Flatbuffers 的 C++使用示例

怼烎@ 2022-11-03 11:06 403阅读 0赞

## [monster.fbs][] ##

FlatBuffers 使用`.`来指定嵌套的名称空间/包。  
`root_type`声明序列化数据的根表（或结构）。  
除了基本类型外，`Monster`中包含一个表和一个结构体。

表是在 FlatBuffers 中定义对象的主要方式，由名称（此处为`Monster`）和字段列表组成。每个字段都有一个名称、类型和可选的默认值（如果省略，则默认为`0`或`NULL`）。

表中每个字段都是可选的：它不必出现在线路表示中，您可以选择忽略每个对象的字段。因此，您可以灵活地添加字段，而不必担心数据膨胀。此设计也是 FlatBuffer 的向前和向后兼容机制。请注意：

*  在 schema 文件中只能在表定义的末尾添加新字段。旧数据仍能正确读取，并在读取时为您提供默认值。旧代码只会忽略新字段。如果想要灵活地对 schema 中的字段使用任何顺序，则可以手动分配 id（与 Protocol Buffers 类似），请参见下面的 id 属性。
 *  您无法从 schema 中删除不再使用的字段，但是您可以停止将它们写入数据中以达到几乎相同的效果。另外，您可以像上面的示例中那样将它们标记为已弃用，这将防止在生成的 C++中生成访问器，从而强制不再使用该字段。（小心：这可能会破坏代码！）。
 *  您可以更改字段名和表名，如果您不介意同步更改代码重命名。

Struct 没有一个字段是可选的（因此也没有默认值），并且不能添加或弃用字段。只能包含标量或其他结构。对于简单的对象，如果您确定不会进行任何更改（如示例中`Vec3`非常明确）。结构使用的内存比表少，访问速度更快（它们始终以内联方式存储在其父对象中，并且不使用虚拟表）。

`union`与枚举的许多属性相同，但是使用表名而不是常量的名称。声明的一个联合字段中可以包含对任何这些类型的引用，并且还会生成带有后缀`_type`的隐藏字段，其中包含相应的枚举值，使您能够在运行时知道要转换为哪种类型。

联合体是一种能够将多种消息类型作为 FlatBuffer 发送的好方法。请注意，由于联合字段实际上是两个字段，因此它必须始终是表的一部分，本身不能成为 FlatBuffer 的根。

下面代码生成的结构体在`MyGame::Sample`命名空间中。

namespace MyGame.Sample;
    
    enum Color:byte {
         Red = 0, Green, Blue = 2 }
    
    union Equipment {
         Weapon } // Optionally add more tables.
    
    struct Vec3 {
        
      x:float;
      y:float;
      z:float;
    }
    
    table Monster {
        
      pos:Vec3;
      mana:short = 150;
      hp:short = 100;
      name:string;
      friendly:bool = false (deprecated);
      inventory:[ubyte];
      color:Color = Blue;
      weapons:[Weapon];
      equipped:Equipment;
      path:[Vec3];
    }
    
    table Weapon {
        
      name:string;
      damage:short;
    }
    
    root_type Monster;

## [sample\_binary.cpp][sample_binary.cpp] ##

FlatBuffers 中有内部定义的 [Vector][] 和 [String][]。标量可以直接保存，其他成员都需要独立构建后再加入所隶属的结构中。

[FlatBufferBuilder][] 是用于容纳创建 FlatBuffer 所需数据的帮助程序类。  
[FlatBufferBuilder::FlatBufferBuilder][FlatBufferBuilder_FlatBufferBuilder]  
要序列化数据，通常调用生成代码中的一个`Create*()`函数，该函数依次调用`StartTable/PushElement/AddElement/EndTable`序列或内置的 [CreateString][]/[CreateVector][] 函数。这样做是以深度优先顺序在根部建立一棵树。[Finish()][Finish] 将缓冲区打包以备传输。

