[C++] Split flatbuffers.h into separate files (#6868)

* split flatbuffers.h into separate files

* wrong variable in cmakelists for android

* readded two accidentally deleted includes

* created buffer.h and moved buffer related things over

BUILD.bazel

@@ -37,8 +37,15 @@ cc_library(
 filegroup(
     name = "public_headers",
     srcs = [
+        "include/flatbuffers/allocator.h",
+        "include/flatbuffers/array.h",
         "include/flatbuffers/base.h",
+        "include/flatbuffers/buffer.h",
+        "include/flatbuffers/buffer_ref.h",
         "include/flatbuffers/code_generators.h",
+        "include/flatbuffers/default_allocator.h",
+        "include/flatbuffers/detached_buffer.h",
+        "include/flatbuffers/flatbuffer_builder.h",
         "include/flatbuffers/flatbuffers.h",
         "include/flatbuffers/flexbuffers.h",
         "include/flatbuffers/grpc.h",
@@ -49,7 +56,13 @@ filegroup(
         "include/flatbuffers/reflection_generated.h",
         "include/flatbuffers/registry.h",
         "include/flatbuffers/stl_emulation.h",
+        "include/flatbuffers/string.h",
+        "include/flatbuffers/struct.h",
+        "include/flatbuffers/table.h",
         "include/flatbuffers/util.h",
+        "include/flatbuffers/vector.h",
+        "include/flatbuffers/vector_downward.h",
+        "include/flatbuffers/verifier.h",
     ],
 )
 
@@ -87,6 +100,8 @@ cc_library(
         "include/flatbuffers/flexbuffers.h",
         "include/flatbuffers/stl_emulation.h",
         "include/flatbuffers/util.h",
+        "include/flatbuffers/vector.h",
+        "include/flatbuffers/verifier.h",
     ],
     linkstatic = 1,
     strip_include_prefix = "/include",

CMakeLists.txt

@@ -73,17 +73,30 @@ endif()
 add_definitions(-DFLATBUFFERS_LOCALE_INDEPENDENT=$<BOOL:${FLATBUFFERS_LOCALE_INDEPENDENT}>)
 
 set(FlatBuffers_Library_SRCS
+  include/flatbuffers/allocator.h
+  include/flatbuffers/array.h
   include/flatbuffers/base.h
+  include/flatbuffers/buffer.h
+  include/flatbuffers/buffer_ref.h
+  include/flatbuffers/default_allocator.h
+  include/flatbuffers/detached_buffer.h
+  include/flatbuffers/flatbuffer_builder.h
   include/flatbuffers/flatbuffers.h
+  include/flatbuffers/flexbuffers.h
   include/flatbuffers/hash.h
   include/flatbuffers/idl.h
-  include/flatbuffers/util.h
+  include/flatbuffers/minireflect.h
   include/flatbuffers/reflection.h
   include/flatbuffers/reflection_generated.h
-  include/flatbuffers/stl_emulation.h
-  include/flatbuffers/flexbuffers.h
   include/flatbuffers/registry.h
-  include/flatbuffers/minireflect.h
+  include/flatbuffers/stl_emulation.h
+  include/flatbuffers/string.h
+  include/flatbuffers/struct.h
+  include/flatbuffers/table.h
+  include/flatbuffers/util.h
+  include/flatbuffers/vector.h
+  include/flatbuffers/vector_downward.h
+  include/flatbuffers/verifier.h
   src/idl_parser.cpp
   src/idl_gen_text.cpp
   src/reflection.cpp

android/app/src/main/cpp/flatbuffers/CMakeLists.txt

@@ -15,17 +15,30 @@ set(CMAKE_CXX_FLAGS
    "${CMAKE_CXX_FLAGS} -fsigned-char")
 
 set(FlatBuffers_Library_SRCS
+        ${FLATBUFFERS_SRC}/include/flatbuffers/allocator.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/array.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/base.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/buffer.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/buffer_ref.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/default_allocator.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/detached_buffer.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/flatbuffer_builder.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/flatbuffers.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/flexbuffers.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/hash.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/idl.h
-        ${FLATBUFFERS_SRC}/include/flatbuffers/util.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/minireflect.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/reflection.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/reflection_generated.h
-        ${FLATBUFFERS_SRC}/include/flatbuffers/stl_emulation.h
-        ${FLATBUFFERS_SRC}/include/flatbuffers/flexbuffers.h
         ${FLATBUFFERS_SRC}/include/flatbuffers/registry.h
-        ${FLATBUFFERS_SRC}/include/flatbuffers/minireflect.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/stl_emulation.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/string.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/struct.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/table.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/util.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/vector.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/vector_downward.h
+        ${FLATBUFFERS_SRC}/include/flatbuffers/verifier.h
         ${FLATBUFFERS_SRC}/src/idl_parser.cpp
         ${FLATBUFFERS_SRC}/src/idl_gen_text.cpp
         ${FLATBUFFERS_SRC}/src/reflection.cpp

include/flatbuffers/allocator.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2021 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_ALLOCATOR_H_
+#define FLATBUFFERS_ALLOCATOR_H_
+
+#include "flatbuffers/base.h"
+
+namespace flatbuffers {
+
+// 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.
+  // `in_use_back` and `in_use_front` indicate how much of `old_size` is
+  // actually in use at each end, and needs to be copied.
+  virtual uint8_t *reallocate_downward(uint8_t *old_p, size_t old_size,
+                                       size_t new_size, size_t in_use_back,
+                                       size_t in_use_front) {
+    FLATBUFFERS_ASSERT(new_size > old_size);  // vector_downward only grows
+    uint8_t *new_p = allocate(new_size);
+    memcpy_downward(old_p, old_size, new_p, new_size, in_use_back,
+                    in_use_front);
+    deallocate(old_p, old_size);
+    return new_p;
+  }
+
+ protected:
+  // Called by `reallocate_downward` to copy memory from `old_p` of `old_size`
+  // to `new_p` of `new_size`. Only memory of size `in_use_front` and
+  // `in_use_back` will be copied from the front and back of the old memory
+  // allocation.
+  void memcpy_downward(uint8_t *old_p, size_t old_size, uint8_t *new_p,
+                       size_t new_size, size_t in_use_back,
+                       size_t in_use_front) {
+    memcpy(new_p + new_size - in_use_back, old_p + old_size - in_use_back,
+           in_use_back);
+    memcpy(new_p, old_p, in_use_front);
+  }
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_ALLOCATOR_H_

