C++ BitstreamCursor::EnterSubBlock方法代码示例

static bool enterTopLevelModuleBlock(llvm::BitstreamCursor &cursor,
                                     unsigned ID,
                                     bool shouldReadBlockInfo = true) {
  auto next = cursor.advance();

  if (next.Kind != llvm::BitstreamEntry::SubBlock)
    return false;

  if (next.ID == llvm::bitc::BLOCKINFO_BLOCK_ID) {
    if (shouldReadBlockInfo) {
      if (cursor.ReadBlockInfoBlock())
        return false;
    } else {
      if (cursor.SkipBlock())
        return false;
    }
    return enterTopLevelModuleBlock(cursor, ID, false);
  }

  if (next.ID != ID)
    return false;

  cursor.EnterSubBlock(ID);
  return true;
}

LoadResult DiagLoader::readMetaBlock(llvm::BitstreamCursor &Stream) {
  if (Stream.EnterSubBlock(lfort::serialized_diags::BLOCK_META)) {
    reportInvalidFile("Malformed metadata block");
    return Failure;
  }

  bool versionChecked = false;
  
  while (true) {
    unsigned blockOrCode = 0;
    StreamResult Res = readToNextRecordOrBlock(Stream, "Metadata Block",
                                               blockOrCode);
    
    switch(Res) {
      case Read_EndOfStream:
        llvm_unreachable("EndOfStream handled by readToNextRecordOrBlock");
      case Read_Failure:
        return Failure;
      case Read_Record:
        break;
      case Read_BlockBegin:
        if (Stream.SkipBlock()) {
          reportInvalidFile("Malformed metadata block");
          return Failure;
        }
      case Read_BlockEnd:
        if (!versionChecked) {
          reportInvalidFile("Diagnostics file does not contain version"
                            " information");
          return Failure;
        }
        return Success;
    }
    
    RecordData Record;
    const char *Blob;
    unsigned BlobLen;
    unsigned recordID = Stream.ReadRecord(blockOrCode, Record, &Blob, &BlobLen);
    
    if (recordID == serialized_diags::RECORD_VERSION) {
      if (Record.size() < 1) {
        reportInvalidFile("malformed VERSION identifier in diagnostics file");
        return Failure;
      }
      if (Record[0] > MaxSupportedVersion) {
        reportInvalidFile("diagnosics file is a newer version than the one "
                          "supported");
        return Failure;
      }
      versionChecked = true;
    }
  }
}

bool ModuleFile::readCommentBlock(llvm::BitstreamCursor &cursor) {
  cursor.EnterSubBlock(COMMENT_BLOCK_ID);

  SmallVector<uint64_t, 4> scratch;
  StringRef blobData;

  while (true) {
    auto next = cursor.advance();
    switch (next.Kind) {
    case llvm::BitstreamEntry::EndBlock:
      return true;

    case llvm::BitstreamEntry::Error:
      return false;

    case llvm::BitstreamEntry::SubBlock:
      // Unknown sub-block, which this version of the compiler won't use.
      if (cursor.SkipBlock())
        return false;
      break;

    case llvm::BitstreamEntry::Record:
      scratch.clear();
      unsigned kind = cursor.readRecord(next.ID, scratch, &blobData);

      switch (kind) {
      case comment_block::DECL_COMMENTS:
        DeclCommentTable = readDeclCommentTable(scratch, blobData);
        break;
      case comment_block::GROUP_NAMES:
        GroupNamesMap = readGroupTable(scratch, blobData);
        break;
      default:
        // Unknown index kind, which this version of the compiler won't use.
        break;
      }
      break;
    }
  }
}

std::error_code
SerializedDiagnosticReader::readMetaBlock(llvm::BitstreamCursor &Stream) {
  if (Stream.EnterSubBlock(clang::serialized_diags::BLOCK_META))
    return SDError::MalformedMetadataBlock;

  bool VersionChecked = false;

  while (true) {
    unsigned BlockOrCode = 0;
    llvm::ErrorOr<Cursor> Res = skipUntilRecordOrBlock(Stream, BlockOrCode);
    if (!Res)
      Res.getError();

    switch (Res.get()) {
    case Cursor::Record:
      break;
    case Cursor::BlockBegin:
      if (Stream.SkipBlock())
        return SDError::MalformedMetadataBlock;
    case Cursor::BlockEnd:
      if (!VersionChecked)
        return SDError::MissingVersion;
      return std::error_code();
    }