[FlatBufferBuilder::CreateString][FlatBufferBuilder_CreateString] 在缓冲区中存储一个字符串，该字符串可以包含任何二进制数据。返回字符串开始处的缓冲区中的偏移量。

// Build up a serialized buffer algorithmically:
      flatbuffers::FlatBufferBuilder builder;
    
      // First, lets serialize some weapons for the Monster: A 'sword' and an 'axe'.
      auto weapon_one_name = builder.CreateString("Sword");
      short weapon_one_damage = 3;
    
      auto weapon_two_name = builder.CreateString("Axe");
      short weapon_two_damage = 5;

[CreateWeapon][] 构建出 [Weapon][] 对象，返回对象的偏移。`weapons_vector`为偏移构成的数组。  
[FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector] 将偏移数组存储起来。

// Use the `CreateWeapon` shortcut to create Weapons with all fields set.
      auto sword = CreateWeapon(builder, weapon_one_name, weapon_one_damage);
      auto axe = CreateWeapon(builder, weapon_two_name, weapon_two_damage);
    
      // Create a FlatBuffer's `vector` from the `std::vector`.
      std::vector<flatbuffers::Offset<Weapon>> weapons_vector;
      weapons_vector.push_back(sword);
      weapons_vector.push_back(axe);
      auto weapons = builder.CreateVector(weapons_vector);

接受数组的 [FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector 1] 将数组值存储起来并返回数组偏移`inventory`。  
[FlatBufferBuilder::Finish()][FlatBufferBuilder_Finish] 通过写入根偏移量完成缓冲区的序列化。

// Second, serialize the rest of the objects needed by the Monster.
      auto position = Vec3(1.0f, 2.0f, 3.0f);
    
      auto name = builder.CreateString("MyMonster");
    
      unsigned char inv_data[] = {
         0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
      auto inventory = builder.CreateVector(inv_data, 10);

[CreateMonster][] 通过 [MonsterBuilder][] 来构造出 [Monster][FlatBufferBuilder_CreateVector 1] 对象。

// Shortcut for creating monster with all fields set:
      auto orc = CreateMonster(builder, &position, 150, 80, name, inventory,
                               Color_Red, weapons, Equipment_Weapon, axe.Union());
    
      builder.Finish(orc);  // Serialize the root of the object.

解析缓冲区。  
[FlatBufferBuilder::GetBufferPointer][FlatBufferBuilder_GetBufferPointer] 获取序列化的缓冲区（在调用 [Finish()][Finish] 之后）。  
[GetMonster][] 调用 [GetRoot][] 获得 [Monster][] 对象的指针。

// We now have a FlatBuffer we can store on disk or send over a network.
    
      // ** file/network code goes here :) **
      // access builder.GetBufferPointer() for builder.GetSize() bytes
    
      // Instead, we're going to access it right away (as if we just received it).
    
      // Get access to the root:
      auto monster = GetMonster(builder.GetBufferPointer());

[Monster::hp][Monster_hp] 和 [Monster::mana][Monster_mana] 通过 [Table::GetField][Table_GetField] 获得字段值。  
[Monster::name][Monster_name] 通过 [Table::GetPointer][Table_GetPointer] 获得 [String][] 对象的指针。  
[Monster::pos][Monster_pos] 调用 [Table::GetStruct][Table_GetStruct] 得到 [Vec3][] 结构体的指针。

// Get and test some scalar types from the FlatBuffer.
      assert(monster->hp() == 80);
      assert(monster->mana() == 150);  // default
      assert(monster->name()->str() == "MyMonster");
    
      // Get and test a field of the FlatBuffer's `struct`.
      auto pos = monster->pos();
      assert(pos);
      assert(pos->z() == 3.0f);
      (void)pos;

