chain.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_CHAIN_H
#define BITCOIN_CHAIN_H

#include <arith_uint256.h>
#include <consensus/params.h>
#include <flatfile.h>
#include <kernel/cs_main.h>
#include <primitives/block.h>
#include <serialize.h>
#include <sync.h>
#include <uint256.h>
#include <util/time.h>

#include <algorithm>
#include <cassert>
#include <cstdint>
#include <string>
#include <vector>

static constexpr int64_t MAX_FUTURE_BLOCK_TIME = 2 * 60 * 60;

static constexpr int64_t TIMESTAMP_WINDOW = MAX_FUTURE_BLOCK_TIME;
static constexpr int32_t SEQ_ID_BEST_CHAIN_FROM_DISK = 0;
static constexpr int32_t SEQ_ID_INIT_FROM_DISK = 1;

enum BlockStatus : uint32_t {
    BLOCK_VALID_UNKNOWN      =    0,

    BLOCK_VALID_RESERVED     =    1,

    BLOCK_VALID_TREE         =    2,

    BLOCK_VALID_TRANSACTIONS =    3,

    BLOCK_VALID_CHAIN        =    4,

    BLOCK_VALID_SCRIPTS      =    5,

    BLOCK_VALID_MASK         =   BLOCK_VALID_RESERVED | BLOCK_VALID_TREE | BLOCK_VALID_TRANSACTIONS |
                                 BLOCK_VALID_CHAIN | BLOCK_VALID_SCRIPTS,

    BLOCK_HAVE_DATA          =    8, 
    BLOCK_HAVE_UNDO          =   16, 
    BLOCK_HAVE_MASK          =   BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO,

    BLOCK_FAILED_VALID       =   32, 
    BLOCK_FAILED_CHILD       =   64, 

    BLOCK_OPT_WITNESS        =   128, 

    BLOCK_STATUS_RESERVED    =   256, 
};

class CBlockIndex
{
public:
    const uint256* phashBlock{nullptr};

    CBlockIndex* pprev{nullptr};

    CBlockIndex* pskip{nullptr};

    int nHeight{0};

    int nFile GUARDED_BY(::cs_main){0};

    unsigned int nDataPos GUARDED_BY(::cs_main){0};

    unsigned int nUndoPos GUARDED_BY(::cs_main){0};

    arith_uint256 nChainWork{};

    unsigned int nTx{0};

    uint64_t m_chain_tx_count{0};

    uint32_t nStatus GUARDED_BY(::cs_main){0};

    int32_t nVersion{0};
    uint256 hashMerkleRoot{};
    uint32_t nTime{0};
    uint32_t nBits{0};
    uint32_t nNonce{0};

    int32_t nSequenceId{SEQ_ID_INIT_FROM_DISK};

    unsigned int nTimeMax{0};

    explicit CBlockIndex(const CBlockHeader& block)
        : nVersion{block.nVersion},
          hashMerkleRoot{block.hashMerkleRoot},
          nTime{block.nTime},
          nBits{block.nBits},
          nNonce{block.nNonce}
    {
    }

    FlatFilePos GetBlockPos() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        FlatFilePos ret;
        if (nStatus & BLOCK_HAVE_DATA) {
            ret.nFile = nFile;
            ret.nPos = nDataPos;
        }
        return ret;
    }

    FlatFilePos GetUndoPos() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        FlatFilePos ret;
        if (nStatus & BLOCK_HAVE_UNDO) {
            ret.nFile = nFile;
            ret.nPos = nUndoPos;
        }
        return ret;
    }

    CBlockHeader GetBlockHeader() const
    {
        CBlockHeader block;
        block.nVersion = nVersion;
        if (pprev)
            block.hashPrevBlock = pprev->GetBlockHash();
        block.hashMerkleRoot = hashMerkleRoot;
        block.nTime = nTime;
        block.nBits = nBits;
        block.nNonce = nNonce;
        return block;
    }

    uint256 GetBlockHash() const
    {
        assert(phashBlock != nullptr);
        return *phashBlock;
    }

    bool HaveNumChainTxs() const { return m_chain_tx_count != 0; }

    NodeSeconds Time() const
    {
        return NodeSeconds{std::chrono::seconds{nTime}};
    }

    int64_t GetBlockTime() const
    {
        return (int64_t)nTime;
    }

    int64_t GetBlockTimeMax() const
    {
        return (int64_t)nTimeMax;
    }

    static constexpr int nMedianTimeSpan = 11;

    int64_t GetMedianTimePast() const
    {
        int64_t pmedian[nMedianTimeSpan];
        int64_t* pbegin = &pmedian[nMedianTimeSpan];
        int64_t* pend = &pmedian[nMedianTimeSpan];

        const CBlockIndex* pindex = this;
        for (int i = 0; i < nMedianTimeSpan && pindex; i++, pindex = pindex->pprev)
            *(--pbegin) = pindex->GetBlockTime();

        std::sort(pbegin, pend);
        return pbegin[(pend - pbegin) / 2];
    }

    std::string ToString() const;

    bool IsValid(enum BlockStatus nUpTo) const
        EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.
        if (nStatus & BLOCK_FAILED_VALID)
            return false;
        return ((nStatus & BLOCK_VALID_MASK) >= nUpTo);
    }

    bool RaiseValidity(enum BlockStatus nUpTo) EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.
        if (nStatus & BLOCK_FAILED_VALID) return false;

        if ((nStatus & BLOCK_VALID_MASK) < nUpTo) {
            nStatus = (nStatus & ~BLOCK_VALID_MASK) | nUpTo;
            return true;
        }
        return false;
    }

    void BuildSkip();

