text: /*
   * Copyright 2014 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #ifndef FLATBUFFERS_H_
  #define FLATBUFFERS_H_
  
  #include "flatbuffers/base.h"
  
  namespace flatbuffers {
  // Wrapper for uoffset_t to allow safe template specialization.
  // Value is allowed to be 0 to indicate a null object (see e.g. AddOffset).
  template<typename T> struct Offset {
    uoffset_t o;
    Offset() : o(0) {}
    Offset(uoffset_t _o) : o(_o) {}
    Offset<void> Union() const { return Offset<void>(o); }
    bool IsNull() const { return !o; }
  };
  
  inline void EndianCheck() {
    int endiantest = 1;
    // If this fails, see FLATBUFFERS_LITTLEENDIAN above.
    assert(*reinterpret_cast<char *>(&endiantest) == FLATBUFFERS_LITTLEENDIAN);
    (void)endiantest;
  }
  
  template<typename T> FLATBUFFERS_CONSTEXPR size_t AlignOf() {
    // clang-format off
    #ifdef _MSC_VER
      return __alignof(T);
    #else
      #ifndef alignof
        return __alignof__(T);
      #else
        return alignof(T);
      #endif
    #endif
    // clang-format on
  }
  
  // When we read serialized data from memory, in the case of most scalars,
  // we want to just read T, but in the case of Offset, we want to actually
  // perform the indirection and return a pointer.
  // The template specialization below does just that.
  // It is wrapped in a struct since function templates can't overload on the
  // return type like this.
  // The typedef is for the convenience of callers of this function
  // (avoiding the need for a trailing return decltype)
  template<typename T> struct IndirectHelper {
    typedef T return_type;
    typedef T mutable_return_type;
    static const size_t element_stride = sizeof(T);
    static return_type Read(const uint8_t *p, uoffset_t i) {
      return EndianScalar((reinterpret_cast<const T *>(p))[i]);
    }
  };
  template<typename T> struct IndirectHelper<Offset<T>> {
    typedef const T *return_type;
    typedef T *mutable_return_type;
    static const size_t element_stride = sizeof(uoffset_t);
    static return_type Read(const uint8_t *p, uoffset_t i) {
      p += i * sizeof(uoffset_t);
      return reinterpret_cast<return_type>(p + ReadScalar<uoffset_t>(p));
    }
  };
  template<typename T> struct IndirectHelper<const T *> {
    typedef const T *return_type;
    typedef T *mutable_return_type;
    static const size_t element_stride = sizeof(T);
    static return_type Read(const uint8_t *p, uoffset_t i) {
      return reinterpret_cast<const T *>(p + i * sizeof(T));
    }
  };
  
  // An STL compatible iterator implementation for Vector below, effectively
  // calling Get() for every element.
  template<typename T, typename IT> struct VectorIterator {
    typedef std::random_access_iterator_tag iterator_category;
    typedef IT value_type;
    typedef uoffset_t difference_type;
    typedef IT *pointer;
    typedef IT &reference;
  
    VectorIterator(const uint8_t *data, uoffset_t i)
        : data_(data + IndirectHelper<T>::element_stride * i) {}
    VectorIterator(const VectorIterator &other) : data_(other.data_) {}
  
    VectorIterator &operator=(const VectorIterator &other) {
      data_ = other.data_;
      return *this;
    }
  
    VectorIterator &operator=(VectorIterator &&other) {
      data_ = other.data_;
      return *this;
    }
  
    bool operator==(const VectorIterator &other) const {
      return data_ == other.data_;
    }
  
    bool operator<(const VectorIterator &other) const {
      return data_ < other.data_;
    }
  
    bool operator!=(const VectorIterator &other) const {
      return data_ != other.data_;
    }
  
    ptrdiff_t operator-(const VectorIterator &other) const {
      return (data_ - other.data_) / IndirectHelper<T>::element_stride;
    }
  
    IT operator*() const { return IndirectHelper<T>::Read(data_, 0); }
  
    IT operator->() const { return IndirectHelper<T>::Read(data_, 0); }
  
    VectorIterator &operator++() {
      data_ += IndirectHelper<T>::element_stride;
      return *this;
    }
  
    VectorIterator operator++(int) {
      VectorIterator temp(data_, 0);
      data_ += IndirectHelper<T>::element_stride;
      return temp;
    }
  
    VectorIterator operator+(const uoffset_t &offset) const {
      return VectorIterator(data_ + offset * IndirectHelper<T>::element_stride,
                            0);
    }
  
    VectorIterator &operator+=(const uoffset_t &offset) {
      data_ += offset * IndirectHelper<T>::element_stride;
      return *this;
    }
  
    VectorIterator &operator--() {
      data_ -= IndirectHelper<T>::element_stride;
      return *this;
    }
  
    VectorIterator operator--(int) {
      VectorIterator temp(data_, 0);
      data_ -= IndirectHelper<T>::element_stride;
      return temp;
    }
  
    VectorIterator operator-(const uoffset_t &offset) {
      return VectorIterator(data_ - offset * IndirectHelper<T>::element_stride,
                            0);
    }
  
    VectorIterator &operator-=(const uoffset_t &offset) {
      data_ -= offset * IndirectHelper<T>::element_stride;
      return *this;
    }
  
   private:
    const uint8_t *data_;
  };
  
  struct String;
  
  // This is used as a helper type for accessing vectors.
  // Vector::data() assumes the vector elements start after the length field.
  template<typename T> class Vector {
   public:
    typedef VectorIterator<T, typename IndirectHelper<T>::mutable_return_type>
        iterator;
    typedef VectorIterator<T, typename IndirectHelper<T>::return_type>
        const_iterator;
  
    uoffset_t size() const { return EndianScalar(length_); }
  
    // Deprecated: use size(). Here for backwards compatibility.
    uoffset_t Length() const { return size(); }
  
    typedef typename IndirectHelper<T>::return_type return_type;
    typedef typename IndirectHelper<T>::mutable_return_type mutable_return_type;
  
    return_type Get(uoffset_t i) const {
      assert(i < size());
      return IndirectHelper<T>::Read(Data(), i);
    }
  
    return_type operator[](uoffset_t i) const { return Get(i); }
  
    // If this is a Vector of enums, T will be its storage type, not the enum
    // type. This function makes it convenient to retrieve value with enum
    // type E.
    template<typename E> E GetEnum(uoffset_t i) const {
      return static_cast<E>(Get(i));
    }
  
    // If this a vector of unions, this does the cast for you. There's no check
    // to make sure this is the right type!
    template<typename U> const U *GetAs(uoffset_t i) const {
      return reinterpret_cast<const U *>(Get(i));
    }
  
    // If this a vector of unions, this does the cast for you. There's no check
    // to make sure this is actually a string!
    const String *GetAsString(uoffset_t i) const {
      return reinterpret_cast<const String *>(Get(i));
    }
  
    const void *GetStructFromOffset(size_t o) const {
      return reinterpret_cast<const void *>(Data() + o);
    }
  
    iterator begin() { return iterator(Data(), 0); }
    const_iterator begin() const { return const_iterator(Data(), 0); }
  
    iterator end() { return iterator(Data(), size()); }
    const_iterator end() const { return const_iterator(Data(), size()); }
  
    // Change elements if you have a non-const pointer to this object.
    // Scalars only. See reflection.h, and the documentation.
    void Mutate(uoffset_t i, const T &val) {
      assert(i < size());
      WriteScalar(data() + i, val);
    }
  
    // Change an element of a vector of tables (or strings).
    // "val" points to the new table/string, as you can obtain from
    // e.g. reflection::AddFlatBuffer().
    void MutateOffset(uoffset_t i, const uint8_t *val) {
      assert(i < size());
      assert(sizeof(T) == sizeof(uoffset_t));
      WriteScalar(data() + i,
                  static_cast<uoffset_t>(val - (Data() + i * sizeof(uoffset_t))));
    }
  
    // Get a mutable pointer to tables/strings inside this vector.
    mutable_return_type GetMutableObject(uoffset_t i) const {
      assert(i < size());
      return const_cast<mutable_return_type>(IndirectHelper<T>::Read(Data(), i));
    }
  
    // The raw data in little endian format. Use with care.
    const uint8_t *Data() const {
      return reinterpret_cast<const uint8_t *>(&length_ + 1);
    }
  
    uint8_t *Data() { return reinterpret_cast<uint8_t *>(&length_ + 1); }
  
    // Similarly, but typed, much like std::vector::data
    const T *data() const { return reinterpret_cast<const T *>(Data()); }
    T *data() { return reinterpret_cast<T *>(Data()); }
  
    template<typename K> return_type LookupByKey(K key) const {
      void *search_result = std::bsearch(
          &key, Data(), size(), IndirectHelper<T>::element_stride, KeyCompare<K>);
  
      if (!search_result) {
        return nullptr;  // Key not found.
      }
  
      const uint8_t *element = reinterpret_cast<const uint8_t *>(search_result);
  
      return IndirectHelper<T>::Read(element, 0);
    }
  
   protected:
    // This class is only used to access pre-existing data. Don't ever
    // try to construct these manually.
    Vector();
  
    uoffset_t length_;
  
   private:
    // This class is a pointer. Copying will therefore create an invalid object.
    // Private and unimplemented copy constructor.
    Vector(const Vector &);
  
    template<typename K> static int KeyCompare(const void *ap, const void *bp) {
      const K *key = reinterpret_cast<const K *>(ap);
      const uint8_t *data = reinterpret_cast<const uint8_t *>(bp);
      auto table = IndirectHelper<T>::Read(data, 0);
  
      // std::bsearch compares with the operands transposed, so we negate the
      // result here.
      return -table->KeyCompareWithValue(*key);
    }
  };
  
  // Represent a vector much like the template above, but in this case we
  // don't know what the element types are (used with reflection.h).
  class VectorOfAny {
   public:
    uoffset_t size() const { return EndianScalar(length_); }
  
    const uint8_t *Data() const {
      return reinterpret_cast<const uint8_t *>(&length_ + 1);
    }
    uint8_t *Data() { return reinterpret_cast<uint8_t *>(&length_ + 1); }
  
   protected:
    VectorOfAny();
  
    uoffset_t length_;
  
   private:
    VectorOfAny(const VectorOfAny &);
  };
  