[Monster::inventory][Monster_inventory] 通过 [Table::GetPointer][Table_GetPointer] 获取 [Vector][] 对象的指针。  
[Vector::Get][Vector_Get] 获取指定索引的元素。  
[Monster::weapons][Monster_weapons] 通过 [Table::GetPointer][Table_GetPointer] 获取 [Vector][] 对象的指针`weps`。后者记录了每个 [Weapon][] 对象的偏移，从而能够调用 [Weapon::name][Weapon_name] 和 [Weapon::damage][Weapon_damage]。

// Get a test an element from the `inventory` FlatBuffer's `vector`.
      auto inv = monster->inventory();
      assert(inv);
      assert(inv->Get(9) == 9);
      (void)inv;
    
      // Get and test the `weapons` FlatBuffers's `vector`.
      std::string expected_weapon_names[] = {
         "Sword", "Axe" };
      short expected_weapon_damages[] = {
         3, 5 };
      auto weps = monster->weapons();
      for (unsigned int i = 0; i < weps->size(); i++) {
        
        assert(weps->Get(i)->name()->str() == expected_weapon_names[i]);
        assert(weps->Get(i)->damage() == expected_weapon_damages[i]);
      }
      (void)expected_weapon_names;
      (void)expected_weapon_damages;

[Monster::equipped\_type][Monster_equipped_type] 通过 [Table::GetField][Table_GetField] 获得 [Equipment][] 枚举值。

// Get and test the `Equipment` union (`equipped` field).
      assert(monster->equipped_type() == Equipment_Weapon);
      auto equipped = static_cast<const Weapon *>(monster->equipped());
      assert(equipped->name()->str() == "Axe");
      assert(equipped->damage() == 5);
      (void)equipped;
    
      printf("The FlatBuffer was successfully created and verified!\n");

## [FlatBufferBuilder::CreateString][FlatBufferBuilder_CreateString] ##

[FlatBufferBuilder::NotNested][FlatBufferBuilder_NotNested] 检查构建过程中是否存在嵌套。  
[FlatBufferBuilder::PreAlign][FlatBufferBuilder_PreAlign] 向`buf_`填0，预先进行对齐。  
[FlatBufferBuilder::PushBytes][FlatBufferBuilder_PushBytes] 将数据填入`buf_`中。  
[FlatBufferBuilder::PushElement][FlatBufferBuilder_PushElement] 把长度值追加进去。  
[FlatBufferBuilder::GetSize][FlatBufferBuilder_GetSize] 返回当前大小。

/// @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());
      }

## [CreateWeapon][] ##

创建一个 [WeaponBuilder][]，由后者进行构造。  
[WeaponBuilder::add\_name][WeaponBuilder_add_name] 记录`name`的偏移。  
[WeaponBuilder::add\_damage][WeaponBuilder_add_damage] 保存`damage`的值。  
[WeaponBuilder::Finish][WeaponBuilder_Finish] 生成 vtable。

inline flatbuffers::Offset<Weapon> CreateWeapon(
        flatbuffers::FlatBufferBuilder &_fbb,
        flatbuffers::Offset<flatbuffers::String> name = 0,
        int16_t damage = 0) {
        
      WeaponBuilder builder_(_fbb);
      builder_.add_name(name);
      builder_.add_damage(damage);
      return builder_.Finish();
    }

## [WeaponBuilder][] ##

[FlatBufferBuilder::AddOffset][FlatBufferBuilder_AddOffset] 插入偏移量。  
[Offset][] 用于 [uoffset\_t][uoffset_t] 的包装器，可进行安全的模板特化。  
[FlatBufferBuilder::EndTable][FlatBufferBuilder_EndTable] 完成了一个序列化对象，方法是生成 vtable（如果是表），将其与现有vtable进行比较，然后写入生成的 vtable 偏移量。

struct WeaponBuilder {
        
      typedef Weapon Table;
      flatbuffers::FlatBufferBuilder &fbb_;
      flatbuffers::uoffset_t start_;
      void add_name(flatbuffers::Offset<flatbuffers::String> name) {
        
