比特币源码阅读(交易-CTransaction)

https://en.bitcoin.it/wiki/Protocol_documentation#tx

2018-07-27 17-29-16 的屏幕截图.png

src/primitives/transaction.h

/** The basic transaction that is broadcasted on the network and contained in
 * blocks.  A transaction can contain multiple inputs and outputs.
 */
class CTransaction
{
public:
    // Default transaction version.
    static const int32_t CURRENT_VERSION=2;

    // Changing the default transaction version requires a two step process: first
    // adapting relay policy by bumping MAX_STANDARD_VERSION, and then later date
    // bumping the default CURRENT_VERSION at which point both CURRENT_VERSION and
    // MAX_STANDARD_VERSION will be equal.
    static const int32_t MAX_STANDARD_VERSION=2;

    // The local variables are made const to prevent unintended modification
    // without updating the cached hash value. However, CTransaction is not
    // actually immutable(不变的); deserialization and assignment are implemented,
    // and bypass the constness. This is safe, as they update the entire
    // structure, including the hash.
    const std::vector<CTxIn> vin; //输入
    const std::vector<CTxOut> vout; //输出
    const int32_t nVersion;
    const uint32_t nLockTime;

private:
    /** Memory only. */
    const uint256 hash;
    const uint256 m_witness_hash;

    uint256 ComputeHash() const; //所以区块浏览器上面的交易hash其实是算出来的，不是本来就存在与交易的数据结构中
    uint256 ComputeWitnessHash() const;

public:
    /** Construct a CTransaction that qualifies as IsNull() */
    CTransaction();

    /** Convert a CMutableTransaction into a CTransaction. */
    CTransaction(const CMutableTransaction &tx);
    CTransaction(CMutableTransaction &&tx);

    template <typename Stream>
    inline void Serialize(Stream& s) const {
        SerializeTransaction(*this, s);
    }

    /** This deserializing constructor is provided instead of an Unserialize method.
     *  Unserialize is not possible, since it would require overwriting const fields. */
    template <typename Stream>
    CTransaction(deserialize_type, Stream& s) : CTransaction(CMutableTransaction(deserialize, s)) {}

    bool IsNull() const {
        return vin.empty() && vout.empty();
    }

    const uint256& GetHash() const { return hash; }
    const uint256& GetWitnessHash() const { return m_witness_hash; };

    // Return sum of txouts.
    CAmount GetValueOut() const;
    // GetValueIn() is a method on CCoinsViewCache, because
    // inputs must be known to compute value in.

    /**
     * Get the total transaction size in bytes, including witness data.
     * "Total Size" defined in BIP141 and BIP144.
     * @return Total transaction size in bytes
     */
    unsigned int GetTotalSize() const;

    bool IsCoinBase() const
    {
        return (vin.size() == 1 && vin[0].prevout.IsNull()); //是否为CoinBase的判断方法
    }

    friend bool operator==(const CTransaction& a, const CTransaction& b)
    {
        return a.hash == b.hash; //hash相等
    }

    friend bool operator!=(const CTransaction& a, const CTransaction& b)
    {
        return a.hash != b.hash; //hash不等
    }

    std::string ToString() const;

    bool HasWitness() const
    {
        for (size_t i = 0; i < vin.size(); i++) {
            if (!vin[i].scriptWitness.IsNull()) //会不会存在部分vin存在scriptWitness（）
                return true;
            }
        }
        return false;
    }
};