  #ifndef FLATBUFFERS_CPP98_STL
  template<typename T, typename U>
  Vector<Offset<T>> *VectorCast(Vector<Offset<U>> *ptr) {
    static_assert(std::is_base_of<T, U>::value, "Unrelated types");
    return reinterpret_cast<Vector<Offset<T>> *>(ptr);
  }
  
  template<typename T, typename U>
  const Vector<Offset<T>> *VectorCast(const Vector<Offset<U>> *ptr) {
    static_assert(std::is_base_of<T, U>::value, "Unrelated types");
    return reinterpret_cast<const Vector<Offset<T>> *>(ptr);
  }
  #endif
  
  // Convenient helper function to get the length of any vector, regardless
  // of wether it is null or not (the field is not set).
  template<typename T> static inline size_t VectorLength(const Vector<T> *v) {
    return v ? v->Length() : 0;
  }
  
  struct String : public Vector<char> {
    const char *c_str() const { return reinterpret_cast<const char *>(Data()); }
    std::string str() const { return std::string(c_str(), Length()); }
  
    bool operator<(const String &o) const {
      return strcmp(c_str(), o.c_str()) < 0;
    }
  };
  
  // Allocator interface. This is flatbuffers-specific and meant only for
  // `vector_downward` usage.
  class Allocator {
   public:
    virtual ~Allocator() {}
  
    // Allocate `size` bytes of memory.
    virtual uint8_t *allocate(size_t size) = 0;
  
    // Deallocate `size` bytes of memory at `p` allocated by this allocator.
    virtual void deallocate(uint8_t *p, size_t size) = 0;
  
    // Reallocate `new_size` bytes of memory, replacing the old region of size
    // `old_size` at `p`. In contrast to a normal realloc, this grows downwards,
    // and is intended specifcally for `vector_downward` use.
    virtual uint8_t *reallocate_downward(uint8_t *old_p, size_t old_size,
                                         size_t new_size) {
      assert(new_size > old_size);  // vector_downward only grows
      uint8_t *new_p = allocate(new_size);
      memcpy(new_p + (new_size - old_size), old_p, old_size);
      deallocate(old_p, old_size);
      return new_p;
    }
  };
  
  // DefaultAllocator uses new/delete to allocate memory regions
  class DefaultAllocator : public Allocator {
   public:
    virtual uint8_t *allocate(size_t size) FLATBUFFERS_OVERRIDE {
      return new uint8_t[size];
    }
  
    virtual void deallocate(uint8_t *p, size_t) FLATBUFFERS_OVERRIDE {
      delete[] p;
    }
  
    static DefaultAllocator &instance() {
      static DefaultAllocator inst;
      return inst;
    }
  };
  
  // DetachedBuffer is a finished flatbuffer memory region, detached from its
  // builder. The original memory region and allocator are also stored so that
  // the DetachedBuffer can manage the memory lifetime.
  class DetachedBuffer {
   public:
    DetachedBuffer()
        : allocator_(nullptr),
          own_allocator_(false),
          buf_(nullptr),
          reserved_(0),
          cur_(nullptr),
          size_(0) {}
  
    DetachedBuffer(Allocator *allocator, bool own_allocator, uint8_t *buf,
                   size_t reserved, uint8_t *cur, size_t sz)
        : allocator_(allocator),
          own_allocator_(own_allocator),
          buf_(buf),
          reserved_(reserved),
          cur_(cur),
          size_(sz) {
      assert(allocator_);
    }
  
    DetachedBuffer(DetachedBuffer &&other)
        : allocator_(other.allocator_),
          own_allocator_(other.own_allocator_),
          buf_(other.buf_),
          reserved_(other.reserved_),
          cur_(other.cur_),
          size_(other.size_) {
      other.reset();
    }
  
    DetachedBuffer &operator=(DetachedBuffer &&other) {
      destroy();
  
      allocator_ = other.allocator_;
      own_allocator_ = other.own_allocator_;
      buf_ = other.buf_;
      reserved_ = other.reserved_;
      cur_ = other.cur_;
      size_ = other.size_;
  
      other.reset();
  
      return *this;
    }
  
    ~DetachedBuffer() { destroy(); }
  
    const uint8_t *data() const { return cur_; }
  
    uint8_t *data() { return cur_; }
  
    size_t size() const { return size_; }
  
    // clang-format off
    #if 0  // disabled for now due to the ordering of classes in this header
    template <class T>
    bool Verify() const {
      Verifier verifier(data(), size());
      return verifier.Verify<T>(nullptr);
    }
  
    template <class T>
    const T* GetRoot() const {
      return flatbuffers::GetRoot<T>(data());
    }
  
    template <class T>
    T* GetRoot() {
      return flatbuffers::GetRoot<T>(data());
    }
    #endif
    // clang-format on
  
    // These may change access mode, leave these at end of public section
    FLATBUFFERS_DELETE_FUNC(DetachedBuffer(const DetachedBuffer &other))
    FLATBUFFERS_DELETE_FUNC(
        DetachedBuffer &operator=(const DetachedBuffer &other))
  
   protected:
    Allocator *allocator_;
    bool own_allocator_;
    uint8_t *buf_;
    size_t reserved_;
    uint8_t *cur_;
    size_t size_;
  
    inline void destroy() {
      if (buf_) {
        assert(allocator_);
        allocator_->deallocate(buf_, reserved_);
      }
      if (own_allocator_ && allocator_) { delete allocator_; }
  
      reset();
    }
  
    inline void reset() {
      allocator_ = nullptr;
      own_allocator_ = false;
      buf_ = nullptr;
      reserved_ = 0;
      cur_ = nullptr;
      size_ = 0;
    }
  };
  
  // This is a minimal replication of std::vector<uint8_t> functionality,
  // except growing from higher to lower addresses. i.e push_back() inserts data
  // in the lowest address in the vector.
  class vector_downward {
   public:
    explicit vector_downward(size_t initial_size = 1024,
                             Allocator *allocator = nullptr,
                             bool own_allocator = false)
        : allocator_(allocator ? allocator : &DefaultAllocator::instance()),
          own_allocator_(own_allocator),
          initial_size_(initial_size),
          reserved_(0),
          buf_(nullptr),
          cur_(nullptr) {
      assert(allocator_);
    }
  
    ~vector_downward() {
      if (buf_) {
        assert(allocator_);
        allocator_->deallocate(buf_, reserved_);
      }
      if (own_allocator_ && allocator_) { delete allocator_; }
    }
  
    void reset() {
      if (buf_) {
        assert(allocator_);
        allocator_->deallocate(buf_, reserved_);
      }
      reserved_ = 0;
      buf_ = nullptr;
      cur_ = nullptr;
    }
  
    void clear() {
      if (buf_) {
        cur_ = buf_ + reserved_;
      } else {
        reserved_ = 0;
        buf_ = nullptr;
        cur_ = nullptr;
      }
    }
  
    // Relinquish the pointer to the caller.
    DetachedBuffer release() {
      DetachedBuffer fb(allocator_, own_allocator_, buf_, reserved_, cur_,
                        size());
      allocator_ = nullptr;
      own_allocator_ = false;
      reserved_ = 0;
      buf_ = nullptr;
      cur_ = nullptr;
      return fb;
    }
  
    size_t growth_policy(size_t bytes) {
      return (bytes == 0) ? initial_size_
                          : ((bytes / 2) & ~(AlignOf<largest_scalar_t>() - 1));
    }
  
    uint8_t *make_space(size_t len) {
      assert(cur_ >= buf_);
      if (len > static_cast<size_t>(cur_ - buf_)) { reallocate(len); }
      cur_ -= len;
      // Beyond this, signed offsets may not have enough range:
      // (FlatBuffers > 2GB not supported).
      assert(size() < FLATBUFFERS_MAX_BUFFER_SIZE);
      return cur_;
    }
  
    Allocator &get_allocator() { return *allocator_; }
  
    uoffset_t size() const {
      return static_cast<uoffset_t>(reserved_ - (cur_ - buf_));
    }
  
    size_t capacity() const { return reserved_; }
  
    uint8_t *buf() const {
      assert(buf_);
      return buf_;
    }
  
    uint8_t *data() const {
      assert(cur_);
      return cur_;
    }
  
    uint8_t *data_at(size_t offset) const { return buf_ + reserved_ - offset; }
  
    void push(const uint8_t *bytes, size_t num) {
      auto dest = make_space(num);
      memcpy(dest, bytes, num);
    }
  
    // Specialized version of push() that avoids memcpy call for small data.
    template<typename T> void push_small(const T &little_endian_t) {
      auto dest = make_space(sizeof(T));
      *reinterpret_cast<T *>(dest) = little_endian_t;
    }
  
    // fill() is most frequently called with small byte counts (<= 4),
    // which is why we're using loops rather than calling memset.
    void fill(size_t zero_pad_bytes) {
      auto dest = make_space(zero_pad_bytes);
      for (size_t i = 0; i < zero_pad_bytes; i++) dest[i] = 0;
    }
  
    // Version for when we know the size is larger.
    void fill_big(size_t zero_pad_bytes) {
      auto dest = make_space(zero_pad_bytes);
      memset(dest, 0, zero_pad_bytes);
    }
  
    void pop(size_t bytes_to_remove) { cur_ += bytes_to_remove; }
  
   private:
    // You shouldn't really be copying instances of this class.
    FLATBUFFERS_DELETE_FUNC(vector_downward(const vector_downward &))
    FLATBUFFERS_DELETE_FUNC(vector_downward &operator=(const vector_downward &))
  
    Allocator *allocator_;
    bool own_allocator_;
    size_t initial_size_;
    size_t reserved_;
    uint8_t *buf_;
    uint8_t *cur_;  // Points at location between empty (below) and used (above).
  
    void reallocate(size_t len) {
      assert(allocator_);
      auto old_reserved = reserved_;
      auto old_size = size();
      reserved_ += (std::max)(len, growth_policy(old_reserved));
      FLATBUFFERS_CONSTEXPR size_t alignment = AlignOf<largest_scalar_t>();
      reserved_ = (reserved_ + alignment - 1) & ~(alignment - 1);
      if (buf_) {
        buf_ = allocator_->reallocate_downward(buf_, old_reserved, reserved_);
      } else {
        buf_ = allocator_->allocate(reserved_);
      }
      cur_ = buf_ + reserved_ - old_size;
    }
  };
  