        fbb_.AddOffset(Weapon::VT_NAME, name);
      }
      void add_damage(int16_t damage) {
        
        fbb_.AddElement<int16_t>(Weapon::VT_DAMAGE, damage, 0);
      }
      explicit WeaponBuilder(flatbuffers::FlatBufferBuilder &_fbb)
            : fbb_(_fbb) {
        
        start_ = fbb_.StartTable();
      }
      flatbuffers::Offset<Weapon> Finish() {
        
        const auto end = fbb_.EndTable(start_);
        auto o = flatbuffers::Offset<Weapon>(end);
        return o;
      }
    };

## [Weapon][] ##

[WeaponT][] 为表的对象结构体（T 结尾符），该结构体可以直接进行数据操作。MNN 中采用这种结构体和 Pack 函数完成序列化。

struct Weapon FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table {
        
      typedef WeaponT NativeTableType;
      typedef WeaponBuilder Builder;
      static const flatbuffers::TypeTable *MiniReflectTypeTable() {
        
        return WeaponTypeTable();
      }
      enum FlatBuffersVTableOffset FLATBUFFERS_VTABLE_UNDERLYING_TYPE {
        
        VT_NAME = 4,
        VT_DAMAGE = 6
      };
      const flatbuffers::String *name() const {
        
        return GetPointer<const flatbuffers::String *>(VT_NAME);
      }
      flatbuffers::String *mutable_name() {
        
        return GetPointer<flatbuffers::String *>(VT_NAME);
      }
      int16_t damage() const {
        
        return GetField<int16_t>(VT_DAMAGE, 0);
      }
      bool mutate_damage(int16_t _damage) {
        
        return SetField<int16_t>(VT_DAMAGE, _damage, 0);
      }
      bool Verify(flatbuffers::Verifier &verifier) const {
        
        return VerifyTableStart(verifier) &&
               VerifyOffset(verifier, VT_NAME) &&
               verifier.VerifyString(name()) &&
               VerifyField<int16_t>(verifier, VT_DAMAGE) &&
               verifier.EndTable();
      }
      WeaponT *UnPack(const flatbuffers::resolver_function_t *_resolver = nullptr) const;
      void UnPackTo(WeaponT *_o, const flatbuffers::resolver_function_t *_resolver = nullptr) const;
      static flatbuffers::Offset<Weapon> Pack(flatbuffers::FlatBufferBuilder &_fbb, const WeaponT* _o, const flatbuffers::rehasher_function_t *_rehasher = nullptr);
    };

## [Offset][] ##

用于 [voffset\_t][voffset_t] 的包装器，可进行安全的模板特化。

// 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; }
    };

## [FlatBufferBuilder::AddOffset][FlatBufferBuilder_AddOffset] ##

FlatBufferBuilder::AddOffset

FlatBufferBuilder::AddElement

[FlatBufferBuilder::AddElement][FlatBufferBuilder_AddElement]  
[FlatBufferBuilder::ReferTo][FlatBufferBuilder_ReferTo]  
[voffset\_t][voffset_t]

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));
      }

## [FlatBufferBuilder::AddElement][FlatBufferBuilder_AddElement] ##

FlatBufferBuilder::AddElement

FlatBufferBuilder::PushElement

FlatBufferBuilder::TrackField

插入字段和值。  
[IsTheSameAs][] 判断两个标量值是否相等。  
[FlatBufferBuilder::PushElement][FlatBufferBuilder_PushElement] 将单个对齐的标量写入缓冲区并返回缓冲区大小。  
[FlatBufferBuilder::TrackField][FlatBufferBuilder_TrackField] 将 [FieldLoc][] 结构体插入到`buf_`中。

// 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 (IsTheSameAs(e, def) && !force_defaults_) return;
        auto off = PushElement(e);
        TrackField(field, off);
      }

