Bitcoin序列化库使用

Bitcoin序列化功能主要实现在serialize.h文件，整个代码主要是围绕stream和参与序列化反序列化的类型T展开。

stream这个模板形参表达具有read(char**, size_t) 和write(char**, size_t)方法的对象，类似Golang 的io.reader ,io.writer。

简单的使用例子：

#include <serialize.h> #include <streams.h> #include <hash.h> #include <test/test_bitcoin.h>  #include <stdint.h> #include <memory>  #include <boost/test/unit_test.hpp>  BOOST_FIXTURE_TEST_SUITE(serialize_tests, BasicTestingSetup)   struct  student {     std::string name;     double midterm, final;     std::vector<double> homework;      ADD_SERIALIZE_METHODS;      template <typename Stream, typename Operation>     inline void SerializationOp(Stream& s, Operation ser_action) {         READWRITE(name);         READWRITE(midterm);         READWRITE(final);         READWRITE(homework);     }          };  bool operator==(student const& lhs,  student const& rhs){         return lhs.name == rhs.name &&  \                lhs.midterm ==  rhs.midterm && \                lhs.final  ==  rhs.final && \                lhs.homework == rhs.homework; }  std::ostream& operator<<(std::ostream& os, student const& st){         os << "name: " << st.name << '\n'             << "midterm: " << st.midterm << '\n'            << "final: "   << st.final  << '\n'            << "homework: " ;         for (auto e : st.homework) {             os << e <<  ' ';         }         return os; }   BOOST_AUTO_TEST_CASE(normal) {     student  s, t;     s.name = "john";     s.midterm = 77;     s.final = 82;     auto  v = std::vector<double> {83, 50, 10, 88, 65};     s.homework = v;      CDataStream ss(SER_DISK, 0);     ss <<  s;     ss >>  t;       BOOST_CHECK(t.name  == "john");     BOOST_CHECK(t.midterm  == 77);     BOOST_CHECK(t.final  == 82);     BOOST_TEST(t.homework == v,  boost::test_tools::per_element());            CDataStream sd(SER_DISK, 0);     CDataStream sn(SER_NETWORK, PROTOCOL_VERSION);     sd << s;     sn << s;     BOOST_CHECK(Hash(sd.begin(), sd.end()) == Hash(sn.begin(), sn.end())); }  BOOST_AUTO_TEST_CASE(vector) {     auto vs = std::vector<student>(3);     vs[0].name = "bob";     vs[0].midterm = 90;     vs[0].final = 76;     vs[0].homework = std::vector<double> {85, 53, 12, 75, 55};      vs[1].name = "jim";     vs[1].midterm = 96;     vs[1].final = 72;     vs[1].homework = std::vector<double> {91, 46, 19, 70, 59};      vs[2].name = "tom";     vs[2].midterm = 85;     vs[2].final = 57;     vs[2].homework = std::vector<double> {91, 77, 45, 50, 35};       CDataStream ss(SER_DISK, 0);     auto vt = std::vector<student>(3);     ss <<  vs;     ss >>  vt;       BOOST_TEST(vs == vt,  boost::test_tools::per_element());  }  BOOST_AUTO_TEST_CASE(unique_ptr){     auto hex = "0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba26000000000490047304402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e1681a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696ad990364e555c271ad504b88ac00000000";     CDataStream stream(ParseHex(hex), SER_NETWORK, PROTOCOL_VERSION);         //CTransaction tx(deserialize, stream);     auto utx = std::unique_ptr<const CTransaction>(nullptr);     ::Unserialize(stream, utx);     BOOST_TEST(utx->vin.size() == std::size_t(1));     BOOST_TEST(utx->vout[0].nValue == 1000000); }  BOOST_AUTO_TEST_SUITE_END()

需要在用户的自定义类型内部添加 ADD_SERIALIZE_METHODS 调用，宏展开后：

template<typename Stream>                                         \     void Serialize(Stream& s) const {                                 \         NCONST_PTR(this)->SerializationOp(s, CSerActionSerialize());  \     }                                                                 \     template<typename Stream>                                         \     void Unserialize(Stream& s) {                                     \         SerializationOp(s, CSerActionUnserialize());                  \     }

这个宏为用户自定义类型添加了两个成员函数： Serialize 和 Unserialize，它们内部调用需要用户自定义的模板成员函数SerializationOp , 在 SerializationOp 函数内部，主要使用 READWRITE 和 READWRITEMANY 宏，完成对自定义类型每个数据成员的序列化与反序列化。

#define READWRITE(obj)      (::SerReadWrite(s, (obj), ser_action)) #define READWRITEMANY(...)      (::SerReadWriteMany(s, ser_action, __VA_ARGS__))  struct CSerActionSerialize {     constexpr bool ForRead() const { return false; } }; struct CSerActionUnserialize {     constexpr bool ForRead() const { return true; } };  template<typename Stream, typename T> inline void SerReadWrite(Stream& s, const T& obj, CSerActionSerialize ser_action) {     ::Serialize(s, obj); }  template<typename Stream, typename T> inline void SerReadWrite(Stream& s, T& obj, CSerActionUnserialize ser_action) {     ::Unserialize(s, obj); }  template<typename Stream, typename... Args> inline void SerReadWriteMany(Stream& s, CSerActionSerialize ser_action, Args&&... args) {     ::SerializeMany(s, std::forward<Args>(args)...); }  template<typename Stream, typename... Args> inline void SerReadWriteMany(Stream& s, CSerActionUnserialize ser_action, Args&... args) {     ::UnserializeMany(s, args...); }