  // Converts a Field ID to a virtual table offset.
  inline voffset_t FieldIndexToOffset(voffset_t field_id) {
    // Should correspond to what EndTable() below builds up.
    const int fixed_fields = 2;  // Vtable size and Object Size.
    return static_cast<voffset_t>((field_id + fixed_fields) * sizeof(voffset_t));
  }
  
  template<typename T, typename Alloc>
  const T *data(const std::vector<T, Alloc> &v) {
    return v.empty() ? nullptr : &v.front();
  }
  template<typename T, typename Alloc> T *data(std::vector<T, Alloc> &v) {
    return v.empty() ? nullptr : &v.front();
  }
  
  /// @endcond
  
  /// @addtogroup flatbuffers_cpp_api
  /// @{
  /// @class FlatBufferBuilder
  /// @brief Helper class to hold data needed in creation of a FlatBuffer.
  /// To serialize data, you typically call one of the `Create*()` functions in
  /// the generated code, which in turn call a sequence of `StartTable`/
  /// `PushElement`/`AddElement`/`EndTable`, or the builtin `CreateString`/
  /// `CreateVector` functions. Do this is depth-first order to build up a tree to
  /// the root. `Finish()` wraps up the buffer ready for transport.
  class FlatBufferBuilder {
   public:
    /// @brief Default constructor for FlatBufferBuilder.
    /// @param[in] initial_size The initial size of the buffer, in bytes. Defaults
    /// to `1024`.
    /// @param[in] allocator An `Allocator` to use. Defaults to a new instance of
    /// a `DefaultAllocator`.
    /// @param[in] own_allocator Whether the builder/vector should own the
    /// allocator. Defaults to / `false`.
    explicit FlatBufferBuilder(size_t initial_size = 1024,
                               Allocator *allocator = nullptr,
                               bool own_allocator = false)
        : buf_(initial_size, allocator, own_allocator),
          max_voffset_(0),
          nested(false),
          finished(false),
          minalign_(1),
          force_defaults_(false),
          dedup_vtables_(true),
          string_pool(nullptr) {
      offsetbuf_.reserve(16);  // Avoid first few reallocs.
      vtables_.reserve(16);
      EndianCheck();
    }
  
    ~FlatBufferBuilder() {
      if (string_pool) delete string_pool;
    }
  
    void Reset() {
      Clear();       // clear builder state
      buf_.reset();  // deallocate buffer
    }
  
    /// @brief Reset all the state in this FlatBufferBuilder so it can be reused
    /// to construct another buffer.
    void Clear() {
      buf_.clear();
      ClearOffsets();
      nested = false;
      finished = false;
      vtables_.clear();
      minalign_ = 1;
      if (string_pool) string_pool->clear();
    }
  
    /// @brief The current size of the serialized buffer, counting from the end.
    /// @return Returns an `uoffset_t` with the current size of the buffer.
    uoffset_t GetSize() const { return buf_.size(); }
  
    /// @brief Get the serialized buffer (after you call `Finish()`).
    /// @return Returns an `uint8_t` pointer to the FlatBuffer data inside the
    /// buffer.
    uint8_t *GetBufferPointer() const {
      Finished();
      return buf_.data();
    }
  
    /// @brief Get a pointer to an unfinished buffer.
    /// @return Returns a `uint8_t` pointer to the unfinished buffer.
    uint8_t *GetCurrentBufferPointer() const { return buf_.data(); }
  
    /// @brief Get the released pointer to the serialized buffer.
    /// @warning Do NOT attempt to use this FlatBufferBuilder afterwards!
    /// @return A `FlatBuffer` that owns the buffer and its allocator and
    /// behaves similar to a `unique_ptr` with a deleter.
    /// Deprecated: use Release() instead
    DetachedBuffer ReleaseBufferPointer() {
      Finished();
      return buf_.release();
    }
  
    /// @brief Get the released DetachedBuffer.
    /// @return A `DetachedBuffer` that owns the buffer and its allocator.
    DetachedBuffer Release() {
      Finished();
      return buf_.release();
    }
  
    /// @brief get the minimum alignment this buffer needs to be accessed
    /// properly. This is only known once all elements have been written (after
    /// you call Finish()). You can use this information if you need to embed
    /// a FlatBuffer in some other buffer, such that you can later read it
    /// without first having to copy it into its own buffer.
    size_t GetBufferMinAlignment() {
      Finished();
      return minalign_;
    }
  
    /// @cond FLATBUFFERS_INTERNAL
    void Finished() const {
      // If you get this assert, you're attempting to get access a buffer
      // which hasn't been finished yet. Be sure to call
      // FlatBufferBuilder::Finish with your root table.
      // If you really need to access an unfinished buffer, call
      // GetCurrentBufferPointer instead.
      assert(finished);
    }
    /// @endcond
  
    /// @brief In order to save space, fields that are set to their default value
    /// don't get serialized into the buffer.
    /// @param[in] bool fd When set to `true`, always serializes default values.
    void ForceDefaults(bool fd) { force_defaults_ = fd; }
  
    /// @brief By default vtables are deduped in order to save space.
    /// @param[in] bool dedup When set to `true`, dedup vtables.
    void DedupVtables(bool dedup) { dedup_vtables_ = dedup; }
  
    /// @cond FLATBUFFERS_INTERNAL
    void Pad(size_t num_bytes) { buf_.fill(num_bytes); }
  
    void Align(size_t elem_size) {
      if (elem_size > minalign_) minalign_ = elem_size;
      buf_.fill(PaddingBytes(buf_.size(), elem_size));
    }
  
    void PushFlatBuffer(const uint8_t *bytes, size_t size) {
      PushBytes(bytes, size);
      finished = true;
    }
  
    void PushBytes(const uint8_t *bytes, size_t size) { buf_.push(bytes, size); }
  
    void PopBytes(size_t amount) { buf_.pop(amount); }
  
    template<typename T> void AssertScalarT() {
      // The code assumes power of 2 sizes and endian-swap-ability.
      static_assert(flatbuffers::is_scalar<T>::value, "T must be a scalar type");
    }
  
    // Write a single aligned scalar to the buffer
    template<typename T> uoffset_t PushElement(T element) {
      AssertScalarT<T>();
      T litle_endian_element = EndianScalar(element);
      Align(sizeof(T));
      buf_.push_small(litle_endian_element);
      return GetSize();
    }
  
    template<typename T> uoffset_t PushElement(Offset<T> off) {
      // Special case for offsets: see ReferTo below.
      return PushElement(ReferTo(off.o));
    }
  
    // When writing fields, we track where they are, so we can create correct
    // vtables later.
    void TrackField(voffset_t field, uoffset_t off) {
      FieldLoc fl = { off, field };
      offsetbuf_.push_back(fl);
      max_voffset_ = (std::max)(max_voffset_, field);
    }
  
    // Like PushElement, but additionally tracks the field this represents.
    template<typename T> void AddElement(voffset_t field, T e, T def) {
      // We don't serialize values equal to the default.
      if (e == def && !force_defaults_) return;
      auto off = PushElement(e);
      TrackField(field, off);
    }
  
    template<typename T> void AddOffset(voffset_t field, Offset<T> off) {
      if (off.IsNull()) return;  // Don't store.
      AddElement(field, ReferTo(off.o), static_cast<uoffset_t>(0));
    }
  
    template<typename T> void AddStruct(voffset_t field, const T *structptr) {
      if (!structptr) return;  // Default, don't store.
      Align(AlignOf<T>());
      buf_.push_small(*structptr);
      TrackField(field, GetSize());
    }
  
    void AddStructOffset(voffset_t field, uoffset_t off) {
      TrackField(field, off);
    }
  
    // Offsets initially are relative to the end of the buffer (downwards).
    // This function converts them to be relative to the current location
    // in the buffer (when stored here), pointing upwards.
    uoffset_t ReferTo(uoffset_t off) {
      // Align to ensure GetSize() below is correct.
      Align(sizeof(uoffset_t));
      // Offset must refer to something already in buffer.
      assert(off && off <= GetSize());
      return GetSize() - off + static_cast<uoffset_t>(sizeof(uoffset_t));
    }
  
    void NotNested() {
      // If you hit this, you're trying to construct a Table/Vector/String
      // during the construction of its parent table (between the MyTableBuilder
      // and table.Finish().
      // Move the creation of these sub-objects to above the MyTableBuilder to
      // not get this assert.
      // Ignoring this assert may appear to work in simple cases, but the reason
      // it is here is that storing objects in-line may cause vtable offsets
      // to not fit anymore. It also leads to vtable duplication.
      assert(!nested);
    }
  
    // From generated code (or from the parser), we call StartTable/EndTable
    // with a sequence of AddElement calls in between.
    uoffset_t StartTable() {
      NotNested();
      nested = true;
      return GetSize();
    }
  
