src/main.h

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2013 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_MAIN_H
#define BITCOIN_MAIN_H

#if defined(HAVE_CONFIG_H)
#include "bitcoin-config.h"
#endif

#include "bignum.h"
#include "chainparams.h"
#include "coins.h"
#include "core.h"
#include "net.h"
#include "script.h"
#include "sync.h"
#include "txmempool.h"
#include "uint256.h"

#include <algorithm>
#include <exception>
#include <map>
#include <set>
#include <stdint.h>
#include <string>
#include <utility>
#include <vector>

class CBlockIndex;
class CBloomFilter;
class CInv;

/** The maximum allowed size for a serialized block, in bytes (network rule) */
static const unsigned int MAX_BLOCK_SIZE = 1000000;
/** Default for -blockmaxsize, maximum size for mined blocks **/
static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
/** Default for -blockprioritysize, maximum space for zero/low-fee transactions **/
static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 50000;
/** The maximum size for transactions we're willing to relay/mine */
static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
/** The maximum allowed number of signature check operations in a block (network rule) */
static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
/** The maximum number of orphan transactions kept in memory */
static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100;
/** The maximum size of a blk?????.dat file (since 0.8) */
static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB
/** The pre-allocation chunk size for blk?????.dat files (since 0.8) */
static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB
/** The pre-allocation chunk size for rev?????.dat files (since 0.8) */
static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB
/** Coinbase transaction outputs can only be spent after this number of new blocks (network rule) */
static const int COINBASE_MATURITY = 100;
/** Threshold for nLockTime: below this value it is interpreted as block number, otherwise as UNIX timestamp. */
static const unsigned int LOCKTIME_THRESHOLD = 500000000; // Tue Nov  5 00:53:20 1985 UTC
/** Maximum number of script-checking threads allowed */
static const int MAX_SCRIPTCHECK_THREADS = 16;
#ifdef USE_UPNP
static const int fHaveUPnP = true;
#else
static const int fHaveUPnP = false;
#endif

/** "reject" message codes **/
static const unsigned char REJECT_MALFORMED = 0x01;
static const unsigned char REJECT_INVALID = 0x10;
static const unsigned char REJECT_OBSOLETE = 0x11;
static const unsigned char REJECT_DUPLICATE = 0x12;
static const unsigned char REJECT_NONSTANDARD = 0x40;
static const unsigned char REJECT_DUST = 0x41;
static const unsigned char REJECT_INSUFFICIENTFEE = 0x42;
static const unsigned char REJECT_CHECKPOINT = 0x43;


extern CScript COINBASE_FLAGS;


extern CCriticalSection cs_main;
extern CTxMemPool mempool;
extern std::map<uint256, CBlockIndex*> mapBlockIndex;
extern uint64_t nLastBlockTx;
extern uint64_t nLastBlockSize;
extern const std::string strMessageMagic;
extern int64_t nTimeBestReceived;
extern bool fImporting;
extern bool fReindex;
extern bool fBenchmark;
extern int nScriptCheckThreads;
extern bool fTxIndex;
extern unsigned int nCoinCacheSize;
extern bool fHaveGUI;

// Minimum disk space required - used in CheckDiskSpace()
static const uint64_t nMinDiskSpace = 52428800;


class CCoinsDB;
class CBlockTreeDB;
struct CDiskBlockPos;
class CTxUndo;
class CScriptCheck;
class CValidationState;
class CWalletInterface;
struct CNodeStateStats;

struct CBlockTemplate;

/** Register a wallet to receive updates from core */
void RegisterWallet(CWalletInterface* pwalletIn);
/** Unregister a wallet from core */
void UnregisterWallet(CWalletInterface* pwalletIn);
/** Unregister all wallets from core */
void UnregisterAllWallets();
/** Push an updated transaction to all registered wallets */
void SyncWithWallets(const uint256 &hash, const CTransaction& tx, const CBlock* pblock = NULL);

/** Register with a network node to receive its signals */
void RegisterNodeSignals(CNodeSignals& nodeSignals);
/** Unregister a network node */
void UnregisterNodeSignals(CNodeSignals& nodeSignals);

void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd);