## [FlatBufferBuilder::TrackField][FlatBufferBuilder_TrackField] ##

FlatBufferBuilder::TrackField

vector\_downward::scratch\_push\_small

构造一个 [FieldLoc][] 结构体。  
[vector\_downward::scratch\_push\_small][vector_downward_scratch_push_small] 将数据插入向量的最低地址中。

// 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 };
        buf_.scratch_push_small(fl);
        num_field_loc++;
        max_voffset_ = (std::max)(max_voffset_, field);
      }

## [FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector] ##

调用使用数组指针的版本。

/// @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());
      }

## [FlatBufferBuilder::ReferTo][FlatBufferBuilder_ReferTo] ##

// 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.
        FLATBUFFERS_ASSERT(off && off <= GetSize());
        return GetSize() - off + static_cast<uoffset_t>(sizeof(uoffset_t));
      }

## [FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector 2] ##

[FlatBufferBuilder::EndVector][FlatBufferBuilder_EndVector] 插入数组长度并返回偏移。

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));
      }

## [FlatBufferBuilder::StartVector][FlatBufferBuilder_StartVector] ##

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.
      }

## [FlatBufferBuilder::PushElement][FlatBufferBuilder_PushElement 1] ##

访问其中的偏移值。

template<typename T> uoffset_t PushElement(Offset<T> off) {
        
        // Special case for offsets: see ReferTo below.
        return PushElement(ReferTo(off.o));
      }

## [FlatBufferBuilder::PushElement][FlatBufferBuilder_PushElement] ##

[AssertScalarT][] 检查`T`类型是否为标量。  
[Align][] 对`buf_`进行填充。  
[EndianScalar][] 得到小端值。  
[FlatBufferBuilder::GetSize][FlatBufferBuilder_GetSize] 返回`buf_`的大小。

// 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();
      }

## [FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector] ##

[data][] 对于空向量返回非 null 以避免未定义的行为。因为最终返回的指针被传递给 memcpy，所以需要它。

## [FlatBufferBuilder::CreateVector][FlatBufferBuilder_CreateVector 2] ##

[FlatBufferBuilder::StartVector][FlatBufferBuilder_StartVector]  
以倒序方式插入

## [CreateMonster][] ##

CreateMonster

MonsterBuilder

调用 [MonsterBuilder][]

inline flatbuffers::Offset<Monster> CreateMonster(
        flatbuffers::FlatBufferBuilder &_fbb,
        const MyGame::Sample::Vec3 *pos = 0,
        int16_t mana = 150,
        int16_t hp = 100,
        flatbuffers::Offset<flatbuffers::String> name = 0,
        flatbuffers::Offset<flatbuffers::Vector<uint8_t>> inventory = 0,
        MyGame::Sample::Color color = MyGame::Sample::Color_Blue,
        flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<MyGame::Sample::Weapon>>> weapons = 0,
        MyGame::Sample::Equipment equipped_type = MyGame::Sample::Equipment_NONE,
        flatbuffers::Offset<void> equipped = 0,
        flatbuffers::Offset<flatbuffers::Vector<const MyGame::Sample::Vec3 *>> path = 0) {
        
      MonsterBuilder builder_(_fbb);
      builder_.add_path(path);
      builder_.add_equipped(equipped);
      builder_.add_weapons(weapons);
      builder_.add_inventory(inventory);
      builder_.add_name(name);
      builder_.add_pos(pos);
      builder_.add_hp(hp);
      builder_.add_mana(mana);
      builder_.add_equipped_type(equipped_type);
      builder_.add_color(color);
      return builder_.Finish();
    }