    // This finishes one serialized object by generating the vtable if it's a
    // table, comparing it against existing vtables, and writing the
    // resulting vtable offset.
    uoffset_t EndTable(uoffset_t start) {
      // If you get this assert, a corresponding StartTable wasn't called.
      assert(nested);
      // Write the vtable offset, which is the start of any Table.
      // We fill it's value later.
      auto vtableoffsetloc = PushElement<soffset_t>(0);
      // Write a vtable, which consists entirely of voffset_t elements.
      // It starts with the number of offsets, followed by a type id, followed
      // by the offsets themselves. In reverse:
      // Include space for the last offset and ensure empty tables have a
      // minimum size.
      max_voffset_ =
          (std::max)(static_cast<voffset_t>(max_voffset_ + sizeof(voffset_t)),
                     FieldIndexToOffset(0));
      buf_.fill_big(max_voffset_);
      auto table_object_size = vtableoffsetloc - start;
      assert(table_object_size < 0x10000);  // Vtable use 16bit offsets.
      WriteScalar<voffset_t>(buf_.data() + sizeof(voffset_t),
                             static_cast<voffset_t>(table_object_size));
      WriteScalar<voffset_t>(buf_.data(), max_voffset_);
      // Write the offsets into the table
      for (auto field_location = offsetbuf_.begin();
           field_location != offsetbuf_.end(); ++field_location) {
        auto pos = static_cast<voffset_t>(vtableoffsetloc - field_location->off);
        // If this asserts, it means you've set a field twice.
        assert(!ReadScalar<voffset_t>(buf_.data() + field_location->id));
        WriteScalar<voffset_t>(buf_.data() + field_location->id, pos);
      }
      ClearOffsets();
      auto vt1 = reinterpret_cast<voffset_t *>(buf_.data());
      auto vt1_size = ReadScalar<voffset_t>(vt1);
      auto vt_use = GetSize();
      // See if we already have generated a vtable with this exact same
      // layout before. If so, make it point to the old one, remove this one.
      if (dedup_vtables_) {
        for (auto it = vtables_.begin(); it != vtables_.end(); ++it) {
          auto vt2 = reinterpret_cast<voffset_t *>(buf_.data_at(*it));
          auto vt2_size = *vt2;
          if (vt1_size != vt2_size || memcmp(vt2, vt1, vt1_size)) continue;
          vt_use = *it;
          buf_.pop(GetSize() - vtableoffsetloc);
          break;
        }
      }
      // If this is a new vtable, remember it.
      if (vt_use == GetSize()) { vtables_.push_back(vt_use); }
      // Fill the vtable offset we created above.
      // The offset points from the beginning of the object to where the
      // vtable is stored.
      // Offsets default direction is downward in memory for future format
      // flexibility (storing all vtables at the start of the file).
      WriteScalar(buf_.data_at(vtableoffsetloc),
                  static_cast<soffset_t>(vt_use) -
                      static_cast<soffset_t>(vtableoffsetloc));
  
      nested = false;
      return vtableoffsetloc;
    }
  
    // DEPRECATED: call the version above instead.
    uoffset_t EndTable(uoffset_t start, voffset_t /*numfields*/) {
      return EndTable(start);
    }
  
    // This checks a required field has been set in a given table that has
    // just been constructed.
    template<typename T> void Required(Offset<T> table, voffset_t field) {
      auto table_ptr = buf_.data_at(table.o);
      auto vtable_ptr = table_ptr - ReadScalar<soffset_t>(table_ptr);
      bool ok = ReadScalar<voffset_t>(vtable_ptr + field) != 0;
      // If this fails, the caller will show what field needs to be set.
      assert(ok);
      (void)ok;
    }
  
    uoffset_t StartStruct(size_t alignment) {
      Align(alignment);
      return GetSize();
    }
  
    uoffset_t EndStruct() { return GetSize(); }
  
    void ClearOffsets() {
      offsetbuf_.clear();
      max_voffset_ = 0;
    }
  
    // Aligns such that when "len" bytes are written, an object can be written
    // after it with "alignment" without padding.
    void PreAlign(size_t len, size_t alignment) {
      buf_.fill(PaddingBytes(GetSize() + len, alignment));
    }
    template<typename T> void PreAlign(size_t len) {
      AssertScalarT<T>();
      PreAlign(len, sizeof(T));
    }
    /// @endcond
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// @param[in] str A const char pointer to the data to be stored as a string.
    /// @param[in] len The number of bytes that should be stored from `str`.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateString(const char *str, size_t len) {
      NotNested();
      PreAlign<uoffset_t>(len + 1);  // Always 0-terminated.
      buf_.fill(1);
      PushBytes(reinterpret_cast<const uint8_t *>(str), len);
      PushElement(static_cast<uoffset_t>(len));
      return Offset<String>(GetSize());
    }
  
    /// @brief Store a string in the buffer, which is null-terminated.
    /// @param[in] str A const char pointer to a C-string to add to the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateString(const char *str) {
      return CreateString(str, strlen(str));
    }
  
    /// @brief Store a string in the buffer, which is null-terminated.
    /// @param[in] str A char pointer to a C-string to add to the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateString(char *str) {
      return CreateString(str, strlen(str));
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// @param[in] str A const reference to a std::string to store in the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateString(const std::string &str) {
      return CreateString(str.c_str(), str.length());
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// @param[in] str A const pointer to a `String` struct to add to the buffer.
    /// @return Returns the offset in the buffer where the string starts
    Offset<String> CreateString(const String *str) {
      return str ? CreateString(str->c_str(), str->Length()) : 0;
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// @param[in] str A const reference to a std::string like type with support
    /// of T::c_str() and T::length() to store in the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    template<typename T> Offset<String> CreateString(const T &str) {
      return CreateString(str.c_str(), str.length());
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// If a string with this exact contents has already been serialized before,
    /// instead simply returns the offset of the existing string.
    /// @param[in] str A const char pointer to the data to be stored as a string.
    /// @param[in] len The number of bytes that should be stored from `str`.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateSharedString(const char *str, size_t len) {
      if (!string_pool)
        string_pool = new StringOffsetMap(StringOffsetCompare(buf_));
      auto size_before_string = buf_.size();
      // Must first serialize the string, since the set is all offsets into
      // buffer.
      auto off = CreateString(str, len);
      auto it = string_pool->find(off);
      // If it exists we reuse existing serialized data!
      if (it != string_pool->end()) {
        // We can remove the string we serialized.
        buf_.pop(buf_.size() - size_before_string);
        return *it;
      }
      // Record this string for future use.
      string_pool->insert(off);
      return off;
    }
  
    /// @brief Store a string in the buffer, which null-terminated.
    /// If a string with this exact contents has already been serialized before,
    /// instead simply returns the offset of the existing string.
    /// @param[in] str A const char pointer to a C-string to add to the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateSharedString(const char *str) {
      return CreateSharedString(str, strlen(str));
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// If a string with this exact contents has already been serialized before,
    /// instead simply returns the offset of the existing string.
    /// @param[in] str A const reference to a std::string to store in the buffer.
    /// @return Returns the offset in the buffer where the string starts.
    Offset<String> CreateSharedString(const std::string &str) {
      return CreateSharedString(str.c_str(), str.length());
    }
  
    /// @brief Store a string in the buffer, which can contain any binary data.
    /// If a string with this exact contents has already been serialized before,
    /// instead simply returns the offset of the existing string.
    /// @param[in] str A const pointer to a `String` struct to add to the buffer.
    /// @return Returns the offset in the buffer where the string starts
    Offset<String> CreateSharedString(const String *str) {
      return CreateSharedString(str->c_str(), str->Length());
    }
  
    /// @cond FLATBUFFERS_INTERNAL
    uoffset_t EndVector(size_t len) {
      assert(nested);  // Hit if no corresponding StartVector.
      nested = false;
      return PushElement(static_cast<uoffset_t>(len));
    }
  
    void StartVector(size_t len, size_t elemsize) {
      NotNested();
      nested = true;
      PreAlign<uoffset_t>(len * elemsize);
      PreAlign(len * elemsize, elemsize);  // Just in case elemsize > uoffset_t.
    }
  
    // Call this right before StartVector/CreateVector if you want to force the
    // alignment to be something different than what the element size would
    // normally dictate.
    // This is useful when storing a nested_flatbuffer in a vector of bytes,
    // or when storing SIMD floats, etc.
    void ForceVectorAlignment(size_t len, size_t elemsize, size_t alignment) {
      PreAlign(len * elemsize, alignment);
    }
  
    uint8_t *ReserveElements(size_t len, size_t elemsize) {
      return buf_.make_space(len * elemsize);
    }
    /// @endcond
  
    /// @brief Serialize an array into a FlatBuffer `vector`.
    /// @tparam T The data type of the array elements.
    /// @param[in] v A pointer to the array of type `T` to serialize into the
    /// buffer as a `vector`.
    /// @param[in] len The number of elements to serialize.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T> Offset<Vector<T>> CreateVector(const T *v, size_t len) {
      // If this assert hits, you're specifying a template argument that is
      // causing the wrong overload to be selected, remove it.
      AssertScalarT<T>();
      StartVector(len, sizeof(T));
      // clang-format off
      #if FLATBUFFERS_LITTLEENDIAN
        PushBytes(reinterpret_cast<const uint8_t *>(v), len * sizeof(T));
      #else
        if (sizeof(T) == 1) {
          PushBytes(reinterpret_cast<const uint8_t *>(v), len);
        } else {
          for (auto i = len; i > 0; ) {
            PushElement(v[--i]);
          }
        }
      #endif
      // clang-format on
      return Offset<Vector<T>>(EndVector(len));
    }
  
    template<typename T>
    Offset<Vector<Offset<T>>> CreateVector(const Offset<T> *v, size_t len) {
      StartVector(len, sizeof(Offset<T>));
      for (auto i = len; i > 0;) { PushElement(v[--i]); }
      return Offset<Vector<Offset<T>>>(EndVector(len));
    }
  
    /// @brief Serialize a `std::vector` into a FlatBuffer `vector`.
    /// @tparam T The data type of the `std::vector` elements.
    /// @param v A const reference to the `std::vector` to serialize into the
    /// buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T> Offset<Vector<T>> CreateVector(const std::vector<T> &v) {
      return CreateVector(data(v), v.size());
    }
  
    // vector<bool> may be implemented using a bit-set, so we can't access it as
    // an array. Instead, read elements manually.
    // Background: https://isocpp.org/blog/2012/11/on-vectorbool
    Offset<Vector<uint8_t>> CreateVector(const std::vector<bool> &v) {
      StartVector(v.size(), sizeof(uint8_t));
      for (auto i = v.size(); i > 0;) {
        PushElement(static_cast<uint8_t>(v[--i]));
      }
      return Offset<Vector<uint8_t>>(EndVector(v.size()));
    }
  
    // clang-format off
    #ifndef FLATBUFFERS_CPP98_STL
    /// @brief Serialize values returned by a function into a FlatBuffer `vector`.
    /// This is a convenience function that takes care of iteration for you.
    /// @tparam T The data type of the `std::vector` elements.
    /// @param f A function that takes the current iteration 0..vector_size-1 and
    /// returns any type that you can construct a FlatBuffers vector out of.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T> Offset<Vector<T>> CreateVector(size_t vector_size,
        const std::function<T (size_t i)> &f) {
      std::vector<T> elems(vector_size);
      for (size_t i = 0; i < vector_size; i++) elems[i] = f(i);
      return CreateVector(elems);
    }
    #endif
    // clang-format on
  