/** Process an incoming block */
bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp = NULL);
/** Check whether enough disk space is available for an incoming block */
bool CheckDiskSpace(uint64_t nAdditionalBytes = 0);
/** Open a block file (blk?????.dat) */
FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly = false);
/** Open an undo file (rev?????.dat) */
FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
/** Import blocks from an external file */
bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp = NULL);
/** Initialize a new block tree database + block data on disk */
bool InitBlockIndex();
/** Load the block tree and coins database from disk */
bool LoadBlockIndex();
/** Unload database information */
void UnloadBlockIndex();
/** Verify consistency of the block and coin databases */
bool VerifyDB(int nCheckLevel, int nCheckDepth);
/** Print the loaded block tree */
void PrintBlockTree();
/** Process protocol messages received from a given node */
bool ProcessMessages(CNode* pfrom);
/** Send queued protocol messages to be sent to a give node */
bool SendMessages(CNode* pto, bool fSendTrickle);
/** Run an instance of the script checking thread */
void ThreadScriptCheck();
/** Check whether a block hash satisfies the proof-of-work requirement specified by nBits */
bool CheckProofOfWork(uint256 hash, unsigned int nBits);
/** Calculate the minimum amount of work a received block needs, without knowing its direct parent */
unsigned int ComputeMinWork(unsigned int nBase, int64_t nTime);
/** Get the number of active peers */
int GetNumBlocksOfPeers();
/** Check whether we are doing an initial block download (synchronizing from disk or network) */
bool IsInitialBlockDownload();
/** Format a string that describes several potential problems detected by the core */
std::string GetWarnings(std::string strFor);
/** Retrieve a transaction (from memory pool, or from disk, if possible) */
bool GetTransaction(const uint256 &hash, CTransaction &tx, uint256 &hashBlock, bool fAllowSlow = false);
/** Connect/disconnect blocks until pindexNew is the new tip of the active block chain */
bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew);
/** Find the best known block, and make it the tip of the block chain */
bool ConnectBestBlock(CValidationState &state);
int64_t GetBlockValue(int nHeight, int64_t nFees);
unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock);

void UpdateTime(CBlockHeader& block, const CBlockIndex* pindexPrev);

/** Create a new block index entry for a given block hash */
CBlockIndex * InsertBlockIndex(uint256 hash);
/** Verify a signature */
bool VerifySignature(const CCoins& txFrom, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);
/** Abort with a message */
bool AbortNode(const std::string &msg);
/** Get statistics from node state */
bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats);

/** (try to) add transaction to memory pool **/
bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                        bool* pfMissingInputs, bool fRejectInsaneFee=false);


struct CNodeStateStats {
    int nMisbehavior;
};

struct CDiskBlockPos
{
    int nFile;
    unsigned int nPos;

    IMPLEMENT_SERIALIZE(
        READWRITE(VARINT(nFile));
        READWRITE(VARINT(nPos));
    )

    CDiskBlockPos() {
        SetNull();
    }

    CDiskBlockPos(int nFileIn, unsigned int nPosIn) {
        nFile = nFileIn;
        nPos = nPosIn;
    }

    friend bool operator==(const CDiskBlockPos &a, const CDiskBlockPos &b) {
        return (a.nFile == b.nFile && a.nPos == b.nPos);
    }

    friend bool operator!=(const CDiskBlockPos &a, const CDiskBlockPos &b) {
        return !(a == b);
    }

    void SetNull() { nFile = -1; nPos = 0; }
    bool IsNull() const { return (nFile == -1); }
};

struct CDiskTxPos : public CDiskBlockPos
{
    unsigned int nTxOffset; // after header

    IMPLEMENT_SERIALIZE(
        READWRITE(*(CDiskBlockPos*)this);
        READWRITE(VARINT(nTxOffset));
    )

    CDiskTxPos(const CDiskBlockPos &blockIn, unsigned int nTxOffsetIn) : CDiskBlockPos(blockIn.nFile, blockIn.nPos), nTxOffset(nTxOffsetIn) {
    }

    CDiskTxPos() {
        SetNull();
    }

    void SetNull() {
        CDiskBlockPos::SetNull();
        nTxOffset = 0;
    }
};


enum GetMinFee_mode
{
    GMF_RELAY,
    GMF_SEND,
};

int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree, enum GetMinFee_mode mode);