    SmallVector<uint64_t, 1> Record;
    unsigned RecordID = Stream.readRecord(BlockOrCode, Record);

    if (RecordID == RECORD_VERSION) {
      if (Record.size() < 1)
        return SDError::MissingVersion;
      if (Record[0] > VersionNumber)
        return SDError::VersionMismatch;
      VersionChecked = true;
    }
  }
}

bool ModuleFile::readIndexBlock(llvm::BitstreamCursor &cursor) {
  cursor.EnterSubBlock(INDEX_BLOCK_ID);

  SmallVector<uint64_t, 4> scratch;
  StringRef blobData;

  while (true) {
    auto next = cursor.advance();
    switch (next.Kind) {
    case llvm::BitstreamEntry::EndBlock:
      return true;

    case llvm::BitstreamEntry::Error:
      return false;

    case llvm::BitstreamEntry::SubBlock:
      // Unknown sub-block, which this version of the compiler won't use.
      if (cursor.SkipBlock())
        return false;
      break;

    case llvm::BitstreamEntry::Record:
      scratch.clear();
      blobData = {};
      unsigned kind = cursor.readRecord(next.ID, scratch, &blobData);

      switch (kind) {
      case index_block::DECL_OFFSETS:
        assert(blobData.empty());
        Decls.assign(scratch.begin(), scratch.end());
        break;
      case index_block::DECL_CONTEXT_OFFSETS:
        assert(blobData.empty());
        DeclContexts.assign(scratch.begin(), scratch.end());
        break;
      case index_block::TYPE_OFFSETS:
        assert(blobData.empty());
        Types.assign(scratch.begin(), scratch.end());
        break;
      case index_block::IDENTIFIER_OFFSETS:
        assert(blobData.empty());
        Identifiers.assign(scratch.begin(), scratch.end());
        break;
      case index_block::TOP_LEVEL_DECLS:
        TopLevelDecls = readDeclTable(scratch, blobData);
        break;
      case index_block::OPERATORS:
        OperatorDecls = readDeclTable(scratch, blobData);
        break;
      case index_block::EXTENSIONS:
        ExtensionDecls = readDeclTable(scratch, blobData);
        break;
      case index_block::CLASS_MEMBERS:
        ClassMembersByName = readDeclTable(scratch, blobData);
        break;
      case index_block::OPERATOR_METHODS:
        OperatorMethodDecls = readDeclTable(scratch, blobData);
        break;
      case index_block::OBJC_METHODS:
        ObjCMethods = readObjCMethodTable(scratch, blobData);
        break;
      case index_block::ENTRY_POINT:
        assert(blobData.empty());
        setEntryPointClassID(scratch.front());
        break;
      case index_block::LOCAL_TYPE_DECLS:
        LocalTypeDecls = readLocalDeclTable(scratch, blobData);
        break;
      case index_block::LOCAL_DECL_CONTEXT_OFFSETS:
        assert(blobData.empty());
        LocalDeclContexts.assign(scratch.begin(), scratch.end());
        break;
      case index_block::NORMAL_CONFORMANCE_OFFSETS:
        assert(blobData.empty());
        NormalConformances.assign(scratch.begin(), scratch.end());
        break;

      default:
        // Unknown index kind, which this version of the compiler won't use.
        break;
      }
      break;
    }
  }
}

static ValidationInfo
validateControlBlock(llvm::BitstreamCursor &cursor,
                     SmallVectorImpl<uint64_t> &scratch,
                     ExtendedValidationInfo *extendedInfo) {
  // The control block is malformed until we've at least read a major version
  // number.
  ValidationInfo result;
  bool versionSeen = false;

  auto next = cursor.advance();
  while (next.Kind != llvm::BitstreamEntry::EndBlock) {
    if (next.Kind == llvm::BitstreamEntry::Error) {
      result.status = Status::Malformed;
      return result;
    }