## [MonsterBuilder][] ##

struct MonsterBuilder {
        
      typedef Monster Table;
      flatbuffers::FlatBufferBuilder &fbb_;
      flatbuffers::uoffset_t start_;
      void add_pos(const MyGame::Sample::Vec3 *pos) {
        
        fbb_.AddStruct(Monster::VT_POS, pos);
      }
      void add_mana(int16_t mana) {
        
        fbb_.AddElement<int16_t>(Monster::VT_MANA, mana, 150);
      }
      void add_hp(int16_t hp) {
        
        fbb_.AddElement<int16_t>(Monster::VT_HP, hp, 100);
      }
      void add_name(flatbuffers::Offset<flatbuffers::String> name) {
        
        fbb_.AddOffset(Monster::VT_NAME, name);
      }
      void add_inventory(flatbuffers::Offset<flatbuffers::Vector<uint8_t>> inventory) {
        
        fbb_.AddOffset(Monster::VT_INVENTORY, inventory);
      }
      void add_color(MyGame::Sample::Color color) {
        
        fbb_.AddElement<int8_t>(Monster::VT_COLOR, static_cast<int8_t>(color), 2);
      }
      void add_weapons(flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<MyGame::Sample::Weapon>>> weapons) {
        
        fbb_.AddOffset(Monster::VT_WEAPONS, weapons);
      }
      void add_equipped_type(MyGame::Sample::Equipment equipped_type) {
        
        fbb_.AddElement<uint8_t>(Monster::VT_EQUIPPED_TYPE, static_cast<uint8_t>(equipped_type), 0);
      }
      void add_equipped(flatbuffers::Offset<void> equipped) {
        
        fbb_.AddOffset(Monster::VT_EQUIPPED, equipped);
      }
      void add_path(flatbuffers::Offset<flatbuffers::Vector<const MyGame::Sample::Vec3 *>> path) {
        
        fbb_.AddOffset(Monster::VT_PATH, path);
      }
      explicit MonsterBuilder(flatbuffers::FlatBufferBuilder &_fbb)
            : fbb_(_fbb) {
        
        start_ = fbb_.StartTable();
      }
      flatbuffers::Offset<Monster> Finish() {
        
        const auto end = fbb_.EndTable(start_);
        auto o = flatbuffers::Offset<Monster>(end);
        return o;
      }
    };

## 参考资料： ##

*  [Tutorial][]
 *  [Difference between char and signed char in c++?][Difference between char and signed char in c]
 *  [Can I reinterpret std::vector as a std::vector without copying?][Can I reinterpret std_vector as a std_vector without copying]
 *  [FlatBuffers介绍及初步试用][FlatBuffers]
 *  [Writing a schema][]
 *  [android FlatBuffers剖析][android FlatBuffers]
 *  [FlatBuffers学习总结][FlatBuffers 1]
 *  [Flatbuffers使用解析][Flatbuffers]
 *  [FlatBuffer Internals][]
 *  [FlatBuffers white paper][]
 *  [how to feed data from binary string ubyte vector of flatbuffer in python?][how to feed data from binary string ubyte vector of flatbuffer in python]
 *  [深入浅出 FlatBuffers 之 Encode][FlatBuffers _ Encode]
 *  [数据序列化组件PB与FB对比][PB_FB]
 *  [FlatBuffer代码阅读 - 1 ][FlatBuffer_ - 1]
 *  [Applied SOAP: Implementing .NET XML Web Services by Kenn Scribner, Mark Stiver][Applied SOAP_ Implementing .NET XML Web Services by Kenn Scribner_ Mark Stiver]
 *  [Git 协议版本 2 宣布推出：Git wire protocol 的一次重大更新][Git _ 2 _Git wire protocol]
 *  [什么是wire protocol？][wire protocol]
 *  [What is wire format][]
 *  [Class WireFormat][]
 *  [Wire protocol][]
 *  [XML wire format][]
 *  [flatbuffer的数组小例子（C++）][flatbuffer_C]
 *  [General rules of passing/returning reference of array (not pointer) to/from a function?][General rules of passing_returning reference of array _not pointer_ to_from a function]
 *  [Return array in a function][]
 *  [flatbuffer编码的内存的结构][flatbuffer]
 *  [FlatBuffers反射][FlatBuffers 2]
 *  [caffe模型文件解析\_MNN模型转化的主流程][caffe_MNN]
 *  [Why cast an unused function parameter value to void?][Why cast an unused function parameter value to void]