include/flatbuffers/array.h

@@ -0,0 +1,243 @@
+/*
+ * Copyright 2021 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_ARRAY_H_
+#define FLATBUFFERS_ARRAY_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/stl_emulation.h"
+#include "flatbuffers/vector.h"
+
+namespace flatbuffers {
+
+// This is used as a helper type for accessing arrays.
+template<typename T, uint16_t length> class Array {
+  // Array<T> can carry only POD data types (scalars or structs).
+  typedef typename flatbuffers::bool_constant<flatbuffers::is_scalar<T>::value>
+      scalar_tag;
+  typedef
+      typename flatbuffers::conditional<scalar_tag::value, T, const T *>::type
+          IndirectHelperType;
+
+ public:
+  typedef uint16_t size_type;
+  typedef typename IndirectHelper<IndirectHelperType>::return_type return_type;
+  typedef VectorIterator<T, return_type> const_iterator;
+  typedef VectorReverseIterator<const_iterator> const_reverse_iterator;
+
+  // If T is a LE-scalar or a struct (!scalar_tag::value).
+  static FLATBUFFERS_CONSTEXPR bool is_span_observable =
+      (scalar_tag::value && (FLATBUFFERS_LITTLEENDIAN || sizeof(T) == 1)) ||
+      !scalar_tag::value;
+
+  FLATBUFFERS_CONSTEXPR uint16_t size() const { return length; }
+
+  return_type Get(uoffset_t i) const {
+    FLATBUFFERS_ASSERT(i < size());
+    return IndirectHelper<IndirectHelperType>::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));
+  }
+
+  const_iterator begin() const { return const_iterator(Data(), 0); }
+  const_iterator end() const { return const_iterator(Data(), size()); }
+
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
+  const_iterator cbegin() const { return begin(); }
+  const_iterator cend() const { return end(); }
+
+  const_reverse_iterator crbegin() const { return rbegin(); }
+  const_reverse_iterator crend() const { return rend(); }
+
+  // Get a mutable pointer to elements inside this array.
+  // This method used to mutate arrays of structs followed by a @p Mutate
+  // operation. For primitive types use @p Mutate directly.
+  // @warning Assignments and reads to/from the dereferenced pointer are not
+  //  automatically converted to the correct endianness.
+  typename flatbuffers::conditional<scalar_tag::value, void, T *>::type
+  GetMutablePointer(uoffset_t i) const {
+    FLATBUFFERS_ASSERT(i < size());
+    return const_cast<T *>(&data()[i]);
+  }
+
+  // Change elements if you have a non-const pointer to this object.
+  void Mutate(uoffset_t i, const T &val) { MutateImpl(scalar_tag(), i, val); }
+
+  // The raw data in little endian format. Use with care.
+  const uint8_t *Data() const { return data_; }
+
+  uint8_t *Data() { return data_; }
+
+  // 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()); }
+
+  // Copy data from a span with endian conversion.
+  // If this Array and the span overlap, the behavior is undefined.
+  void CopyFromSpan(flatbuffers::span<const T, length> src) {
+    const auto p1 = reinterpret_cast<const uint8_t *>(src.data());
+    const auto p2 = Data();
+    FLATBUFFERS_ASSERT(!(p1 >= p2 && p1 < (p2 + length)) &&
+                       !(p2 >= p1 && p2 < (p1 + length)));
+    (void)p1;
+    (void)p2;
+    CopyFromSpanImpl(flatbuffers::bool_constant<is_span_observable>(), src);
+  }
+
+ protected:
+  void MutateImpl(flatbuffers::true_type, uoffset_t i, const T &val) {
+    FLATBUFFERS_ASSERT(i < size());
+    WriteScalar(data() + i, val);
+  }
+
+  void MutateImpl(flatbuffers::false_type, uoffset_t i, const T &val) {
+    *(GetMutablePointer(i)) = val;
+  }
+
+  void CopyFromSpanImpl(flatbuffers::true_type,
+                        flatbuffers::span<const T, length> src) {
+    // Use std::memcpy() instead of std::copy() to avoid performance degradation
+    // due to aliasing if T is char or unsigned char.
+    // The size is known at compile time, so memcpy would be inlined.
+    std::memcpy(data(), src.data(), length * sizeof(T));
+  }
+
+  // Copy data from flatbuffers::span with endian conversion.
+  void CopyFromSpanImpl(flatbuffers::false_type,
+                        flatbuffers::span<const T, length> src) {
+    for (size_type k = 0; k < length; k++) { Mutate(k, src[k]); }
+  }
+
+  // This class is only used to access pre-existing data. Don't ever
+  // try to construct these manually.
+  // 'constexpr' allows us to use 'size()' at compile time.
+  // @note Must not use 'FLATBUFFERS_CONSTEXPR' here, as const is not allowed on
+  //  a constructor.
+#if defined(__cpp_constexpr)
+  constexpr Array();
+#else
+  Array();
+#endif
+
+  uint8_t data_[length * sizeof(T)];
+
+ private:
+  // This class is a pointer. Copying will therefore create an invalid object.
+  // Private and unimplemented copy constructor.
+  Array(const Array &);
+  Array &operator=(const Array &);
+};
+
+// Specialization for Array[struct] with access using Offset<void> pointer.
+// This specialization used by idl_gen_text.cpp.
+template<typename T, uint16_t length> class Array<Offset<T>, length> {
+  static_assert(flatbuffers::is_same<T, void>::value, "unexpected type T");
+
+ public:
+  typedef const void *return_type;
+
+  const uint8_t *Data() const { return data_; }
+
+  // Make idl_gen_text.cpp::PrintContainer happy.
+  return_type operator[](uoffset_t) const {
+    FLATBUFFERS_ASSERT(false);
+    return nullptr;
+  }
+
+ private:
+  // This class is only used to access pre-existing data.
+  Array();
+  Array(const Array &);
+  Array &operator=(const Array &);
+
+  uint8_t data_[1];
+};
+
+template<class U, uint16_t N>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<U, N> make_span(Array<U, N> &arr)
+    FLATBUFFERS_NOEXCEPT {
+  static_assert(
+      Array<U, N>::is_span_observable,
+      "wrong type U, only plain struct, LE-scalar, or byte types are allowed");
+  return span<U, N>(arr.data(), N);
+}
+
+template<class U, uint16_t N>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<const U, N> make_span(
+    const Array<U, N> &arr) FLATBUFFERS_NOEXCEPT {
+  static_assert(
+      Array<U, N>::is_span_observable,
+      "wrong type U, only plain struct, LE-scalar, or byte types are allowed");
+  return span<const U, N>(arr.data(), N);
+}
+
+template<class U, uint16_t N>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<uint8_t, sizeof(U) * N>
+make_bytes_span(Array<U, N> &arr) FLATBUFFERS_NOEXCEPT {
+  static_assert(Array<U, N>::is_span_observable,
+                "internal error, Array<T> might hold only scalars or structs");
+  return span<uint8_t, sizeof(U) * N>(arr.Data(), sizeof(U) * N);
+}
+
+template<class U, uint16_t N>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<const uint8_t, sizeof(U) * N>
+make_bytes_span(const Array<U, N> &arr) FLATBUFFERS_NOEXCEPT {
+  static_assert(Array<U, N>::is_span_observable,
+                "internal error, Array<T> might hold only scalars or structs");
+  return span<const uint8_t, sizeof(U) * N>(arr.Data(), sizeof(U) * N);
+}
+
+// Cast a raw T[length] to a raw flatbuffers::Array<T, length>
+// without endian conversion. Use with care.
+// TODO: move these Cast-methods to `internal` namespace.
+template<typename T, uint16_t length>
+Array<T, length> &CastToArray(T (&arr)[length]) {
+  return *reinterpret_cast<Array<T, length> *>(arr);
+}
+
+template<typename T, uint16_t length>
+const Array<T, length> &CastToArray(const T (&arr)[length]) {
+  return *reinterpret_cast<const Array<T, length> *>(arr);
+}
+
+template<typename E, typename T, uint16_t length>
+Array<E, length> &CastToArrayOfEnum(T (&arr)[length]) {
+  static_assert(sizeof(E) == sizeof(T), "invalid enum type E");
+  return *reinterpret_cast<Array<E, length> *>(arr);
+}
+
+template<typename E, typename T, uint16_t length>
+const Array<E, length> &CastToArrayOfEnum(const T (&arr)[length]) {
+  static_assert(sizeof(E) == sizeof(T), "invalid enum type E");
+  return *reinterpret_cast<const Array<E, length> *>(arr);
+}
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_ARRAY_H_