    /// @brief Serialize values returned by a function into a FlatBuffer `vector`.
    /// This is a convenience function that takes care of iteration for you.
    /// @tparam T The data type of the `std::vector` elements.
    /// @param f A function that takes the current iteration 0..vector_size-1,
    /// and the state parameter returning any type that you can construct a
    /// FlatBuffers vector out of.
    /// @param state State passed to f.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename F, typename S>
    Offset<Vector<T>> CreateVector(size_t vector_size, F f, S *state) {
      std::vector<T> elems(vector_size);
      for (size_t i = 0; i < vector_size; i++) elems[i] = f(i, state);
      return CreateVector(elems);
    }
  
    /// @brief Serialize a `std::vector<std::string>` into a FlatBuffer `vector`.
    /// This is a convenience function for a common case.
    /// @param v A const reference to the `std::vector` to serialize into the
    /// buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    Offset<Vector<Offset<String>>> CreateVectorOfStrings(
        const std::vector<std::string> &v) {
      std::vector<Offset<String>> offsets(v.size());
      for (size_t i = 0; i < v.size(); i++) offsets[i] = CreateString(v[i]);
      return CreateVector(offsets);
    }
  
    /// @brief Serialize an array of structs into a FlatBuffer `vector`.
    /// @tparam T The data type of the struct array elements.
    /// @param[in] v A pointer to the array of type `T` to serialize into the
    /// buffer as a `vector`.
    /// @param[in] len The number of elements to serialize.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T>
    Offset<Vector<const T *>> CreateVectorOfStructs(const T *v, size_t len) {
      StartVector(len * sizeof(T) / AlignOf<T>(), AlignOf<T>());
      PushBytes(reinterpret_cast<const uint8_t *>(v), sizeof(T) * len);
      return Offset<Vector<const T *>>(EndVector(len));
    }
  
    /// @brief Serialize an array of native structs into a FlatBuffer `vector`.
    /// @tparam T The data type of the struct array elements.
    /// @tparam S The data type of the native struct array elements.
    /// @param[in] v A pointer to the array of type `S` to serialize into the
    /// buffer as a `vector`.
    /// @param[in] len The number of elements to serialize.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename S>
    Offset<Vector<const T *>> CreateVectorOfNativeStructs(const S *v,
                                                          size_t len) {
      extern T Pack(const S &);
      typedef T (*Pack_t)(const S &);
      std::vector<T> vv(len);
      std::transform(v, v + len, vv.begin(), *(Pack_t)&Pack);
      return CreateVectorOfStructs<T>(vv.data(), vv.size());
    }
  
    // clang-format off
    #ifndef FLATBUFFERS_CPP98_STL
    /// @brief Serialize an array of structs into a FlatBuffer `vector`.
    /// @tparam T The data type of the struct array elements.
    /// @param[in] f A function that takes the current iteration 0..vector_size-1
    /// and a pointer to the struct that must be filled.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    /// This is mostly useful when flatbuffers are generated with mutation
    /// accessors.
    template<typename T> Offset<Vector<const T *>> CreateVectorOfStructs(
        size_t vector_size, const std::function<void(size_t i, T *)> &filler) {
      T* structs = StartVectorOfStructs<T>(vector_size);
      for (size_t i = 0; i < vector_size; i++) {
        filler(i, structs);
        structs++;
      }
      return EndVectorOfStructs<T>(vector_size);
    }
    #endif
    // clang-format on
  
    /// @brief Serialize an array of structs into a FlatBuffer `vector`.
    /// @tparam T The data type of the struct array elements.
    /// @param[in] f A function that takes the current iteration 0..vector_size-1,
    /// a pointer to the struct that must be filled and the state argument.
    /// @param[in] state Arbitrary state to pass to f.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    /// This is mostly useful when flatbuffers are generated with mutation
    /// accessors.
    template<typename T, typename F, typename S>
    Offset<Vector<const T *>> CreateVectorOfStructs(size_t vector_size, F f,
                                                    S *state) {
      T *structs = StartVectorOfStructs<T>(vector_size);
      for (size_t i = 0; i < vector_size; i++) {
        f(i, structs, state);
        structs++;
      }
      return EndVectorOfStructs<T>(vector_size);
    }
  
    /// @brief Serialize a `std::vector` of structs into a FlatBuffer `vector`.
    /// @tparam T The data type of the `std::vector` struct elements.
    /// @param[in]] v A const reference to the `std::vector` of structs to
    /// serialize into the buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename Alloc>
    Offset<Vector<const T *>> CreateVectorOfStructs(
        const std::vector<T, Alloc> &v) {
      return CreateVectorOfStructs(data(v), v.size());
    }
  
    /// @brief Serialize a `std::vector` of native structs into a FlatBuffer
    /// `vector`.
    /// @tparam T The data type of the `std::vector` struct elements.
    /// @tparam S The data type of the `std::vector` native struct elements.
    /// @param[in]] v A const reference to the `std::vector` of structs to
    /// serialize into the buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename S>
    Offset<Vector<const T *>> CreateVectorOfNativeStructs(
        const std::vector<S> &v) {
      return CreateVectorOfNativeStructs<T, S>(data(v), v.size());
    }
  
    /// @cond FLATBUFFERS_INTERNAL
    template<typename T> struct StructKeyComparator {
      bool operator()(const T &a, const T &b) const {
        return a.KeyCompareLessThan(&b);
      }
  
     private:
      StructKeyComparator &operator=(const StructKeyComparator &);
    };
    /// @endcond
  
    /// @brief Serialize a `std::vector` of structs into a FlatBuffer `vector`
    /// in sorted order.
    /// @tparam T The data type of the `std::vector` struct elements.
    /// @param[in]] v A const reference to the `std::vector` of structs to
    /// serialize into the buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T>
    Offset<Vector<const T *>> CreateVectorOfSortedStructs(std::vector<T> *v) {
      return CreateVectorOfSortedStructs(data(*v), v->size());
    }
  
    /// @brief Serialize a `std::vector` of native structs into a FlatBuffer
    /// `vector` in sorted order.
    /// @tparam T The data type of the `std::vector` struct elements.
    /// @tparam S The data type of the `std::vector` native struct elements.
    /// @param[in]] v A const reference to the `std::vector` of structs to
    /// serialize into the buffer as a `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename S>
    Offset<Vector<const T *>> CreateVectorOfSortedNativeStructs(
        std::vector<S> *v) {
      return CreateVectorOfSortedNativeStructs<T, S>(data(*v), v->size());
    }
  
    /// @brief Serialize an array of structs into a FlatBuffer `vector` in sorted
    /// order.
    /// @tparam T The data type of the struct array elements.
    /// @param[in] v A pointer to the array of type `T` to serialize into the
    /// buffer as a `vector`.
    /// @param[in] len The number of elements to serialize.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T>
    Offset<Vector<const T *>> CreateVectorOfSortedStructs(T *v, size_t len) {
      std::sort(v, v + len, StructKeyComparator<T>());
      return CreateVectorOfStructs(v, len);
    }
  
    /// @brief Serialize an array of native structs into a FlatBuffer `vector` in
    /// sorted order.
    /// @tparam T The data type of the struct array elements.
    /// @tparam S The data type of the native struct array elements.
    /// @param[in] v A pointer to the array of type `S` to serialize into the
    /// buffer as a `vector`.
    /// @param[in] len The number of elements to serialize.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T, typename S>
    Offset<Vector<const T *>> CreateVectorOfSortedNativeStructs(S *v,
                                                                size_t len) {
      extern T Pack(const S &);
      typedef T (*Pack_t)(const S &);
      std::vector<T> vv(len);
      std::transform(v, v + len, vv.begin(), *(Pack_t)&Pack);
      return CreateVectorOfSortedStructs<T>(vv, len);
    }
  
    /// @cond FLATBUFFERS_INTERNAL
    template<typename T> struct TableKeyComparator {
      TableKeyComparator(vector_downward &buf) : buf_(buf) {}
      bool operator()(const Offset<T> &a, const Offset<T> &b) const {
        auto table_a = reinterpret_cast<T *>(buf_.data_at(a.o));
        auto table_b = reinterpret_cast<T *>(buf_.data_at(b.o));
        return table_a->KeyCompareLessThan(table_b);
      }
      vector_downward &buf_;
  
     private:
      TableKeyComparator &operator=(const TableKeyComparator &);
    };
    /// @endcond
  
    /// @brief Serialize an array of `table` offsets as a `vector` in the buffer
    /// in sorted order.
    /// @tparam T The data type that the offset refers to.
    /// @param[in] v An array of type `Offset<T>` that contains the `table`
    /// offsets to store in the buffer in sorted order.
    /// @param[in] len The number of elements to store in the `vector`.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T>
    Offset<Vector<Offset<T>>> CreateVectorOfSortedTables(Offset<T> *v,
                                                         size_t len) {
      std::sort(v, v + len, TableKeyComparator<T>(buf_));
      return CreateVector(v, len);
    }
  
    /// @brief Serialize an array of `table` offsets as a `vector` in the buffer
    /// in sorted order.
    /// @tparam T The data type that the offset refers to.
    /// @param[in] v An array of type `Offset<T>` that contains the `table`
    /// offsets to store in the buffer in sorted order.
    /// @return Returns a typed `Offset` into the serialized data indicating
    /// where the vector is stored.
    template<typename T>
    Offset<Vector<Offset<T>>> CreateVectorOfSortedTables(
        std::vector<Offset<T>> *v) {
      return CreateVectorOfSortedTables(data(*v), v->size());
    }
  