[monster.fbs]: https://github.com/google/flatbuffers/blob/master/samples/monster.fbs
[sample_binary.cpp]: https://github.com/google/flatbuffers/blob/master/samples/sample_binary.cpp#L23
[Vector]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L243
[String]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L616
[FlatBufferBuilder]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1132
[FlatBufferBuilder_FlatBufferBuilder]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1145
[CreateString]: https://google.github.io/flatbuffers/classflatbuffers_1_1_flat_buffer_builder.html#aec6f9df2a0366b540b24822414d92cbe
[CreateVector]: https://google.github.io/flatbuffers/classflatbuffers_1_1_flat_buffer_builder.html#a2cca5c89246a53e80e6ad9487f4c36f3
[Finish]: https://google.github.io/flatbuffers/classflatbuffers_1_1_flat_buffer_builder.html#a0c9e507b373d598b51052fab4fa34912
[FlatBufferBuilder_CreateString]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1534
[CreateWeapon]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L539
[Weapon]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L484
[FlatBufferBuilder_CreateVector]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1727
[FlatBufferBuilder_CreateVector 1]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1692
[FlatBufferBuilder_Finish]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2070
[CreateMonster]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L409
[MonsterBuilder]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L364
[FlatBufferBuilder_GetBufferPointer]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1238
[GetMonster]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L823
[GetRoot]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2180
[Monster]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L256
[Monster_hp]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L286
[Monster_mana]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L280
[Table_GetField]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2528
[Monster_name]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L292
[Table_GetPointer]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2539
[Monster_pos]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L274
[Table_GetStruct]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2543
[Vec3]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L172
[Monster_inventory]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L298
[Vector_Get]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L262
[Monster_weapons]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L310
[Weapon_name]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L494
[Weapon_damage]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L500
[Monster_equipped_type]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L316
[Equipment]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L68
[FlatBufferBuilder_NotNested]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1407
[FlatBufferBuilder_PreAlign]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1520
[FlatBufferBuilder_PushBytes]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1335
[FlatBufferBuilder_PushElement]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1345
[FlatBufferBuilder_GetSize]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1233
[WeaponBuilder]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L518
[WeaponBuilder_add_name]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L522
[WeaponBuilder_add_damage]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L525
[WeaponBuilder_Finish]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L532
[FlatBufferBuilder_AddOffset]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1380
[Offset]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L67
[uoffset_t]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/base.h#L316
[FlatBufferBuilder_EndTable]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1432
[WeaponT]: https://github.com/google/flatbuffers/blob/master/samples/monster_generated.h#L467
[voffset_t]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/base.h#L323
[FlatBufferBuilder_AddElement]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1368