include/flatbuffers/base.h

@@ -335,6 +335,9 @@ typedef uintmax_t largest_scalar_t;
 // We support aligning the contents of buffers up to this size.
 #define FLATBUFFERS_MAX_ALIGNMENT 16
 
+/// @brief The length of a FlatBuffer file header.
+static const size_t kFileIdentifierLength = 4;
+
 inline bool VerifyAlignmentRequirements(size_t align, size_t min_align = 1) {
   return (min_align <= align) && (align <= (FLATBUFFERS_MAX_ALIGNMENT)) &&
          (align & (align - 1)) == 0;  // must be power of 2
@@ -438,5 +441,38 @@ inline size_t PaddingBytes(size_t buf_size, size_t scalar_size) {
   return ((~buf_size) + 1) & (scalar_size - 1);
 }
 
+// Generic 'operator==' with conditional specialisations.
+// T e - new value of a scalar field.
+// T def - default of scalar (is known at compile-time).
+template<typename T> inline bool IsTheSameAs(T e, T def) { return e == def; }
+
+#if defined(FLATBUFFERS_NAN_DEFAULTS) && \
+    defined(FLATBUFFERS_HAS_NEW_STRTOD) && (FLATBUFFERS_HAS_NEW_STRTOD > 0)
+// Like `operator==(e, def)` with weak NaN if T=(float|double).
+template<typename T> inline bool IsFloatTheSameAs(T e, T def) {
+  return (e == def) || ((def != def) && (e != e));
+}
+template<> inline bool IsTheSameAs<float>(float e, float def) {
+  return IsFloatTheSameAs(e, def);
+}
+template<> inline bool IsTheSameAs<double>(double e, double def) {
+  return IsFloatTheSameAs(e, def);
+}
+#endif
+
+// Check 'v' is out of closed range [low; high].
+// Workaround for GCC warning [-Werror=type-limits]:
+// comparison is always true due to limited range of data type.
+template<typename T>
+inline bool IsOutRange(const T &v, const T &low, const T &high) {
+  return (v < low) || (high < v);
+}
+
+// Check 'v' is in closed range [low; high].
+template<typename T>
+inline bool IsInRange(const T &v, const T &low, const T &high) {
+  return !IsOutRange(v, low, high);
+}
+
 }  // namespace flatbuffers
 #endif  // FLATBUFFERS_BASE_H_

include/flatbuffers/buffer.h

@@ -0,0 +1,142 @@
+/*
+ * Copyright 2021 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_BUFFER_H_
+#define FLATBUFFERS_BUFFER_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.
+  FLATBUFFERS_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
+}
+
+// Lexicographically compare two strings (possibly containing nulls), and
+// return true if the first is less than the second.
+static inline bool StringLessThan(const char *a_data, uoffset_t a_size,
+                                  const char *b_data, uoffset_t b_size) {
+  const auto cmp = memcmp(a_data, b_data, (std::min)(a_size, b_size));
+  return cmp == 0 ? a_size < b_size : cmp < 0;
+}
+
+// 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));
+  }
+};
+
+/// @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,
+                                       bool size_prefixed = false) {
+  return reinterpret_cast<const char *>(buf) +
+         ((size_prefixed) ? 2 * sizeof(uoffset_t) : 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,
+                                bool size_prefixed = false) {
+  return strncmp(GetBufferIdentifier(buf, size_prefixed), identifier,
+                 flatbuffers::kFileIdentifierLength) == 0;
+}
+
+/// @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> T *GetMutableSizePrefixedRoot(void *buf) {
+  return GetMutableRoot<T>(reinterpret_cast<uint8_t *>(buf) +
+                           sizeof(uoffset_t));
+}
+
+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));
+}
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_BUFFER_H_