    /// @brief Specialized version of `CreateVector` for non-copying use cases.
    /// Write the data any time later to the returned buffer pointer `buf`.
    /// @param[in] len The number of elements to store in the `vector`.
    /// @param[in] elemsize The size of each element in the `vector`.
    /// @param[out] buf A pointer to a `uint8_t` pointer that can be
    /// written to at a later time to serialize the data into a `vector`
    /// in the buffer.
    uoffset_t CreateUninitializedVector(size_t len, size_t elemsize,
                                        uint8_t **buf) {
      NotNested();
      StartVector(len, elemsize);
      buf_.make_space(len * elemsize);
      auto vec_start = GetSize();
      auto vec_end = EndVector(len);
      *buf = buf_.data_at(vec_start);
      return vec_end;
    }
  
    /// @brief Specialized version of `CreateVector` for non-copying use cases.
    /// Write the data any time later to the returned buffer pointer `buf`.
    /// @tparam T The data type of the data that will be stored in the buffer
    /// as a `vector`.
    /// @param[in] len The number of elements to store in the `vector`.
    /// @param[out] buf A pointer to a pointer of type `T` that can be
    /// written to at a later time to serialize the data into a `vector`
    /// in the buffer.
    template<typename T>
    Offset<Vector<T>> CreateUninitializedVector(size_t len, T **buf) {
      return CreateUninitializedVector(len, sizeof(T),
                                       reinterpret_cast<uint8_t **>(buf));
    }
  
    /// @brief Write a struct by itself, typically to be part of a union.
    template<typename T> Offset<const T *> CreateStruct(const T &structobj) {
      NotNested();
      Align(AlignOf<T>());
      buf_.push_small(structobj);
      return Offset<const T *>(GetSize());
    }
  
    /// @brief The length of a FlatBuffer file header.
    static const size_t kFileIdentifierLength = 4;
  
    /// @brief Finish serializing a buffer by writing the root offset.
    /// @param[in] file_identifier If a `file_identifier` is given, the buffer
    /// will be prefixed with a standard FlatBuffers file header.
    template<typename T>
    void Finish(Offset<T> root, const char *file_identifier = nullptr) {
      Finish(root.o, file_identifier, false);
    }
  
    /// @brief Finish a buffer with a 32 bit size field pre-fixed (size of the
    /// buffer following the size field). These buffers are NOT compatible
    /// with standard buffers created by Finish, i.e. you can't call GetRoot
    /// on them, you have to use GetSizePrefixedRoot instead.
    /// All >32 bit quantities in this buffer will be aligned when the whole
    /// size pre-fixed buffer is aligned.
    /// These kinds of buffers are useful for creating a stream of FlatBuffers.
    template<typename T>
    void FinishSizePrefixed(Offset<T> root,
                            const char *file_identifier = nullptr) {
      Finish(root.o, file_identifier, true);
    }
  
   protected:
    // You shouldn't really be copying instances of this class.
    FlatBufferBuilder(const FlatBufferBuilder &);
    FlatBufferBuilder &operator=(const FlatBufferBuilder &);
  
    void Finish(uoffset_t root, const char *file_identifier, bool size_prefix) {
      NotNested();
      // This will cause the whole buffer to be aligned.
      PreAlign((size_prefix ? sizeof(uoffset_t) : 0) + sizeof(uoffset_t) +
                   (file_identifier ? kFileIdentifierLength : 0),
               minalign_);
      if (file_identifier) {
        assert(strlen(file_identifier) == kFileIdentifierLength);
        PushBytes(reinterpret_cast<const uint8_t *>(file_identifier),
                  kFileIdentifierLength);
      }
      PushElement(ReferTo(root));  // Location of root.
      if (size_prefix) { PushElement(GetSize()); }
      finished = true;
    }
  
    struct FieldLoc {
      uoffset_t off;
      voffset_t id;
    };
  
    vector_downward buf_;
  
    // Accumulating offsets of table members while it is being built.
    std::vector<FieldLoc> offsetbuf_;
    // Track how much of the vtable is in use, so we can output the most compact
    // possible vtable.
    voffset_t max_voffset_;
  
    // Ensure objects are not nested.
    bool nested;
  
    // Ensure the buffer is finished before it is being accessed.
    bool finished;
  
    std::vector<uoffset_t> vtables_;  // todo: Could make this into a map?
  
    size_t minalign_;
  
    bool force_defaults_;  // Serialize values equal to their defaults anyway.
  
    bool dedup_vtables_;
  
    struct StringOffsetCompare {
      StringOffsetCompare(const vector_downward &buf) : buf_(&buf) {}
      bool operator()(const Offset<String> &a, const Offset<String> &b) const {
        auto stra = reinterpret_cast<const String *>(buf_->data_at(a.o));
        auto strb = reinterpret_cast<const String *>(buf_->data_at(b.o));
        return strncmp(stra->c_str(), strb->c_str(),
                       (std::min)(stra->size(), strb->size()) + 1) < 0;
      }
      const vector_downward *buf_;
    };
  
    // For use with CreateSharedString. Instantiated on first use only.
    typedef std::set<Offset<String>, StringOffsetCompare> StringOffsetMap;
    StringOffsetMap *string_pool;
  
   private:
    // Allocates space for a vector of structures.
    // Must be completed with EndVectorOfStructs().
    template<typename T> T *StartVectorOfStructs(size_t vector_size) {
      StartVector(vector_size * sizeof(T) / AlignOf<T>(), AlignOf<T>());
      return reinterpret_cast<T *>(buf_.make_space(vector_size * sizeof(T)));
    }
  
    // End the vector of structues in the flatbuffers.
    // Vector should have previously be started with StartVectorOfStructs().
    template<typename T>
    Offset<Vector<const T *>> EndVectorOfStructs(size_t vector_size) {
      return Offset<Vector<const T *>>(EndVector(vector_size));
    }
  };
  /// @}
  
  /// @cond FLATBUFFERS_INTERNAL
  // Helpers to get a typed pointer to the root object contained in the buffer.
  template<typename T> T *GetMutableRoot(void *buf) {
    EndianCheck();
    return reinterpret_cast<T *>(
        reinterpret_cast<uint8_t *>(buf) +
        EndianScalar(*reinterpret_cast<uoffset_t *>(buf)));
  }
  
  template<typename T> const T *GetRoot(const void *buf) {
    return GetMutableRoot<T>(const_cast<void *>(buf));
  }
  
  template<typename T> const T *GetSizePrefixedRoot(const void *buf) {
    return GetRoot<T>(reinterpret_cast<const uint8_t *>(buf) + sizeof(uoffset_t));
  }
  
  /// Helpers to get a typed pointer to objects that are currently being built.
  /// @warning Creating new objects will lead to reallocations and invalidates
  /// the pointer!
  template<typename T>
  T *GetMutableTemporaryPointer(FlatBufferBuilder &fbb, Offset<T> offset) {
    return reinterpret_cast<T *>(fbb.GetCurrentBufferPointer() + fbb.GetSize() -
                                 offset.o);
  }
  
  template<typename T>
  const T *GetTemporaryPointer(FlatBufferBuilder &fbb, Offset<T> offset) {
    return GetMutableTemporaryPointer<T>(fbb, offset);
  }
  
  /// @brief Get a pointer to the the file_identifier section of the buffer.
  /// @return Returns a const char pointer to the start of the file_identifier
  /// characters in the buffer.  The returned char * has length
  /// 'flatbuffers::FlatBufferBuilder::kFileIdentifierLength'.
  /// This function is UNDEFINED for FlatBuffers whose schema does not include
  /// a file_identifier (likely points at padding or the start of a the root
  /// vtable).
  inline const char *GetBufferIdentifier(const void *buf) {
    return reinterpret_cast<const char *>(buf) + sizeof(uoffset_t);
  }
  
  // Helper to see if the identifier in a buffer has the expected value.
  inline bool BufferHasIdentifier(const void *buf, const char *identifier) {
    return strncmp(GetBufferIdentifier(buf), identifier,
                   FlatBufferBuilder::kFileIdentifierLength) == 0;
  }
  
  // Helper class to verify the integrity of a FlatBuffer
  class Verifier FLATBUFFERS_FINAL_CLASS {
   public:
    Verifier(const uint8_t *buf, size_t buf_len, uoffset_t _max_depth = 64,
             uoffset_t _max_tables = 1000000)
        : buf_(buf),
          end_(buf + buf_len),
          depth_(0),
          max_depth_(_max_depth),
          num_tables_(0),
          max_tables_(_max_tables)
    // clang-format off
      #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
          , upper_bound_(buf)
      #endif
    // clang-format on
    {
    }
  
    // Central location where any verification failures register.
    bool Check(bool ok) const {
      // clang-format off
      #ifdef FLATBUFFERS_DEBUG_VERIFICATION_FAILURE
        assert(ok);
      #endif
      #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
        if (!ok)
          upper_bound_ = buf_;
      #endif
      // clang-format on
      return ok;
    }
  
    // Verify any range within the buffer.
    bool Verify(const void *elem, size_t elem_len) const {
      // clang-format off
      #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
        auto upper_bound = reinterpret_cast<const uint8_t *>(elem) + elem_len;
        if (upper_bound_ < upper_bound)
          upper_bound_ =  upper_bound;
      #endif
      // clang-format on
      return Check(elem_len <= (size_t)(end_ - buf_) && elem >= buf_ &&
                   elem <= end_ - elem_len);
    }
  
    // Verify a range indicated by sizeof(T).
    template<typename T> bool Verify(const void *elem) const {
      return Verify(elem, sizeof(T));
    }
  
    // Verify a pointer (may be NULL) of a table type.
    template<typename T> bool VerifyTable(const T *table) {
      return !table || table->Verify(*this);
    }
  
    // Verify a pointer (may be NULL) of any vector type.
    template<typename T> bool Verify(const Vector<T> *vec) const {
      const uint8_t *end;
      return !vec || VerifyVector(reinterpret_cast<const uint8_t *>(vec),
                                  sizeof(T), &end);
    }
  
    // Verify a pointer (may be NULL) of a vector to struct.
    template<typename T> bool Verify(const Vector<const T *> *vec) const {
      return Verify(reinterpret_cast<const Vector<T> *>(vec));
    }
  
    // Verify a pointer (may be NULL) to string.
    bool Verify(const String *str) const {
      const uint8_t *end;
      return !str ||
             (VerifyVector(reinterpret_cast<const uint8_t *>(str), 1, &end) &&
              Verify(end, 1) &&      // Must have terminator
              Check(*end == '\0'));  // Terminating byte must be 0.
    }
  