    CBlockIndex* GetAncestor(int height);
    const CBlockIndex* GetAncestor(int height) const;

    CBlockIndex() = default;
    ~CBlockIndex() = default;

protected:
    CBlockIndex(const CBlockIndex&) = default;
    CBlockIndex& operator=(const CBlockIndex&) = delete;
    CBlockIndex(CBlockIndex&&) = delete;
    CBlockIndex& operator=(CBlockIndex&&) = delete;
};

arith_uint256 GetBitsProof(uint32_t bits);

inline arith_uint256 GetBlockProof(const CBlockIndex& block) { return GetBitsProof(block.nBits); }

inline arith_uint256 GetBlockProof(const CBlockHeader& header) { return GetBitsProof(header.nBits); }

int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params&);
const CBlockIndex* LastCommonAncestor(const CBlockIndex* pa, const CBlockIndex* pb);


class CDiskBlockIndex : public CBlockIndex
{
    static constexpr int DUMMY_VERSION = 259900;

public:
    uint256 hashPrev;

    CDiskBlockIndex()
    {
        hashPrev = uint256();
    }

    explicit CDiskBlockIndex(const CBlockIndex* pindex) : CBlockIndex(*pindex)
    {
        hashPrev = (pprev ? pprev->GetBlockHash() : uint256());
    }

    SERIALIZE_METHODS(CDiskBlockIndex, obj)
    {
        LOCK(::cs_main);
        int _nVersion = DUMMY_VERSION;
        READWRITE(VARINT_MODE(_nVersion, VarIntMode::NONNEGATIVE_SIGNED));

        READWRITE(VARINT_MODE(obj.nHeight, VarIntMode::NONNEGATIVE_SIGNED));
        READWRITE(VARINT(obj.nStatus));
        READWRITE(VARINT(obj.nTx));
        if (obj.nStatus & (BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO)) READWRITE(VARINT_MODE(obj.nFile, VarIntMode::NONNEGATIVE_SIGNED));
        if (obj.nStatus & BLOCK_HAVE_DATA) READWRITE(VARINT(obj.nDataPos));
        if (obj.nStatus & BLOCK_HAVE_UNDO) READWRITE(VARINT(obj.nUndoPos));

        // block header
        READWRITE(obj.nVersion);
        READWRITE(obj.hashPrev);
        READWRITE(obj.hashMerkleRoot);
        READWRITE(obj.nTime);
        READWRITE(obj.nBits);
        READWRITE(obj.nNonce);
    }

    uint256 ConstructBlockHash() const
    {
        CBlockHeader block;
        block.nVersion = nVersion;
        block.hashPrevBlock = hashPrev;
        block.hashMerkleRoot = hashMerkleRoot;
        block.nTime = nTime;
        block.nBits = nBits;
        block.nNonce = nNonce;
        return block.GetHash();
    }

    uint256 GetBlockHash() = delete;
    std::string ToString() = delete;
};

class CChain
{
private:
    std::vector<CBlockIndex*> vChain;

public:
    CChain() = default;
    CChain(const CChain&) = delete;
    CChain& operator=(const CChain&) = delete;

    CBlockIndex* Genesis() const
    {
        return vChain.size() > 0 ? vChain[0] : nullptr;
    }

    CBlockIndex* Tip() const
    {
        return vChain.size() > 0 ? vChain[vChain.size() - 1] : nullptr;
    }

    CBlockIndex* operator[](int nHeight) const
    {
        if (nHeight < 0 || nHeight >= (int)vChain.size())
            return nullptr;
        return vChain[nHeight];
    }

    bool Contains(const CBlockIndex* pindex) const
    {
        return (*this)[pindex->nHeight] == pindex;
    }

    CBlockIndex* Next(const CBlockIndex* pindex) const
    {
        if (Contains(pindex))
            return (*this)[pindex->nHeight + 1];
        else
            return nullptr;
    }

    int Height() const
    {
        return int(vChain.size()) - 1;
    }

    bool IsTipRecent(const arith_uint256& min_chain_work, std::chrono::seconds max_tip_age) const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        const auto tip{Tip()};
        return tip &&
               tip->nChainWork >= min_chain_work &&
               tip->Time() >= Now<NodeSeconds>() - max_tip_age;
    }

    void SetTip(CBlockIndex& block);

    const CBlockIndex* FindFork(const CBlockIndex* pindex) const;

    CBlockIndex* FindEarliestAtLeast(int64_t nTime, int height) const;
};

CBlockLocator GetLocator(const CBlockIndex* index);

std::vector<uint256> LocatorEntries(const CBlockIndex* index);

#endif // BITCOIN_CHAIN_H