include/flatbuffers/buffer_ref.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2021 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_BUFFER_REF_H_
+#define FLATBUFFERS_BUFFER_REF_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/verifier.h"
+
+namespace flatbuffers {
+
+// 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;
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_BUFFER_REF_H_

include/flatbuffers/default_allocator.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2021 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_DEFAULT_ALLOCATOR_H_
+#define FLATBUFFERS_DEFAULT_ALLOCATOR_H_
+
+#include "flatbuffers/allocator.h"
+#include "flatbuffers/base.h"
+
+namespace flatbuffers {
+
+// DefaultAllocator uses new/delete to allocate memory regions
+class DefaultAllocator : public Allocator {
+ public:
+  uint8_t *allocate(size_t size) FLATBUFFERS_OVERRIDE {
+    return new uint8_t[size];
+  }
+
+  void deallocate(uint8_t *p, size_t) FLATBUFFERS_OVERRIDE { delete[] p; }
+
+  static void dealloc(void *p, size_t) { delete[] static_cast<uint8_t *>(p); }
+};
+
+// These functions allow for a null allocator to mean use the default allocator,
+// as used by DetachedBuffer and vector_downward below.
+// This is to avoid having a statically or dynamically allocated default
+// allocator, or having to move it between the classes that may own it.
+inline uint8_t *Allocate(Allocator *allocator, size_t size) {
+  return allocator ? allocator->allocate(size)
+                   : DefaultAllocator().allocate(size);
+}
+
+inline void Deallocate(Allocator *allocator, uint8_t *p, size_t size) {
+  if (allocator)
+    allocator->deallocate(p, size);
+  else
+    DefaultAllocator().deallocate(p, size);
+}
+
+inline uint8_t *ReallocateDownward(Allocator *allocator, uint8_t *old_p,
+                                   size_t old_size, size_t new_size,
+                                   size_t in_use_back, size_t in_use_front) {
+  return allocator ? allocator->reallocate_downward(old_p, old_size, new_size,
+                                                    in_use_back, in_use_front)
+                   : DefaultAllocator().reallocate_downward(
+                         old_p, old_size, new_size, in_use_back, in_use_front);
+}
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_DEFAULT_ALLOCATOR_H_

include/flatbuffers/detached_buffer.h

@@ -0,0 +1,132 @@
+/*
+ * Copyright 2021 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_DETACHED_BUFFER_H_
+#define FLATBUFFERS_DETACHED_BUFFER_H_
+
+#include "flatbuffers/allocator.h"
+#include "flatbuffers/base.h"
+#include "flatbuffers/default_allocator.h"
+
+namespace flatbuffers {
+
+// 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) {}
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+  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();
+  }
+  // clang-format off
+  #endif  // !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+  DetachedBuffer &operator=(DetachedBuffer &&other) {
+    if (this == &other) return *this;
+
+    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;
+  }
+  // clang-format off
+  #endif  // !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+
+  ~DetachedBuffer() { destroy(); }
+
+  const uint8_t *data() const { return cur_; }
+
+  uint8_t *data() { return cur_; }
+
+  size_t size() const { return size_; }
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  // 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));
+  // clang-format off
+  #endif  // !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+
+ protected:
+  Allocator *allocator_;
+  bool own_allocator_;
+  uint8_t *buf_;
+  size_t reserved_;
+  uint8_t *cur_;
+  size_t size_;
+
+  inline void destroy() {
+    if (buf_) Deallocate(allocator_, 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;
+  }
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_DETACHED_BUFFER_H_

include/flatbuffers/registry.h

@@ -17,6 +17,7 @@
 #ifndef FLATBUFFERS_REGISTRY_H_
 #define FLATBUFFERS_REGISTRY_H_
 
+#include "flatbuffers/base.h"
 #include "flatbuffers/idl.h"
 
 namespace flatbuffers {
@@ -40,13 +41,13 @@ class Registry {
   bool FlatBufferToText(const uint8_t *flatbuf, size_t len, std::string *dest) {
     // Get the identifier out of the buffer.
     // If the buffer is truncated, exit.
-    if (len < sizeof(uoffset_t) + FlatBufferBuilder::kFileIdentifierLength) {
+    if (len < sizeof(uoffset_t) + kFileIdentifierLength) {
       lasterror_ = "buffer truncated";
       return false;
     }
     std::string ident(
         reinterpret_cast<const char *>(flatbuf) + sizeof(uoffset_t),
-        FlatBufferBuilder::kFileIdentifierLength);
+        kFileIdentifierLength);
     // Load and parse the schema.
     Parser parser;
     if (!LoadSchema(ident, &parser)) return false;

include/flatbuffers/string.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2021 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_STRING_H_
+#define FLATBUFFERS_STRING_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/vector.h"
+
+namespace flatbuffers {
+
+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(), size()); }
+
+  // clang-format off
+  #ifdef FLATBUFFERS_HAS_STRING_VIEW
+  flatbuffers::string_view string_view() const {
+    return flatbuffers::string_view(c_str(), size());
+  }
+  #endif // FLATBUFFERS_HAS_STRING_VIEW
+  // clang-format on
+
+  bool operator<(const String &o) const {
+    return StringLessThan(this->data(), this->size(), o.data(), o.size());
+  }
+};
+
+// Convenience function to get std::string from a String returning an empty
+// string on null pointer.
+static inline std::string GetString(const String *str) {
+  return str ? str->str() : "";
+}
+
+// Convenience function to get char* from a String returning an empty string on
+// null pointer.
+static inline const char *GetCstring(const String *str) {
+  return str ? str->c_str() : "";
+}
+
+#ifdef FLATBUFFERS_HAS_STRING_VIEW
+// Convenience function to get string_view from a String returning an empty
+// string_view on null pointer.
+static inline flatbuffers::string_view GetStringView(const String *str) {
+  return str ? str->string_view() : flatbuffers::string_view();
+}
+#endif  // FLATBUFFERS_HAS_STRING_VIEW
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_STRING_H_

include/flatbuffers/struct.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2021 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_STRUCT_H_
+#define FLATBUFFERS_STRUCT_H_
+
+#include "flatbuffers/base.h"
+
+namespace flatbuffers {
+
+// "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:
+  // private constructor & copy constructor: you obtain instances of this
+  // class by pointing to existing data only
+  Struct();
+  Struct(const Struct &);
+  Struct &operator=(const Struct &);
+
+  uint8_t data_[1];
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_STRUCT_H_

