C++ Twine::toVector方法代码示例

void Value::setName(const Twine &NewName) {
  // Fast path for common IRBuilder case of setName("") when there is no name.
  if (NewName.isTriviallyEmpty() && !hasName())
    return;

  SmallString<256> NameData;
  NewName.toVector(NameData);

  const char *NameStr = NameData.data();
  unsigned NameLen = NameData.size();

  // Name isn't changing?
  if (getName() == StringRef(NameStr, NameLen))
    return;

  assert(getType() != Type::getVoidTy(getContext()) &&
         "Cannot assign a name to void values!");

  // Get the symbol table to update for this object.
  ValueSymbolTable *ST;
  if (getSymTab(this, ST))
    return;  // Cannot set a name on this value (e.g. constant).

  if (!ST) { // No symbol table to update?  Just do the change.
    if (NameLen == 0) {
      // Free the name for this value.
      Name->Destroy();
      Name = 0;
      return;
    }

    if (Name)
      Name->Destroy();

    // NOTE: Could optimize for the case the name is shrinking to not deallocate
    // then reallocated.

    // Create the new name.
    Name = ValueName::Create(NameStr, NameStr+NameLen);
    Name->setValue(this);
    return;
  }

  // NOTE: Could optimize for the case the name is shrinking to not deallocate
  // then reallocated.
  if (hasName()) {
    // Remove old name.
    ST->removeValueName(Name);
    Name->Destroy();
    Name = 0;

    if (NameLen == 0)
      return;
  }

  // Name is changing to something new.
  Name = ST->createValueName(StringRef(NameStr, NameLen), this);
}

void native(const Twine &path, SmallVectorImpl<char> &result, Style style) {
  assert((!path.isSingleStringRef() ||
          path.getSingleStringRef().data() != result.data()) &&
         "path and result are not allowed to overlap!");
  // Clear result.
  result.clear();
  path.toVector(result);
  native(result, style);
}

ErrorOr<Entry *> VFSFromYAML::lookupPath(const Twine &Path_) {
  SmallString<256> Path;
  Path_.toVector(Path);

  // Handle relative paths
  if (error_code EC = sys::fs::make_absolute(Path))
    return EC;

  if (Path.empty())
    return error_code(errc::invalid_argument, system_category());

  sys::path::const_iterator Start = sys::path::begin(Path);
  sys::path::const_iterator End = sys::path::end(Path);
  for (std::vector<Entry *>::iterator I = Roots.begin(), E = Roots.end();
       I != E; ++I) {
    ErrorOr<Entry *> Result = lookupPath(Start, End, *I);
    if (Result || Result.getError() != errc::no_such_file_or_directory)
      return Result;
  }
  return error_code(errc::no_such_file_or_directory, system_category());
}

void MCStreamer::EmitRawText(const Twine &T) {
  SmallString<128> Str;
  T.toVector(Str);
  EmitRawText(Str.str());
}

static std::error_code createUniqueEntity(const Twine &Model, int &ResultFD,
                                          SmallVectorImpl<char> &ResultPath,
                                          bool MakeAbsolute, unsigned Mode,
                                          FSEntity Type) {
  SmallString<128> ModelStorage;
  Model.toVector(ModelStorage);

  if (MakeAbsolute) {
    // Make model absolute by prepending a temp directory if it's not already.
    if (!sys::path::is_absolute(Twine(ModelStorage))) {
      SmallString<128> TDir;
      sys::path::system_temp_directory(true, TDir);
      sys::path::append(TDir, Twine(ModelStorage));
      ModelStorage.swap(TDir);
    }
  }

  // From here on, DO NOT modify model. It may be needed if the randomly chosen
  // path already exists.
  ResultPath = ModelStorage;
  // Null terminate.
  ResultPath.push_back(0);
  ResultPath.pop_back();

retry_random_path:
  // Replace '%' with random chars.
  for (unsigned i = 0, e = ModelStorage.size(); i != e; ++i) {
    if (ModelStorage[i] == '%')
      ResultPath[i] = "0123456789abcdef"[sys::Process::GetRandomNumber() & 15];
  }

  // Try to open + create the file.
  switch (Type) {
  case FS_File: {
    if (std::error_code EC =
            sys::fs::openFileForWrite(Twine(ResultPath.begin()), ResultFD,
                                      sys::fs::F_RW | sys::fs::F_Excl, Mode)) {
      if (EC == errc::file_exists)
        goto retry_random_path;
      return EC;
    }

    return std::error_code();
  }

  case FS_Name: {
    std::error_code EC =
        sys::fs::access(ResultPath.begin(), sys::fs::AccessMode::Exist);
    if (EC == errc::no_such_file_or_directory)
      return std::error_code();
    if (EC)
      return EC;
    goto retry_random_path;
  }

  case FS_Dir: {
    if (std::error_code EC =
            sys::fs::create_directory(ResultPath.begin(), false)) {
      if (EC == errc::file_exists)
        goto retry_random_path;
      return EC;
    }
    return std::error_code();
  }
  }
  llvm_unreachable("Invalid Type");
}

static std::error_code
createUniqueEntity(const Twine &Model, int &ResultFD,
                   SmallVectorImpl<char> &ResultPath, bool MakeAbsolute,
                   unsigned Mode, FSEntity Type,
                   sys::fs::OpenFlags Flags = sys::fs::OF_None) {
  SmallString<128> ModelStorage;
  Model.toVector(ModelStorage);

  if (MakeAbsolute) {
    // Make model absolute by prepending a temp directory if it's not already.
    if (!sys::path::is_absolute(Twine(ModelStorage))) {
      SmallString<128> TDir;
      sys::path::system_temp_directory(true, TDir);
      sys::path::append(TDir, Twine(ModelStorage));
      ModelStorage.swap(TDir);
    }
  }

  // From here on, DO NOT modify model. It may be needed if the randomly chosen
  // path already exists.
  ResultPath = ModelStorage;
  // Null terminate.
  ResultPath.push_back(0);
  ResultPath.pop_back();

  // Limit the number of attempts we make, so that we don't infinite loop. E.g.
  // "permission denied" could be for a specific file (so we retry with a
  // different name) or for the whole directory (retry would always fail).
  // Checking which is racy, so we try a number of times, then give up.
  std::error_code EC;
  for (int Retries = 128; Retries > 0; --Retries) {
    // Replace '%' with random chars.
    for (unsigned i = 0, e = ModelStorage.size(); i != e; ++i) {
      if (ModelStorage[i] == '%')
        ResultPath[i] =
            "0123456789abcdef"[sys::Process::GetRandomNumber() & 15];
    }

    // Try to open + create the file.
    switch (Type) {
    case FS_File: {
      EC = sys::fs::openFileForReadWrite(Twine(ResultPath.begin()), ResultFD,
                                         sys::fs::CD_CreateNew, Flags, Mode);
      if (EC) {
        // errc::permission_denied happens on Windows when we try to open a file
        // that has been marked for deletion.
        if (EC == errc::file_exists || EC == errc::permission_denied)
          continue;
        return EC;
      }

      return std::error_code();
    }

    case FS_Name: {
      EC = sys::fs::access(ResultPath.begin(), sys::fs::AccessMode::Exist);
      if (EC == errc::no_such_file_or_directory)
        return std::error_code();
      if (EC)
        return EC;
      continue;
    }

    case FS_Dir: {
      EC = sys::fs::create_directory(ResultPath.begin(), false);
      if (EC) {
        if (EC == errc::file_exists)
          continue;
        return EC;
      }
      return std::error_code();
    }
    }
    llvm_unreachable("Invalid Type");
  }
  return EC;
}