需要在用户的自定义类型内部添加 ****ADD_SERIALIZE_METHODS**** 调用，宏展开后：

 template<typename Stream>  \   void Serialize(Stream& s) const {  \   NCONST_PTR(this)->SerializationOp(s, CSerActionSerialize()); \   }  \   template<typename Stream>  \   void Unserialize(Stream& s) {  \   SerializationOp(s, CSerActionUnserialize()); \   }

这个宏为用户自定义类型添加了两个成员函数： Serialize 和 Unserialize，它们内部调用需要用户自定义的模板成员函数SerializationOp , 在 SerializationOp 函数内部，主要使用 READWRITE 和 READWRITEMANY 宏，完成对自定义类型每个数据成员的序列化与反序列化。

#define READWRITE(obj)      (::SerReadWrite(s, (obj), ser_action)) #define READWRITEMANY(...)      (::SerReadWriteMany(s, ser_action, __VA_ARGS__))  struct CSerActionSerialize {     constexpr bool ForRead() const { return false; } }; struct CSerActionUnserialize {     constexpr bool ForRead() const { return true; } };  template<typename Stream, typename T> inline void SerReadWrite(Stream& s, const T& obj, CSerActionSerialize ser_action) {     ::Serialize(s, obj); }  template<typename Stream, typename T> inline void SerReadWrite(Stream& s, T& obj, CSerActionUnserialize ser_action) {     ::Unserialize(s, obj); }  template<typename Stream, typename... Args> inline void SerReadWriteMany(Stream& s, CSerActionSerialize ser_action, Args&&... args) {     ::SerializeMany(s, std::forward<Args>(args)...); }  template<typename Stream, typename... Args> inline void SerReadWriteMany(Stream& s, CSerActionUnserialize ser_action, Args&... args) {     ::UnserializeMany(s, args...); }

这里SerReadWrite 和 SerReadWriteMany 各自有两个overload 实现，区别是末尾分别传入了不同的类型CSerActionSerialize 和 CSerActionUnserialize , 而且形参 ser_action 根本没有在内部使用，查阅了相关资料，这里使用了c++ 泛型编程常用的一种模式：

tag dispatch 技术](https://akrzemi1.wordpress.com/examples/overloading-tag-dispatch/), 另一个解释:[https://arne-mertz.de/2016/10/tag-dispatch/)(https://arne-mertz.de/2016/10/tag-dispatch/)，

通过携带不同的类型，在编译时选择不同的overload 实现， CSerActionSerialize 对应序列化的实现， CSerActionUnserialize 对应反序列化的实现。

SerializeMany 和 SerializeMany是通过变长模板parameter pack 展开技术来实现，以 SerializeMany 为例子：

 template<typename Stream> void SerializeMany(Stream& s) { }  template<typename Stream, typename Arg> void SerializeMany(Stream& s, Arg&& arg) {     ::Serialize(s, std::forward<Arg>(arg)); }  template<typename Stream, typename Arg, typename... Args> void SerializeMany(Stream& s, Arg&& arg, Args&&... args) {     ::Serialize(s, std::forward<Arg>(arg));     ::SerializeMany(s, std::forward<Args>(args)...); }

SerializeMany有三个overload 实现,假设从上倒下,分别编号为1， 2， 3; 当我们传入两个以上的实参是,编译器选择版本3，版本3内部从parameter pack 弹出一个参数,然后传给版本2调用,剩下的参数列表，传给版本3，递归调用,直到parameter pack 为空时,选择版本1。

迂回这么长，最终序列化真正使用全局名称空间的 Serialize 来完成，反序列化通过调用Unserialize实现。

而 Serialize 和Unserialize 又有一堆的overload 实现， Bitcoin 作者实现一些常见类型的模板特化，比如，std::string, 主要设计表达脚本的prevector , std::vector, std::pair, std::map, std::set, std::unique_ptr, std::share_ptr 。 c++ 的模板匹配根据参数列表的匹配程度选择不同的实现，优先精准匹配，最后选择类型T的成员函数实现：

template<typename Stream, typename T> inline void Serialize(Stream& os, const T& a) {     a.Serialize(os); }  template<typename Stream, typename T> inline void Unserialize(Stream& is, T& a) {     a.Unserialize(is); }

