", cueBlockNumber);
#endif
	  // Record this cue point (overwriting any existing entry for this cue time):
	  fOurFile.addCuePoint(currentCueTime, currentClusterOffsetInFile, cueBlockNumber);
	}
	break;
      }
      default: { // We don't process this header, so just skip over it:
	skipHeader(size);
#ifdef DEBUG_CUES
	fprintf(stderr, "\tskipped %lld bytes\n", size.val());
#endif
	break;
      }
    }
    setParseState();
  }

  fLimitOffsetInFile = 0; // reset
#if defined(DEBUG) || defined(DEBUG_CUES)
  fprintf(stderr, "done parsing Cues\n");
#endif
#ifdef DEBUG_CUES
  fprintf(stderr, "Cue Point tree: ");
  fOurFile.printCuePoints(stderr);
  fprintf(stderr, "\n");
#endif
  return True; // we're done parsing Cues
}