include/flatbuffers/table.h

@@ -0,0 +1,166 @@
+/*
+ * Copyright 2021 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_TABLE_H_
+#define FLATBUFFERS_TABLE_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/verifier.h"
+
+namespace flatbuffers {
+
+// "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 Raw, typename Face>
+  flatbuffers::Optional<Face> GetOptional(voffset_t field) const {
+    auto field_offset = GetOptionalFieldOffset(field);
+    auto p = data_ + field_offset;
+    return field_offset ? Optional<Face>(static_cast<Face>(ReadScalar<Raw>(p)))
+                        : Optional<Face>();
+  }
+
+  template<typename T> bool SetField(voffset_t field, T val, T def) {
+    auto field_offset = GetOptionalFieldOffset(field);
+    if (!field_offset) return IsTheSameAs(val, def);
+    WriteScalar(data_ + field_offset, val);
+    return true;
+  }
+  template<typename T> bool SetField(voffset_t field, T val) {
+    auto field_offset = GetOptionalFieldOffset(field);
+    if (!field_offset) return false;
+    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 {
+    return verifier.VerifyTableStart(data_);
+  }
+
+  // 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);
+  Table &operator=(const Table &);
+
+  uint8_t data_[1];
+};
+
+// This specialization allows avoiding warnings like:
+// MSVC C4800: type: forcing value to bool 'true' or 'false'.
+template<>
+inline flatbuffers::Optional<bool> Table::GetOptional<uint8_t, bool>(
+    voffset_t field) const {
+  auto field_offset = GetOptionalFieldOffset(field);
+  auto p = data_ + field_offset;
+  return field_offset ? Optional<bool>(ReadScalar<uint8_t>(p) != 0)
+                      : Optional<bool>();
+}
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_TABLE_H_

include/flatbuffers/vector.h

@@ -0,0 +1,376 @@
+/*
+ * Copyright 2021 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_VECTOR_H_
+#define FLATBUFFERS_VECTOR_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/buffer.h"
+
+namespace flatbuffers {
+
+struct String;
+
+// 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 ptrdiff_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() : data_(nullptr) {}
+
+  VectorIterator &operator=(const VectorIterator &other) {
+    data_ = other.data_;
+    return *this;
+  }
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  VectorIterator &operator=(VectorIterator &&other) {
+    data_ = other.data_;
+    return *this;
+  }
+  #endif  // !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+
+  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_;
+  }
+
+  difference_type operator-(const VectorIterator &other) const {
+    return (data_ - other.data_) / IndirectHelper<T>::element_stride;
+  }
+
+  // Note: return type is incompatible with the standard
+  // `reference operator*()`.
+  IT operator*() const { return IndirectHelper<T>::Read(data_, 0); }
+
+  // Note: return type is incompatible with the standard
+  // `pointer operator->()`.
+  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) const {
+    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_;
+};
+
+template<typename Iterator>
+struct VectorReverseIterator : public std::reverse_iterator<Iterator> {
+  explicit VectorReverseIterator(Iterator iter)
+      : std::reverse_iterator<Iterator>(iter) {}
+
+  // Note: return type is incompatible with the standard
+  // `reference operator*()`.
+  typename Iterator::value_type operator*() const {
+    auto tmp = std::reverse_iterator<Iterator>::current;
+    return *--tmp;
+  }
+
+  // Note: return type is incompatible with the standard
+  // `pointer operator->()`.
+  typename Iterator::value_type operator->() const {
+    auto tmp = std::reverse_iterator<Iterator>::current;
+    return *--tmp;
+  }
+};
+
+// 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;
+  typedef VectorReverseIterator<iterator> reverse_iterator;
+  typedef VectorReverseIterator<const_iterator> const_reverse_iterator;
+
+  typedef typename flatbuffers::bool_constant<flatbuffers::is_scalar<T>::value>
+      scalar_tag;
+
+  static FLATBUFFERS_CONSTEXPR bool is_span_observable =
+      scalar_tag::value && (FLATBUFFERS_LITTLEENDIAN || sizeof(T) == 1);
+
+  uoffset_t size() const { return EndianScalar(length_); }
+
+  // Deprecated: use size(). Here for backwards compatibility.
+  FLATBUFFERS_ATTRIBUTE(deprecated("use size() instead"))
+  uoffset_t Length() const { return size(); }
+
+  typedef typename IndirectHelper<T>::return_type return_type;
+  typedef typename IndirectHelper<T>::mutable_return_type mutable_return_type;
+  typedef return_type value_type;
+
+  return_type Get(uoffset_t i) const {
+    FLATBUFFERS_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()); }
+
+  reverse_iterator rbegin() { return reverse_iterator(end()); }
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+
+  reverse_iterator rend() { return reverse_iterator(begin()); }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
+  const_iterator cbegin() const { return begin(); }
+
+  const_iterator cend() const { return end(); }
+
+  const_reverse_iterator crbegin() const { return rbegin(); }
+
+  const_reverse_iterator crend() const { return rend(); }
+
+  // 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) {
+    FLATBUFFERS_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) {
+    FLATBUFFERS_ASSERT(i < size());
+    static_assert(sizeof(T) == sizeof(uoffset_t), "Unrelated types");
+    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 {
+    FLATBUFFERS_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);
+  }
+
+  template<typename K> mutable_return_type MutableLookupByKey(K key) {
+    return const_cast<mutable_return_type>(LookupByKey(key));
+  }
+
+ 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 &);
+  Vector &operator=(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);
+  }
+};
+
+template<class U>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<U> make_span(Vector<U> &vec)
+    FLATBUFFERS_NOEXCEPT {
+  static_assert(Vector<U>::is_span_observable,
+                "wrong type U, only LE-scalar, or byte types are allowed");
+  return span<U>(vec.data(), vec.size());
+}
+
+template<class U>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<const U> make_span(
+    const Vector<U> &vec) FLATBUFFERS_NOEXCEPT {
+  static_assert(Vector<U>::is_span_observable,
+                "wrong type U, only LE-scalar, or byte types are allowed");
+  return span<const U>(vec.data(), vec.size());
+}
+
+template<class U>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<uint8_t> make_bytes_span(
+    Vector<U> &vec) FLATBUFFERS_NOEXCEPT {
+  static_assert(Vector<U>::scalar_tag::value,
+                "wrong type U, only LE-scalar, or byte types are allowed");
+  return span<uint8_t>(vec.Data(), vec.size() * sizeof(U));
+}
+
+template<class U>
+FLATBUFFERS_CONSTEXPR_CPP11 flatbuffers::span<const uint8_t> make_bytes_span(
+    const Vector<U> &vec) FLATBUFFERS_NOEXCEPT {
+  static_assert(Vector<U>::scalar_tag::value,
+                "wrong type U, only LE-scalar, or byte types are allowed");
+  return span<const uint8_t>(vec.Data(), vec.size() * sizeof(U));
+}
+
+// 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 &);
+  VectorOfAny &operator=(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 whether 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->size() : 0;
+}
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_VERIFIER_H_