    if (next.Kind == llvm::BitstreamEntry::SubBlock) {
      if (next.ID == OPTIONS_BLOCK_ID && extendedInfo) {
        cursor.EnterSubBlock(OPTIONS_BLOCK_ID);
        if (!readOptionsBlock(cursor, scratch, *extendedInfo)) {
          result.status = Status::Malformed;
          return result;
        }
      } else {
        // Unknown metadata sub-block, possibly for use by a future version of
        // the module format.
        if (cursor.SkipBlock()) {
          result.status = Status::Malformed;
          return result;
        }
      }
      next = cursor.advance();
      continue;
    }

    scratch.clear();
    StringRef blobData;
    unsigned kind = cursor.readRecord(next.ID, scratch, &blobData);
    switch (kind) {
    case control_block::METADATA: {
      if (versionSeen) {
        result.status = Status::Malformed;
        break;
      }

      uint16_t versionMajor = scratch[0];
      if (versionMajor > VERSION_MAJOR)
        result.status = Status::FormatTooNew;
      else if (versionMajor < VERSION_MAJOR)
        result.status = Status::FormatTooOld;
      else
        result.status = Status::Valid;

      // Major version 0 does not have stable minor versions.
      if (versionMajor == 0) {
        uint16_t versionMinor = scratch[1];
        if (versionMinor != VERSION_MINOR) {
          if (versionMinor < VERSION_MINOR)
            result.status = Status::FormatTooOld;
          else
            result.status = Status::FormatTooNew;
        }
      }

      versionSeen = true;
      break;
    }
    case control_block::MODULE_NAME:
      result.name = blobData;
      break;
    case control_block::TARGET:
      result.targetTriple = blobData;
      break;
    default:
      // Unknown metadata record, possibly for use by a future version of the
      // module format.
      break;
    }

    next = cursor.advance();
  }

  return result;
}

GlobalModuleIndex::GlobalModuleIndex(std::unique_ptr<llvm::MemoryBuffer> Buffer,
                                     llvm::BitstreamCursor Cursor)
    : Buffer(std::move(Buffer)), IdentifierIndex(), NumIdentifierLookups(),
      NumIdentifierLookupHits() {
  // Read the global index.
  bool InGlobalIndexBlock = false;
  bool Done = false;
  while (!Done) {
    llvm::BitstreamEntry Entry = Cursor.advance();

    switch (Entry.Kind) {
    case llvm::BitstreamEntry::Error:
      return;

    case llvm::BitstreamEntry::EndBlock:
      if (InGlobalIndexBlock) {
        InGlobalIndexBlock = false;
        Done = true;
        continue;
      }
      return;


    case llvm::BitstreamEntry::Record:
      // Entries in the global index block are handled below.
      if (InGlobalIndexBlock)
        break;

      return;

    case llvm::BitstreamEntry::SubBlock:
      if (!InGlobalIndexBlock && Entry.ID == GLOBAL_INDEX_BLOCK_ID) {
        if (Cursor.EnterSubBlock(GLOBAL_INDEX_BLOCK_ID))
          return;

        InGlobalIndexBlock = true;
      } else if (Cursor.SkipBlock()) {
        return;
      }
      continue;
    }

    SmallVector<uint64_t, 64> Record;
    StringRef Blob;
    switch ((IndexRecordTypes)Cursor.readRecord(Entry.ID, Record, &Blob)) {
    case INDEX_METADATA:
      // Make sure that the version matches.
      if (Record.size() < 1 || Record[0] != CurrentVersion)
        return;
      break;

    case MODULE: {
      unsigned Idx = 0;
      unsigned ID = Record[Idx++];

      // Make room for this module's information.
      if (ID == Modules.size())
        Modules.push_back(ModuleInfo());
      else
        Modules.resize(ID + 1);

      // Size/modification time for this module file at the time the
      // global index was built.
      Modules[ID].Size = Record[Idx++];
      Modules[ID].ModTime = Record[Idx++];

      // File name.
      unsigned NameLen = Record[Idx++];
      Modules[ID].FileName.assign(Record.begin() + Idx,
                                  Record.begin() + Idx + NameLen);
      Idx += NameLen;

      // Dependencies
      unsigned NumDeps = Record[Idx++];
      Modules[ID].Dependencies.insert(Modules[ID].Dependencies.end(),
                                      Record.begin() + Idx,
                                      Record.begin() + Idx + NumDeps);
      Idx += NumDeps;