    // Common code between vectors and strings.
    bool VerifyVector(const uint8_t *vec, size_t elem_size,
                      const uint8_t **end) const {
      // Check we can read the size field.
      if (!Verify<uoffset_t>(vec)) return false;
      // Check the whole array. If this is a string, the byte past the array
      // must be 0.
      auto size = ReadScalar<uoffset_t>(vec);
      auto max_elems = FLATBUFFERS_MAX_BUFFER_SIZE / elem_size;
      if (!Check(size < max_elems))
        return false;  // Protect against byte_size overflowing.
      auto byte_size = sizeof(size) + elem_size * size;
      *end = vec + byte_size;
      return Verify(vec, byte_size);
    }
  
    // Special case for string contents, after the above has been called.
    bool VerifyVectorOfStrings(const Vector<Offset<String>> *vec) const {
      if (vec) {
        for (uoffset_t i = 0; i < vec->size(); i++) {
          if (!Verify(vec->Get(i))) return false;
        }
      }
      return true;
    }
  
    // Special case for table contents, after the above has been called.
    template<typename T> bool VerifyVectorOfTables(const Vector<Offset<T>> *vec) {
      if (vec) {
        for (uoffset_t i = 0; i < vec->size(); i++) {
          if (!vec->Get(i)->Verify(*this)) return false;
        }
      }
      return true;
    }
  
    template<typename T>
    bool VerifyBufferFromStart(const char *identifier, const uint8_t *start) {
      if (identifier &&
          (size_t(end_ - start) < 2 * sizeof(flatbuffers::uoffset_t) ||
           !BufferHasIdentifier(start, identifier))) {
        return false;
      }
  
      // Call T::Verify, which must be in the generated code for this type.
      auto o = VerifyOffset(start);
      return o && reinterpret_cast<const T *>(start + o)->Verify(*this)
  #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
             && GetComputedSize()
  #endif
          ;
    }
  
    // Verify this whole buffer, starting with root type T.
    template<typename T> bool VerifyBuffer() { return VerifyBuffer<T>(nullptr); }
  
    template<typename T> bool VerifyBuffer(const char *identifier) {
      return VerifyBufferFromStart<T>(identifier, buf_);
    }
  
    template<typename T> bool VerifySizePrefixedBuffer(const char *identifier) {
      return Verify<uoffset_t>(buf_) &&
             ReadScalar<uoffset_t>(buf_) == end_ - buf_ - sizeof(uoffset_t) &&
             VerifyBufferFromStart<T>(identifier, buf_ + sizeof(uoffset_t));
    }
  
    uoffset_t VerifyOffset(const uint8_t *start) const {
      if (!Verify<uoffset_t>(start)) return false;
      auto o = ReadScalar<uoffset_t>(start);
      Check(o != 0);
      return o;
    }
  
    // Called at the start of a table to increase counters measuring data
    // structure depth and amount, and possibly bails out with false if
    // limits set by the constructor have been hit. Needs to be balanced
    // with EndTable().
    bool VerifyComplexity() {
      depth_++;
      num_tables_++;
      return Check(depth_ <= max_depth_ && num_tables_ <= max_tables_);
    }
  
    // Called at the end of a table to pop the depth count.
    bool EndTable() {
      depth_--;
      return true;
    }
  
    // clang-format off
    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
    // Returns the message size in bytes
    size_t GetComputedSize() const {
      uintptr_t size = upper_bound_ - buf_;
      // Align the size to uoffset_t
      size = (size - 1 + sizeof(uoffset_t)) & ~(sizeof(uoffset_t) - 1);
      return (buf_  + size > end_) ?  0 : size;
    }
    #endif
    // clang-format on
  
   private:
    const uint8_t *buf_;
    const uint8_t *end_;
    uoffset_t depth_;
    uoffset_t max_depth_;
    uoffset_t num_tables_;
    uoffset_t max_tables_;
    // clang-format off
    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
      mutable const uint8_t *upper_bound_;
    #endif
    // clang-format on
  };
  
  // Convenient way to bundle a buffer and its length, to pass it around
  // typed by its root.
  // A BufferRef does not own its buffer.
  struct BufferRefBase {};  // for std::is_base_of
  template<typename T> struct BufferRef : BufferRefBase {
    BufferRef() : buf(nullptr), len(0), must_free(false) {}
    BufferRef(uint8_t *_buf, uoffset_t _len)
        : buf(_buf), len(_len), must_free(false) {}
  
    ~BufferRef() {
      if (must_free) free(buf);
    }
  
    const T *GetRoot() const { return flatbuffers::GetRoot<T>(buf); }
  
    bool Verify() {
      Verifier verifier(buf, len);
      return verifier.VerifyBuffer<T>(nullptr);
    }
  
    uint8_t *buf;
    uoffset_t len;
    bool must_free;
  };
  
  // "structs" are flat structures that do not have an offset table, thus
  // always have all members present and do not support forwards/backwards
  // compatible extensions.
  
  class Struct FLATBUFFERS_FINAL_CLASS {
   public:
    template<typename T> T GetField(uoffset_t o) const {
      return ReadScalar<T>(&data_[o]);
    }
  
    template<typename T> T GetStruct(uoffset_t o) const {
      return reinterpret_cast<T>(&data_[o]);
    }
  
    const uint8_t *GetAddressOf(uoffset_t o) const { return &data_[o]; }
    uint8_t *GetAddressOf(uoffset_t o) { return &data_[o]; }
  
   private:
    uint8_t data_[1];
  };
  
  // "tables" use an offset table (possibly shared) that allows fields to be
  // omitted and added at will, but uses an extra indirection to read.
  class Table {
   public:
    const uint8_t *GetVTable() const {
      return data_ - ReadScalar<soffset_t>(data_);
    }
  
    // This gets the field offset for any of the functions below it, or 0
    // if the field was not present.
    voffset_t GetOptionalFieldOffset(voffset_t field) const {
      // The vtable offset is always at the start.
      auto vtable = GetVTable();
      // The first element is the size of the vtable (fields + type id + itself).
      auto vtsize = ReadScalar<voffset_t>(vtable);
      // If the field we're accessing is outside the vtable, we're reading older
      // data, so it's the same as if the offset was 0 (not present).
      return field < vtsize ? ReadScalar<voffset_t>(vtable + field) : 0;
    }
  
    template<typename T> T GetField(voffset_t field, T defaultval) const {
      auto field_offset = GetOptionalFieldOffset(field);
      return field_offset ? ReadScalar<T>(data_ + field_offset) : defaultval;
    }
  
    template<typename P> P GetPointer(voffset_t field) {
      auto field_offset = GetOptionalFieldOffset(field);
      auto p = data_ + field_offset;
      return field_offset ? reinterpret_cast<P>(p + ReadScalar<uoffset_t>(p))
                          : nullptr;
    }
    template<typename P> P GetPointer(voffset_t field) const {
      return const_cast<Table *>(this)->GetPointer<P>(field);
    }
  
    template<typename P> P GetStruct(voffset_t field) const {
      auto field_offset = GetOptionalFieldOffset(field);
      auto p = const_cast<uint8_t *>(data_ + field_offset);
      return field_offset ? reinterpret_cast<P>(p) : nullptr;
    }
  
    template<typename T> bool SetField(voffset_t field, T val, T def) {
      auto field_offset = GetOptionalFieldOffset(field);
      if (!field_offset) return val == def;
      WriteScalar(data_ + field_offset, val);
      return true;
    }
  
    bool SetPointer(voffset_t field, const uint8_t *val) {
      auto field_offset = GetOptionalFieldOffset(field);
      if (!field_offset) return false;
      WriteScalar(data_ + field_offset,
                  static_cast<uoffset_t>(val - (data_ + field_offset)));
      return true;
    }
  
    uint8_t *GetAddressOf(voffset_t field) {
      auto field_offset = GetOptionalFieldOffset(field);
      return field_offset ? data_ + field_offset : nullptr;
    }
    const uint8_t *GetAddressOf(voffset_t field) const {
      return const_cast<Table *>(this)->GetAddressOf(field);
    }
  
    bool CheckField(voffset_t field) const {
      return GetOptionalFieldOffset(field) != 0;
    }
  
    // Verify the vtable of this table.
    // Call this once per table, followed by VerifyField once per field.
    bool VerifyTableStart(Verifier &verifier) const {
      // Check the vtable offset.
      if (!verifier.Verify<soffset_t>(data_)) return false;
      auto vtable = GetVTable();
      // Check the vtable size field, then check vtable fits in its entirety.
      return verifier.VerifyComplexity() && verifier.Verify<voffset_t>(vtable) &&
             (ReadScalar<voffset_t>(vtable) & (sizeof(voffset_t) - 1)) == 0 &&
             verifier.Verify(vtable, ReadScalar<voffset_t>(vtable));
    }
  
    // Verify a particular field.
    template<typename T>
    bool VerifyField(const Verifier &verifier, voffset_t field) const {
      // Calling GetOptionalFieldOffset should be safe now thanks to
      // VerifyTable().
      auto field_offset = GetOptionalFieldOffset(field);
      // Check the actual field.
      return !field_offset || verifier.Verify<T>(data_ + field_offset);
    }
  
    // VerifyField for required fields.
    template<typename T>
    bool VerifyFieldRequired(const Verifier &verifier, voffset_t field) const {
      auto field_offset = GetOptionalFieldOffset(field);
      return verifier.Check(field_offset != 0) &&
             verifier.Verify<T>(data_ + field_offset);
    }
  
    // Versions for offsets.
    bool VerifyOffset(const Verifier &verifier, voffset_t field) const {
      auto field_offset = GetOptionalFieldOffset(field);
      return !field_offset || verifier.VerifyOffset(data_ + field_offset);
    }
  
    bool VerifyOffsetRequired(const Verifier &verifier, voffset_t field) const {
      auto field_offset = GetOptionalFieldOffset(field);
      return verifier.Check(field_offset != 0) &&
             verifier.VerifyOffset(data_ + field_offset);
    }
  
   private:
    // private constructor & copy constructor: you obtain instances of this
    // class by pointing to existing data only
    Table();
    Table(const Table &other);
  
    uint8_t data_[1];
  };
  