//
// Check transaction inputs, and make sure any
// pay-to-script-hash transactions are evaluating IsStandard scripts
//
// Why bother? To avoid denial-of-service attacks; an attacker
// can submit a standard HASH... OP_EQUAL transaction,
// which will get accepted into blocks. The redemption
// script can be anything; an attacker could use a very
// expensive-to-check-upon-redemption script like:
//   DUP CHECKSIG DROP ... repeated 100 times... OP_1
//

    /** Check for standard transaction types
        @param[in] mapInputs    Map of previous transactions that have outputs we're spending
        @return True if all inputs (scriptSigs) use only standard transaction forms
    */
bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs);

/** Count ECDSA signature operations the old-fashioned (pre-0.6) way
    @return number of sigops this transaction's outputs will produce when spent
    @see CTransaction::FetchInputs
*/
unsigned int GetLegacySigOpCount(const CTransaction& tx);

/** Count ECDSA signature operations in pay-to-script-hash inputs.

    @param[in] mapInputs	Map of previous transactions that have outputs we're spending
    @return maximum number of sigops required to validate this transaction's inputs
    @see CTransaction::FetchInputs
 */
unsigned int GetP2SHSigOpCount(const CTransaction& tx, CCoinsViewCache& mapInputs);


inline bool AllowFree(double dPriority)
{
    // Large (in bytes) low-priority (new, small-coin) transactions
    // need a fee.
    return dPriority > COIN * 144 / 250;
}

// Check whether all inputs of this transaction are valid (no double spends, scripts & sigs, amounts)
// This does not modify the UTXO set. If pvChecks is not NULL, script checks are pushed onto it
// instead of being performed inline.
bool CheckInputs(const CTransaction& tx, CValidationState &state, CCoinsViewCache &view, bool fScriptChecks = true,
                 unsigned int flags = SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC,
                 std::vector<CScriptCheck> *pvChecks = NULL);

// Apply the effects of this transaction on the UTXO set represented by view
void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, CTxUndo &txundo, int nHeight, const uint256 &txhash);

// Context-independent validity checks
bool CheckTransaction(const CTransaction& tx, CValidationState& state);

/** Check for standard transaction types
    @return True if all outputs (scriptPubKeys) use only standard transaction forms
*/
bool IsStandardTx(const CTransaction& tx, std::string& reason);

bool IsFinalTx(const CTransaction &tx, int nBlockHeight = 0, int64_t nBlockTime = 0);

/** Undo information for a CBlock */
class CBlockUndo
{
public:
    std::vector<CTxUndo> vtxundo; // for all but the coinbase

    IMPLEMENT_SERIALIZE(
        READWRITE(vtxundo);
    )

    bool WriteToDisk(CDiskBlockPos &pos, const uint256 &hashBlock)
    {
        // Open history file to append
        CAutoFile fileout = CAutoFile(OpenUndoFile(pos), SER_DISK, CLIENT_VERSION);
        if (!fileout)
            return error("CBlockUndo::WriteToDisk : OpenUndoFile failed");

        // Write index header
        unsigned int nSize = fileout.GetSerializeSize(*this);
        fileout << FLATDATA(Params().MessageStart()) << nSize;

        // Write undo data
        long fileOutPos = ftell(fileout);
        if (fileOutPos < 0)
            return error("CBlockUndo::WriteToDisk : ftell failed");
        pos.nPos = (unsigned int)fileOutPos;
        fileout << *this;

        // calculate & write checksum
        CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
        hasher << hashBlock;
        hasher << *this;
        fileout << hasher.GetHash();

        // Flush stdio buffers and commit to disk before returning
        fflush(fileout);
        if (!IsInitialBlockDownload())
            FileCommit(fileout);

        return true;
    }

    bool ReadFromDisk(const CDiskBlockPos &pos, const uint256 &hashBlock)
    {
        // Open history file to read
        CAutoFile filein = CAutoFile(OpenUndoFile(pos, true), SER_DISK, CLIENT_VERSION);
        if (!filein)
            return error("CBlockUndo::ReadFromDisk : OpenBlockFile failed");