      // Make sure we're at the end of the record.
      assert(Idx == Record.size() && "More module info?");

      // Record this module as an unresolved module.
      // FIXME: this doesn't work correctly for module names containing path
      // separators.
      StringRef ModuleName = llvm::sys::path::stem(Modules[ID].FileName);
      // Remove the -<hash of ModuleMapPath>
      ModuleName = ModuleName.rsplit('-').first;
      UnresolvedModules[ModuleName] = ID;
      break;
    }

    case IDENTIFIER_INDEX:
      // Wire up the identifier index.
      if (Record[0]) {
        IdentifierIndex = IdentifierIndexTable::Create(
            (const unsigned char *)Blob.data() + Record[0],
            (const unsigned char *)Blob.data() + sizeof(uint32_t),
            (const unsigned char *)Blob.data(), IdentifierIndexReaderTrait());
      }
//.........这里部分代码省略.........

GlobalModuleIndex::GlobalModuleIndex(FileManager &FileMgr,
                                     llvm::MemoryBuffer *Buffer,
                                     llvm::BitstreamCursor Cursor)
  : Buffer(Buffer), IdentifierIndex(),
    NumIdentifierLookups(), NumIdentifierLookupHits()
{
  typedef llvm::DenseMap<unsigned, LoadedModuleInfo> LoadedModulesMap;
  LoadedModulesMap LoadedModules;
  
  // Read the global index.
  unsigned LargestID = 0;
  bool InGlobalIndexBlock = false;
  bool Done = false;
  bool AnyOutOfDate = false;
  while (!Done) {
    llvm::BitstreamEntry Entry = Cursor.advance();

    switch (Entry.Kind) {
    case llvm::BitstreamEntry::Error:
      return;

    case llvm::BitstreamEntry::EndBlock:
      if (InGlobalIndexBlock) {
        InGlobalIndexBlock = false;
        Done = true;
        continue;
      }
      return;


    case llvm::BitstreamEntry::Record:
      // Entries in the global index block are handled below.
      if (InGlobalIndexBlock)
        break;

      return;

    case llvm::BitstreamEntry::SubBlock:
      if (!InGlobalIndexBlock && Entry.ID == GLOBAL_INDEX_BLOCK_ID) {
        if (Cursor.EnterSubBlock(GLOBAL_INDEX_BLOCK_ID))
          return;

        InGlobalIndexBlock = true;
      } else if (Cursor.SkipBlock()) {
        return;
      }
      continue;
    }

    SmallVector<uint64_t, 64> Record;
    StringRef Blob;
    switch ((IndexRecordTypes)Cursor.readRecord(Entry.ID, Record, &Blob)) {
    case INDEX_METADATA:
      // Make sure that the version matches.
      if (Record.size() < 1 || Record[0] != CurrentVersion)
        return;
      break;

    case MODULE: {
      unsigned Idx = 0;
      unsigned ID = Record[Idx++];
      if (ID > LargestID)
        LargestID = ID;
      
      off_t Size = Record[Idx++];
      time_t ModTime = Record[Idx++];

      // File name.
      unsigned NameLen = Record[Idx++];
      llvm::SmallString<64> FileName(Record.begin() + Idx,
                                     Record.begin() + Idx + NameLen);
      Idx += NameLen;

      // Dependencies
      unsigned NumDeps = Record[Idx++];
      llvm::SmallVector<unsigned, 2>
        Dependencies(Record.begin() + Idx, Record.begin() + Idx + NumDeps);

      // Find the file. If we can't find it, ignore it.
      const FileEntry *File = FileMgr.getFile(FileName);
      if (!File) {
        AnyOutOfDate = true;
        break;
      }

      // If the module file is newer than the index, ignore it.
      if (File->getSize() != Size || File->getModificationTime() != ModTime) {
        AnyOutOfDate = true;
        break;
      }

      // Record this module. The dependencies will be resolved later.
      LoadedModuleInfo &Info = LoadedModules[ID];
      Info.File = File;
      Info.Dependencies.swap(Dependencies);
      break;
    }

    case IDENTIFIER_INDEX:
      // Wire up the identifier index.
//.........这里部分代码省略.........