  /// @brief This can compute the start of a FlatBuffer from a root pointer, i.e.
  /// it is the opposite transformation of GetRoot().
  /// This may be useful if you want to pass on a root and have the recipient
  /// delete the buffer afterwards.
  inline const uint8_t *GetBufferStartFromRootPointer(const void *root) {
    auto table = reinterpret_cast<const Table *>(root);
    auto vtable = table->GetVTable();
    // Either the vtable is before the root or after the root.
    auto start = (std::min)(vtable, reinterpret_cast<const uint8_t *>(root));
    // Align to at least sizeof(uoffset_t).
    start = reinterpret_cast<const uint8_t *>(reinterpret_cast<uintptr_t>(start) &
                                              ~(sizeof(uoffset_t) - 1));
    // Additionally, there may be a file_identifier in the buffer, and the root
    // offset. The buffer may have been aligned to any size between
    // sizeof(uoffset_t) and FLATBUFFERS_MAX_ALIGNMENT (see "force_align").
    // Sadly, the exact alignment is only known when constructing the buffer,
    // since it depends on the presence of values with said alignment properties.
    // So instead, we simply look at the next uoffset_t values (root,
    // file_identifier, and alignment padding) to see which points to the root.
    // None of the other values can "impersonate" the root since they will either
    // be 0 or four ASCII characters.
    static_assert(FlatBufferBuilder::kFileIdentifierLength == sizeof(uoffset_t),
                  "file_identifier is assumed to be the same size as uoffset_t");
    for (auto possible_roots = FLATBUFFERS_MAX_ALIGNMENT / sizeof(uoffset_t) + 1;
         possible_roots; possible_roots--) {
      start -= sizeof(uoffset_t);
      if (ReadScalar<uoffset_t>(start) + start ==
          reinterpret_cast<const uint8_t *>(root))
        return start;
    }
    // We didn't find the root, either the "root" passed isn't really a root,
    // or the buffer is corrupt.
    // Assert, because calling this function with bad data may cause reads
    // outside of buffer boundaries.
    assert(false);
    return nullptr;
  }
  
  // Base class for native objects (FlatBuffer data de-serialized into native
  // C++ data structures).
  // Contains no functionality, purely documentative.
  struct NativeTable {};
  
  /// @brief Function types to be used with resolving hashes into objects and
  /// back again. The resolver gets a pointer to a field inside an object API
  /// object that is of the type specified in the schema using the attribute
  /// `cpp_type` (it is thus important whatever you write to this address
  /// matches that type). The value of this field is initially null, so you
  /// may choose to implement a delayed binding lookup using this function
  /// if you wish. The resolver does the opposite lookup, for when the object
  /// is being serialized again.
  typedef uint64_t hash_value_t;
  // clang-format off
  #ifdef FLATBUFFERS_CPP98_STL
    typedef void (*resolver_function_t)(void **pointer_adr, hash_value_t hash);
    typedef hash_value_t (*rehasher_function_t)(void *pointer);
  #else
    typedef std::function<void (void **pointer_adr, hash_value_t hash)>
            resolver_function_t;
    typedef std::function<hash_value_t (void *pointer)> rehasher_function_t;
  #endif
  // clang-format on
  
  // Helper function to test if a field is present, using any of the field
  // enums in the generated code.
  // `table` must be a generated table type. Since this is a template parameter,
  // this is not typechecked to be a subclass of Table, so beware!
  // Note: this function will return false for fields equal to the default
  // value, since they're not stored in the buffer (unless force_defaults was
  // used).
  template<typename T> bool IsFieldPresent(const T *table, voffset_t field) {
    // Cast, since Table is a private baseclass of any table types.
    return reinterpret_cast<const Table *>(table)->CheckField(field);
  }
  
  // Utility function for reverse lookups on the EnumNames*() functions
  // (in the generated C++ code)
  // names must be NULL terminated.
  inline int LookupEnum(const char **names, const char *name) {
    for (const char **p = names; *p; p++)
      if (!strcmp(*p, name)) return static_cast<int>(p - names);
    return -1;
  }
  
  // These macros allow us to layout a struct with a guarantee that they'll end
  // up looking the same on different compilers and platforms.
  // It does this by disallowing the compiler to do any padding, and then
  // does padding itself by inserting extra padding fields that make every
  // element aligned to its own size.
  // Additionally, it manually sets the alignment of the struct as a whole,
  // which is typically its largest element, or a custom size set in the schema
  // by the force_align attribute.
  // These are used in the generated code only.
  
  // clang-format off
  #if defined(_MSC_VER)
    #define MANUALLY_ALIGNED_STRUCT(alignment) \
      __pragma(pack(1)); \
      struct __declspec(align(alignment))
    #define STRUCT_END(name, size) \
      __pragma(pack()); \
      static_assert(sizeof(name) == size, "compiler breaks packing rules")
  #elif defined(__GNUC__) || defined(__clang__)
    #define MANUALLY_ALIGNED_STRUCT(alignment) \
      _Pragma("pack(1)") \
      struct __attribute__((aligned(alignment)))
    #define STRUCT_END(name, size) \
      _Pragma("pack()") \
      static_assert(sizeof(name) == size, "compiler breaks packing rules")
  #else
    #error Unknown compiler, please define structure alignment macros
  #endif
  // clang-format on
  
  // Minimal reflection via code generation.
  // Besides full-fat reflection (see reflection.h) and parsing/printing by
  // loading schemas (see idl.h), we can also have code generation for mimimal
  // reflection data which allows pretty-printing and other uses without needing
  // a schema or a parser.
  // Generate code with --reflect-types (types only) or --reflect-names (names
  // also) to enable.
  // See minireflect.h for utilities using this functionality.
  
  // These types are organized slightly differently as the ones in idl.h.
  enum SequenceType { ST_TABLE, ST_STRUCT, ST_UNION, ST_ENUM };
  
  // Scalars have the same order as in idl.h
  // clang-format off
  #define FLATBUFFERS_GEN_ELEMENTARY_TYPES(ET) \
    ET(ET_UTYPE) \
    ET(ET_BOOL) \
    ET(ET_CHAR) \
    ET(ET_UCHAR) \
    ET(ET_SHORT) \
    ET(ET_USHORT) \
    ET(ET_INT) \
    ET(ET_UINT) \
    ET(ET_LONG) \
    ET(ET_ULONG) \
    ET(ET_FLOAT) \
    ET(ET_DOUBLE) \
    ET(ET_STRING) \
    ET(ET_SEQUENCE)  // See SequenceType.
  
  enum ElementaryType {
    #define FLATBUFFERS_ET(E) E,
      FLATBUFFERS_GEN_ELEMENTARY_TYPES(FLATBUFFERS_ET)
    #undef FLATBUFFERS_ET
  };
  
  inline const char **ElementaryTypeNames() {
    static const char *names[] = {
      #define FLATBUFFERS_ET(E) #E,
        FLATBUFFERS_GEN_ELEMENTARY_TYPES(FLATBUFFERS_ET)
      #undef FLATBUFFERS_ET
    };
    return names;
  }
  // clang-format on
  
  // Basic type info cost just 16bits per field!
  struct TypeCode {
    uint16_t base_type : 4;  // ElementaryType
    uint16_t is_vector : 1;
    int16_t sequence_ref : 11;  // Index into type_refs below, or -1 for none.
  };
  
  static_assert(sizeof(TypeCode) == 2, "TypeCode");
  
  struct TypeTable;
  
  // Signature of the static method present in each type.
  typedef TypeTable *(*TypeFunction)();
  
  struct TypeTable {
    SequenceType st;
    size_t num_elems;  // of each of the arrays below.
    const TypeCode *type_codes;
    const TypeFunction *type_refs;
    const int32_t *values;  // Only set for non-consecutive enum/union or structs.
    const char **names;     // Only set if compiled with --reflect-names.
  };
  
  // String which identifies the current version of FlatBuffers.
  // flatbuffer_version_string is used by Google developers to identify which
  // applications uploaded to Google Play are using this library.  This allows
  // the development team at Google to determine the popularity of the library.
  // How it works: Applications that are uploaded to the Google Play Store are
  // scanned for this version string.  We track which applications are using it
  // to measure popularity.  You are free to remove it (of course) but we would
  // appreciate if you left it in.
  
  // Weak linkage is culled by VS & doesn't work on cygwin.
  // clang-format off
  #if !defined(_WIN32) && !defined(__CYGWIN__)
  
  extern volatile __attribute__((weak)) const char *flatbuffer_version_string;
  volatile __attribute__((weak)) const char *flatbuffer_version_string =
    "FlatBuffers "
    FLATBUFFERS_STRING(FLATBUFFERS_VERSION_MAJOR) "."
    FLATBUFFERS_STRING(FLATBUFFERS_VERSION_MINOR) "."
    FLATBUFFERS_STRING(FLATBUFFERS_VERSION_REVISION);
  
  #endif  // !defined(_WIN32) && !defined(__CYGWIN__)
  
  #define DEFINE_BITMASK_OPERATORS(E, T)\
      inline E operator | (E lhs, E rhs){\
          return E(T(lhs) | T(rhs));\
      }\
      inline E operator & (E lhs, E rhs){\
          return E(T(lhs) & T(rhs));\
      }\
      inline E operator ^ (E lhs, E rhs){\
          return E(T(lhs) ^ T(rhs));\
      }\
      inline E operator ~ (E lhs){\
          return E(~T(lhs));\
      }\
      inline E operator |= (E &lhs, E rhs){\
          lhs = lhs | rhs;\
          return lhs;\
      }\
      inline E operator &= (E &lhs, E rhs){\
          lhs = lhs & rhs;\
          return lhs;\
      }\
      inline E operator ^= (E &lhs, E rhs){\
          lhs = lhs ^ rhs;\
          return lhs;\
      }\
      inline bool operator !(E rhs) \
      {\
          return !bool(T(rhs)); \
      }
  /// @endcond
  }  // namespace flatbuffers
  
  #if defined(_MSC_VER)
    #pragma warning(pop)
  #endif
  // clang-format on
  
  #endif  // FLATBUFFERS_H_
  