include/flatbuffers/vector_downward.h

@@ -0,0 +1,272 @@
+/*
+ * Copyright 2021 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_VECTOR_DOWNWARD_H_
+#define FLATBUFFERS_VECTOR_DOWNWARD_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/default_allocator.h"
+#include "flatbuffers/detached_buffer.h"
+
+namespace flatbuffers {
+
+// 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.
+// Since this vector leaves the lower part unused, we support a "scratch-pad"
+// that can be stored there for temporary data, to share the allocated space.
+// Essentially, this supports 2 std::vectors in a single buffer.
+class vector_downward {
+ public:
+  explicit vector_downward(size_t initial_size, Allocator *allocator,
+                           bool own_allocator, size_t buffer_minalign)
+      : allocator_(allocator),
+        own_allocator_(own_allocator),
+        initial_size_(initial_size),
+        buffer_minalign_(buffer_minalign),
+        reserved_(0),
+        buf_(nullptr),
+        cur_(nullptr),
+        scratch_(nullptr) {}
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  vector_downward(vector_downward &&other)
+  #else
+  vector_downward(vector_downward &other)
+  #endif  // defined(FLATBUFFERS_CPP98_STL)
+      // clang-format on
+      : allocator_(other.allocator_),
+        own_allocator_(other.own_allocator_),
+        initial_size_(other.initial_size_),
+        buffer_minalign_(other.buffer_minalign_),
+        reserved_(other.reserved_),
+        buf_(other.buf_),
+        cur_(other.cur_),
+        scratch_(other.scratch_) {
+    // No change in other.allocator_
+    // No change in other.initial_size_
+    // No change in other.buffer_minalign_
+    other.own_allocator_ = false;
+    other.reserved_ = 0;
+    other.buf_ = nullptr;
+    other.cur_ = nullptr;
+    other.scratch_ = nullptr;
+  }
+
+  // clang-format off
+  #if !defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+  vector_downward &operator=(vector_downward &&other) {
+    // Move construct a temporary and swap idiom
+    vector_downward temp(std::move(other));
+    swap(temp);
+    return *this;
+  }
+  // clang-format off
+  #endif  // defined(FLATBUFFERS_CPP98_STL)
+  // clang-format on
+
+  ~vector_downward() {
+    clear_buffer();
+    clear_allocator();
+  }
+
+  void reset() {
+    clear_buffer();
+    clear();
+  }
+
+  void clear() {
+    if (buf_) {
+      cur_ = buf_ + reserved_;
+    } else {
+      reserved_ = 0;
+      cur_ = nullptr;
+    }
+    clear_scratch();
+  }
+
+  void clear_scratch() { scratch_ = buf_; }
+
+  void clear_allocator() {
+    if (own_allocator_ && allocator_) { delete allocator_; }
+    allocator_ = nullptr;
+    own_allocator_ = false;
+  }
+
+  void clear_buffer() {
+    if (buf_) Deallocate(allocator_, buf_, reserved_);
+    buf_ = nullptr;
+  }
+
+  // Relinquish the pointer to the caller.
+  uint8_t *release_raw(size_t &allocated_bytes, size_t &offset) {
+    auto *buf = buf_;
+    allocated_bytes = reserved_;
+    offset = static_cast<size_t>(cur_ - buf_);
+
+    // release_raw only relinquishes the buffer ownership.
+    // Does not deallocate or reset the allocator. Destructor will do that.
+    buf_ = nullptr;
+    clear();
+    return buf;
+  }
+
+  // Relinquish the pointer to the caller.
+  DetachedBuffer release() {
+    // allocator ownership (if any) is transferred to DetachedBuffer.
+    DetachedBuffer fb(allocator_, own_allocator_, buf_, reserved_, cur_,
+                      size());
+    if (own_allocator_) {
+      allocator_ = nullptr;
+      own_allocator_ = false;
+    }
+    buf_ = nullptr;
+    clear();
+    return fb;
+  }
+
+  size_t ensure_space(size_t len) {
+    FLATBUFFERS_ASSERT(cur_ >= scratch_ && scratch_ >= buf_);
+    if (len > static_cast<size_t>(cur_ - scratch_)) { reallocate(len); }
+    // Beyond this, signed offsets may not have enough range:
+    // (FlatBuffers > 2GB not supported).
+    FLATBUFFERS_ASSERT(size() < FLATBUFFERS_MAX_BUFFER_SIZE);
+    return len;
+  }
+
+  inline uint8_t *make_space(size_t len) {
+    size_t space = ensure_space(len);
+    cur_ -= space;
+    return cur_;
+  }
+
+  // Returns nullptr if using the DefaultAllocator.
+  Allocator *get_custom_allocator() { return allocator_; }
+
+  uoffset_t size() const {
+    return static_cast<uoffset_t>(reserved_ - static_cast<size_t>(cur_ - buf_));
+  }
+
+  uoffset_t scratch_size() const {
+    return static_cast<uoffset_t>(scratch_ - buf_);
+  }
+
+  size_t capacity() const { return reserved_; }
+
+  uint8_t *data() const {
+    FLATBUFFERS_ASSERT(cur_);
+    return cur_;
+  }
+
+  uint8_t *scratch_data() const {
+    FLATBUFFERS_ASSERT(buf_);
+    return buf_;
+  }
+
+  uint8_t *scratch_end() const {
+    FLATBUFFERS_ASSERT(scratch_);
+    return scratch_;
+  }
+
+  uint8_t *data_at(size_t offset) const { return buf_ + reserved_ - offset; }
+
+  void push(const uint8_t *bytes, size_t num) {
+    if (num > 0) { memcpy(make_space(num), bytes, num); }
+  }
+
+  // Specialized version of push() that avoids memcpy call for small data.
+  template<typename T> void push_small(const T &little_endian_t) {
+    make_space(sizeof(T));
+    *reinterpret_cast<T *>(cur_) = little_endian_t;
+  }
+
+  template<typename T> void scratch_push_small(const T &t) {
+    ensure_space(sizeof(T));
+    *reinterpret_cast<T *>(scratch_) = t;
+    scratch_ += sizeof(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) {
+    make_space(zero_pad_bytes);
+    for (size_t i = 0; i < zero_pad_bytes; i++) cur_[i] = 0;
+  }
+
+  // Version for when we know the size is larger.
+  // Precondition: zero_pad_bytes > 0
+  void fill_big(size_t zero_pad_bytes) {
+    memset(make_space(zero_pad_bytes), 0, zero_pad_bytes);
+  }
+
+  void pop(size_t bytes_to_remove) { cur_ += bytes_to_remove; }
+  void scratch_pop(size_t bytes_to_remove) { scratch_ -= bytes_to_remove; }
+
+  void swap(vector_downward &other) {
+    using std::swap;
+    swap(allocator_, other.allocator_);
+    swap(own_allocator_, other.own_allocator_);
+    swap(initial_size_, other.initial_size_);
+    swap(buffer_minalign_, other.buffer_minalign_);
+    swap(reserved_, other.reserved_);
+    swap(buf_, other.buf_);
+    swap(cur_, other.cur_);
+    swap(scratch_, other.scratch_);
+  }
+
+  void swap_allocator(vector_downward &other) {
+    using std::swap;
+    swap(allocator_, other.allocator_);
+    swap(own_allocator_, other.own_allocator_);
+  }
+
+ 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 buffer_minalign_;
+  size_t reserved_;
+  uint8_t *buf_;
+  uint8_t *cur_;  // Points at location between empty (below) and used (above).
+  uint8_t *scratch_;  // Points to the end of the scratchpad in use.
+
+  void reallocate(size_t len) {
+    auto old_reserved = reserved_;
+    auto old_size = size();
+    auto old_scratch_size = scratch_size();
+    reserved_ +=
+        (std::max)(len, old_reserved ? old_reserved / 2 : initial_size_);
+    reserved_ = (reserved_ + buffer_minalign_ - 1) & ~(buffer_minalign_ - 1);
+    if (buf_) {
+      buf_ = ReallocateDownward(allocator_, buf_, old_reserved, reserved_,
+                                old_size, old_scratch_size);
+    } else {
+      buf_ = Allocate(allocator_, reserved_);
+    }
+    cur_ = buf_ + reserved_ - old_size;
+    scratch_ = buf_ + old_scratch_size;
+  }
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_VECTOR_DOWNWARD_H_