[FlatBufferBuilder_ReferTo]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1399
[IsTheSameAs]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L35
[FlatBufferBuilder_TrackField]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1360
[FieldLoc]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L2113
[vector_downward_scratch_push_small]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1028
[FlatBufferBuilder_CreateVector 2]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1715
[FlatBufferBuilder_EndVector]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1654
[FlatBufferBuilder_StartVector]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1660
[FlatBufferBuilder_PushElement 1]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1353
[AssertScalarT]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1339
[Align]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1325
[EndianScalar]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/base.h#L390
[data]: https://github.com/google/flatbuffers/blob/master/include/flatbuffers/flatbuffers.h#L1108
[Tutorial]: https://google.github.io/flatbuffers/flatbuffers_guide_tutorial.html
[Difference between char and signed char in c]: https://stackoverflow.com/questions/16503373/difference-between-char-and-signed-char-in-c
[Can I reinterpret std_vector as a std_vector without copying]: https://stackoverflow.com/questions/41462433/can-i-reinterpret-stdvectorchar-as-a-stdvectorunsigned-char-without-copy
[FlatBuffers]: https://blog.csdn.net/qq_35559358/article/details/79443327
[Writing a schema]: https://google.github.io/flatbuffers/md__schemas.html
[android FlatBuffers]: https://blog.csdn.net/yxz329130952/article/details/50880191
[FlatBuffers 1]: https://www.dazhuanlan.com/2020/02/10/5e40e85e22ec4/?__cf_chl_jschl_tk__=4d645ef7bb03432c57010e0e35e6c7556ab2f849-1600586638-0-AdbslnMzdlI3_eC-MfZ_1O396d7dgPdWfHFCNpFHcAMLsEPH6pfLaKBlOXV1c8Yo_2BXXghnKVPE12WTNFfhMQU_NjI86ArF82FkhhO6cvN6ZQ_OAIaooS0mUbJSNckG5dTgsWZeFk_Y7JP24LFGfE6kwm16zM3R-FsRh9rJq3N4yxIL_WahAhbQj8oSkdSXWuk1Kc1lsoD4TBNvKVUeViX16eiQYyHxvaVIEPkBkXpPRHNMsEFtF7kuxufeMDL2HJXbPigUiNod6LAZL3nwq8Xkt4iIcSgAv6BXceuhvSX0SDPJAqkiviGuxd0Xe2ntPQ
[Flatbuffers]: https://blog.csdn.net/sudao000/article/details/53385376/
[FlatBuffer Internals]: https://google.github.io/flatbuffers/md__internals.html
[FlatBuffers white paper]: https://google.github.io/flatbuffers/flatbuffers_white_paper.html
[how to feed data from binary string ubyte vector of flatbuffer in python]: https://stackoverflow.com/questions/42679373/how-to-feed-data-from-binary-string-ubyte-vector-of-flatbuffer-in-python
[FlatBuffers _ Encode]: https://halfrost.com/flatbuffers_encode/
[PB_FB]: https://juzii.gitee.io/2020/03/02/protobuf-vs-flatbuffer/
[FlatBuffer_ - 1]: https://wizmann.tk/read-flatbuffer-1.html
[Applied SOAP_ Implementing .NET XML Web Services by Kenn Scribner_ Mark Stiver]: https://www.oreilly.com/library/view/applied-soap-implementing/0672321114/0672321114_ch03lev1sec1.html
[Git _ 2 _Git wire protocol]: https://www.sohu.com/a/232308683_465914
[wire protocol]: https://www.zhihu.com/question/413112626
[What is wire format]: https://www.toolbox.com/tech/enterprise-software/question/what-is-wire-format-080306/
[Class WireFormat]: https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/WireFormat
[Wire protocol]: https://en.wikipedia.org/wiki/Wire_protocol
[XML wire format]: https://www.ibm.com/support/knowledgecenter/en/SSQ2R2_9.1.1/com.ibm.etools.est.doc/ref/rsfmsg005.html
[flatbuffer_C]: https://blog.csdn.net/pengshengli/article/details/100864148
[General rules of passing_returning reference of array _not pointer_ to_from a function]: https://stackoverflow.com/questions/5398930/general-rules-of-passing-returning-reference-of-array-not-pointer-to-from-a-fu/25169202
[Return array in a function]: https://stackoverflow.com/questions/3473438/return-array-in-a-function
[flatbuffer]: https://blog.csdn.net/weixin_42869573/article/details/83820166
[FlatBuffers 2]: https://harmonyhu.com/2019/02/03/flatbuffers-reflection/
[caffe_MNN]: https://blog.csdn.net/weixin_39994806/article/details/111672659
[Why cast an unused function parameter value to void]: https://stackoverflow.com/questions/4647665/why-cast-an-unused-function-parameter-value-to-void