在序列化string, map, set, vector, prevector 等可能包含多元素的集合类型时，内部会调用 ReadCompactSize和 WriteCompactSize读取写入紧凑编码的元素个数：

template<typename Stream> void WriteCompactSize(Stream& os, uint64_t nSize) {     if (nSize < 253)     {         ser_writedata8(os, nSize);     }     else if (nSize <= std::numeric_limits<unsigned short>::max())     {         ser_writedata8(os, 253);         ser_writedata16(os, nSize);     }     else if (nSize <= std::numeric_limits<unsigned int>::max())     {         ser_writedata8(os, 254);         ser_writedata32(os, nSize);     }     else     {         ser_writedata8(os, 255);         ser_writedata64(os, nSize);     }     return; }  template<typename Stream> uint64_t ReadCompactSize(Stream& is) {     uint8_t chSize = ser_readdata8(is);     uint64_t nSizeRet = 0;     if (chSize < 253)     {         nSizeRet = chSize;     }     else if (chSize == 253)     {         nSizeRet = ser_readdata16(is);         if (nSizeRet < 253)             throw std::ios_base::failure("non-canonical ReadCompactSize()");     }     else if (chSize == 254)     {         nSizeRet = ser_readdata32(is);         if (nSizeRet < 0x10000u)             throw std::ios_base::failure("non-canonical ReadCompactSize()");     }     else     {         nSizeRet = ser_readdata64(is);         if (nSizeRet < 0x100000000ULL)             throw std::ios_base::failure("non-canonical ReadCompactSize()");     }     if (nSizeRet > (uint64_t)MAX_SIZE)         throw std::ios_base::failure("ReadCompactSize(): size too large");     return nSizeRet; }

针对位宽1,2,4,8的基础类型，Serialize 和 Unserialize 最终调用ser_writedata, ser_readdata8 完成实现。

template<typename Stream> inline void Serialize(Stream& s, char a    ) { ser_writedata8(s, a); } // TODO Get rid of bare char template<typename Stream> inline void Serialize(Stream& s, int8_t a  ) { ser_writedata8(s, a); } template<typename Stream> inline void Serialize(Stream& s, uint8_t a ) { ser_writedata8(s, a); } template<typename Stream> inline void Serialize(Stream& s, int16_t a ) { ser_writedata16(s, a); } template<typename Stream> inline void Serialize(Stream& s, uint16_t a) { ser_writedata16(s, a); } template<typename Stream> inline void Serialize(Stream& s, int32_t a ) { ser_writedata32(s, a); } template<typename Stream> inline void Serialize(Stream& s, uint32_t a) { ser_writedata32(s, a); } template<typename Stream> inline void Serialize(Stream& s, int64_t a ) { ser_writedata64(s, a); } template<typename Stream> inline void Serialize(Stream& s, uint64_t a) { ser_writedata64(s, a); } template<typename Stream> inline void Serialize(Stream& s, float a   ) { ser_writedata32(s, ser_float_to_uint32(a)); } template<typename Stream> inline void Serialize(Stream& s, double a  ) { ser_writedata64(s, ser_double_to_uint64(a)); }  template<typename Stream> inline void Unserialize(Stream& s, char& a    ) { a = ser_readdata8(s); } // TODO Get rid of bare char template<typename Stream> inline void Unserialize(Stream& s, int8_t& a  ) { a = ser_readdata8(s); } template<typename Stream> inline void Unserialize(Stream& s, uint8_t& a ) { a = ser_readdata8(s); } template<typename Stream> inline void Unserialize(Stream& s, int16_t& a ) { a = ser_readdata16(s); } template<typename Stream> inline void Unserialize(Stream& s, uint16_t& a) { a = ser_readdata16(s); } template<typename Stream> inline void Unserialize(Stream& s, int32_t& a ) { a = ser_readdata32(s); } template<typename Stream> inline void Unserialize(Stream& s, uint32_t& a) { a = ser_readdata32(s); } template<typename Stream> inline void Unserialize(Stream& s, int64_t& a ) { a = ser_readdata64(s); } template<typename Stream> inline void Unserialize(Stream& s, uint64_t& a) { a = ser_readdata64(s); } template<typename Stream> inline void Unserialize(Stream& s, float& a   ) { a = ser_uint32_to_float(ser_readdata32(s)); } template<typename Stream> inline void Unserialize(Stream& s, double& a  ) { a = ser_uint64_to_double(ser_readdata64(s)); }  template<typename Stream> inline void Serialize(Stream& s, bool a)    { char f=a; ser_writedata8(s, f); } template<typename Stream> inline void Unserialize(Stream& s, bool& a) { char f=ser_readdata8(s); a=f; }

另外代码开始处的

struct deserialize_type {}; constexpr deserialize_type deserialize {};

作为tag 类型， tag 对象，主要为多个实现签名有以下形式：

template <typename Stream>  T::T(deserialize_type, Stream& s)

的反序列化构造器做分发，目前主要是CTransaction, CMutableTransaction 类型:

template <typename Stream>     CTransaction(deserialize_type, Stream& s) : CTransaction(CMutableTransaction(deserialize, s)) {}          template <typename Stream>     CMutableTransaction(deserialize_type, Stream& s) {         Unserialize(s);     }

文章来源: Bitcoin序列化库使用

标签

序列化

obj文件

test

vector

bitcoin

const

serialize