include/flatbuffers/verifier.h

@@ -0,0 +1,262 @@
+/*
+ * Copyright 2021 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_VERIFIER_H_
+#define FLATBUFFERS_VERIFIER_H_
+
+#include "flatbuffers/base.h"
+#include "flatbuffers/util.h"
+#include "flatbuffers/vector.h"
+
+namespace flatbuffers {
+
+// 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, bool _check_alignment = true)
+      : buf_(buf),
+        size_(buf_len),
+        depth_(0),
+        max_depth_(_max_depth),
+        num_tables_(0),
+        max_tables_(_max_tables),
+        upper_bound_(0),
+        check_alignment_(_check_alignment) {
+    FLATBUFFERS_ASSERT(size_ < FLATBUFFERS_MAX_BUFFER_SIZE);
+  }
+
+  // Central location where any verification failures register.
+  bool Check(bool ok) const {
+    // clang-format off
+    #ifdef FLATBUFFERS_DEBUG_VERIFICATION_FAILURE
+      FLATBUFFERS_ASSERT(ok);
+    #endif
+    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
+      if (!ok)
+        upper_bound_ = 0;
+    #endif
+    // clang-format on
+    return ok;
+  }
+
+  // Verify any range within the buffer.
+  bool Verify(size_t elem, size_t elem_len) const {
+    // clang-format off
+    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
+      auto upper_bound = elem + elem_len;
+      if (upper_bound_ < upper_bound)
+        upper_bound_ =  upper_bound;
+    #endif
+    // clang-format on
+    return Check(elem_len < size_ && elem <= size_ - elem_len);
+  }
+
+  template<typename T> bool VerifyAlignment(size_t elem) const {
+    return Check((elem & (sizeof(T) - 1)) == 0 || !check_alignment_);
+  }
+
+  // Verify a range indicated by sizeof(T).
+  template<typename T> bool Verify(size_t elem) const {
+    return VerifyAlignment<T>(elem) && Verify(elem, sizeof(T));
+  }
+
+  bool VerifyFromPointer(const uint8_t *p, size_t len) {
+    auto o = static_cast<size_t>(p - buf_);
+    return Verify(o, len);
+  }
+
+  // Verify relative to a known-good base pointer.
+  bool Verify(const uint8_t *base, voffset_t elem_off, size_t elem_len) const {
+    return Verify(static_cast<size_t>(base - buf_) + elem_off, elem_len);
+  }
+
+  template<typename T>
+  bool Verify(const uint8_t *base, voffset_t elem_off) const {
+    return Verify(static_cast<size_t>(base - buf_) + elem_off, 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 VerifyVector(const Vector<T> *vec) const {
+    return !vec || VerifyVectorOrString(reinterpret_cast<const uint8_t *>(vec),
+                                        sizeof(T));
+  }
+
+  // Verify a pointer (may be NULL) of a vector to struct.
+  template<typename T> bool VerifyVector(const Vector<const T *> *vec) const {
+    return VerifyVector(reinterpret_cast<const Vector<T> *>(vec));
+  }
+
+  // Verify a pointer (may be NULL) to string.
+  bool VerifyString(const String *str) const {
+    size_t end;
+    return !str || (VerifyVectorOrString(reinterpret_cast<const uint8_t *>(str),
+                                         1, &end) &&
+                    Verify(end, 1) &&           // Must have terminator
+                    Check(buf_[end] == '\0'));  // Terminating byte must be 0.
+  }
+
+  // Common code between vectors and strings.
+  bool VerifyVectorOrString(const uint8_t *vec, size_t elem_size,
+                            size_t *end = nullptr) const {
+    auto veco = static_cast<size_t>(vec - buf_);
+    // Check we can read the size field.
+    if (!Verify<uoffset_t>(veco)) 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;
+    if (end) *end = veco + byte_size;
+    return Verify(veco, 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 (!VerifyString(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;
+  }
+
+  __supress_ubsan__("unsigned-integer-overflow") bool VerifyTableStart(
+      const uint8_t *table) {
+    // Check the vtable offset.
+    auto tableo = static_cast<size_t>(table - buf_);
+    if (!Verify<soffset_t>(tableo)) return false;
+    // This offset may be signed, but doing the subtraction unsigned always
+    // gives the result we want.
+    auto vtableo = tableo - static_cast<size_t>(ReadScalar<soffset_t>(table));
+    // Check the vtable size field, then check vtable fits in its entirety.
+    return VerifyComplexity() && Verify<voffset_t>(vtableo) &&
+           VerifyAlignment<voffset_t>(ReadScalar<voffset_t>(buf_ + vtableo)) &&
+           Verify(vtableo, ReadScalar<voffset_t>(buf_ + vtableo));
+  }
+
+  template<typename T>
+  bool VerifyBufferFromStart(const char *identifier, size_t start) {
+    if (identifier && !Check((size_ >= 2 * sizeof(flatbuffers::uoffset_t) &&
+                              BufferHasIdentifier(buf_ + 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 *>(buf_ + start + o)->Verify(*this)
+    // clang-format off
+    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
+           && GetComputedSize()
+    #endif
+        ;
+    // clang-format on
+  }
+
+  // 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, 0);
+  }
+
+  template<typename T> bool VerifySizePrefixedBuffer(const char *identifier) {
+    return Verify<uoffset_t>(0U) &&
+           ReadScalar<uoffset_t>(buf_) == size_ - sizeof(uoffset_t) &&
+           VerifyBufferFromStart<T>(identifier, sizeof(uoffset_t));
+  }
+
+  uoffset_t VerifyOffset(size_t start) const {
+    if (!Verify<uoffset_t>(start)) return 0;
+    auto o = ReadScalar<uoffset_t>(buf_ + start);
+    // May not point to itself.
+    if (!Check(o != 0)) return 0;
+    // Can't wrap around / buffers are max 2GB.
+    if (!Check(static_cast<soffset_t>(o) >= 0)) return 0;
+    // Must be inside the buffer to create a pointer from it (pointer outside
+    // buffer is UB).
+    if (!Verify(start + o, 1)) return 0;
+    return o;
+  }
+
+  uoffset_t VerifyOffset(const uint8_t *base, voffset_t start) const {
+    return VerifyOffset(static_cast<size_t>(base - buf_) + start);
+  }
+
+  // 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;
+  }
+
+  // Returns the message size in bytes
+  size_t GetComputedSize() const {
+    // clang-format off
+    #ifdef FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
+      uintptr_t size = upper_bound_;
+      // Align the size to uoffset_t
+      size = (size - 1 + sizeof(uoffset_t)) & ~(sizeof(uoffset_t) - 1);
+      return (size > size_) ?  0 : size;
+    #else
+      // Must turn on FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE for this to work.
+      (void)upper_bound_;
+      FLATBUFFERS_ASSERT(false);
+      return 0;
+    #endif
+    // clang-format on
+  }
+
+ private:
+  const uint8_t *buf_;
+  size_t size_;
+  uoffset_t depth_;
+  uoffset_t max_depth_;
+  uoffset_t num_tables_;
+  uoffset_t max_tables_;
+  mutable size_t upper_bound_;
+  bool check_alignment_;
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_VERIFIER_H_

src/idl_parser.cpp

@@ -20,6 +20,7 @@
 #include <string>
 #include <utility>
 
+#include "flatbuffers/base.h"
 #include "flatbuffers/idl.h"
 #include "flatbuffers/util.h"
 
@@ -3404,9 +3405,9 @@ CheckedError Parser::DoParse(const char *source, const char **include_paths,
       NEXT();
       file_identifier_ = attribute_;
       EXPECT(kTokenStringConstant);
-      if (file_identifier_.length() != FlatBufferBuilder::kFileIdentifierLength)
+      if (file_identifier_.length() != flatbuffers::kFileIdentifierLength)
         return Error("file_identifier must be exactly " +
-                     NumToString(FlatBufferBuilder::kFileIdentifierLength) +
+                     NumToString(flatbuffers::kFileIdentifierLength) +
                      " characters");
       EXPECT(';');
     } else if (IsIdent("file_extension")) {

tests/fuzzer/CMakeLists.txt

@@ -85,17 +85,30 @@ target_link_libraries(
 set(FLATBUFFERS_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../")
 
 set(FlatBuffers_Library_SRCS
+    ${FLATBUFFERS_DIR}/include/flatbuffers/allocator.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/array.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/base.h
+    ${FLATBUFFERS_DIR}/include/flatbuffer/buffer.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/buffer_ref.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/default_allocator.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/detached_buffer.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/flatbuffer_builder.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/flatbuffers.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/flexbuffers.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/hash.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/idl.h
-    ${FLATBUFFERS_DIR}/include/flatbuffers/util.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/minireflect.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/reflection.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/reflection_generated.h
-    ${FLATBUFFERS_DIR}/include/flatbuffers/stl_emulation.h
-    ${FLATBUFFERS_DIR}/include/flatbuffers/flexbuffers.h
     ${FLATBUFFERS_DIR}/include/flatbuffers/registry.h
-    ${FLATBUFFERS_DIR}/include/flatbuffers/minireflect.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/stl_emulation.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/string.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/struct.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/table.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/util.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/vector.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/vector_downward.h
+    ${FLATBUFFERS_DIR}/include/flatbuffers/verifier.h
     ${FLATBUFFERS_DIR}/src/idl_parser.cpp
     ${FLATBUFFERS_DIR}/src/idl_gen_text.cpp
     ${FLATBUFFERS_DIR}/src/reflection.cpp