        // Read block
        uint256 hashChecksum;
        try {
            filein >> *this;
            filein >> hashChecksum;
        }
        catch (std::exception &e) {
            return error("%s : Deserialize or I/O error - %s", __PRETTY_FUNCTION__, e.what());
        }

        // Verify checksum
        CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
        hasher << hashBlock;
        hasher << *this;
        if (hashChecksum != hasher.GetHash())
            return error("CBlockUndo::ReadFromDisk : Checksum mismatch");

        return true;
    }
};


/** Closure representing one script verification
 *  Note that this stores references to the spending transaction */
class CScriptCheck
{
private:
    CScript scriptPubKey;
    const CTransaction *ptxTo;
    unsigned int nIn;
    unsigned int nFlags;
    int nHashType;

public:
    CScriptCheck() {}
    CScriptCheck(const CCoins& txFromIn, const CTransaction& txToIn, unsigned int nInIn, unsigned int nFlagsIn, int nHashTypeIn) :
        scriptPubKey(txFromIn.vout[txToIn.vin[nInIn].prevout.n].scriptPubKey),
        ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), nHashType(nHashTypeIn) { }

    bool operator()() const;

    void swap(CScriptCheck &check) {
        scriptPubKey.swap(check.scriptPubKey);
        std::swap(ptxTo, check.ptxTo);
        std::swap(nIn, check.nIn);
        std::swap(nFlags, check.nFlags);
        std::swap(nHashType, check.nHashType);
    }
};

/** A transaction with a merkle branch linking it to the block chain. */
class CMerkleTx : public CTransaction
{
public:
    uint256 hashBlock;
    std::vector<uint256> vMerkleBranch;
    int nIndex;

    // memory only
    mutable bool fMerkleVerified;


    CMerkleTx()
    {
        Init();
    }

    CMerkleTx(const CTransaction& txIn) : CTransaction(txIn)
    {
        Init();
    }

    void Init()
    {
        hashBlock = 0;
        nIndex = -1;
        fMerkleVerified = false;
    }


    IMPLEMENT_SERIALIZE
    (
        nSerSize += SerReadWrite(s, *(CTransaction*)this, nType, nVersion, ser_action);
        nVersion = this->nVersion;
        READWRITE(hashBlock);
        READWRITE(vMerkleBranch);
        READWRITE(nIndex);
    )


    int SetMerkleBranch(const CBlock* pblock=NULL);
    int GetDepthInMainChain(CBlockIndex* &pindexRet) const;
    int GetDepthInMainChain() const { CBlockIndex *pindexRet; return GetDepthInMainChain(pindexRet); }
    bool IsInMainChain() const { return GetDepthInMainChain() > 0; }
    int GetBlocksToMaturity() const;
    bool AcceptToMemoryPool(bool fLimitFree=true);
};


/** Data structure that represents a partial merkle tree.
 *
 * It respresents a subset of the txid's of a known block, in a way that
 * allows recovery of the list of txid's and the merkle root, in an
 * authenticated way.
 *
 * The encoding works as follows: we traverse the tree in depth-first order,
 * storing a bit for each traversed node, signifying whether the node is the
 * parent of at least one matched leaf txid (or a matched txid itself). In
 * case we are at the leaf level, or this bit is 0, its merkle node hash is
 * stored, and its children are not explorer further. Otherwise, no hash is
 * stored, but we recurse into both (or the only) child branch. During
 * decoding, the same depth-first traversal is performed, consuming bits and
 * hashes as they written during encoding.
 *
 * The serialization is fixed and provides a hard guarantee about the
 * encoded size:
 *
 *   SIZE <= 10 + ceil(32.25*N)
 *
 * Where N represents the number of leaf nodes of the partial tree. N itself
 * is bounded by:
 *
 *   N <= total_transactions
 *   N <= 1 + matched_transactions*tree_height
 *
 * The serialization format:
 *  - uint32     total_transactions (4 bytes)
 *  - varint     number of hashes   (1-3 bytes)
 *  - uint256[]  hashes in depth-first order (<= 32*N bytes)
 *  - varint     number of bytes of flag bits (1-3 bytes)
 *  - byte[]     flag bits, packed per 8 in a byte, least significant bit first (<= 2*N-1 bits)
 * The size constraints follow from this.
 */
class CPartialMerkleTree
{
protected:
    // the total number of transactions in the block
    unsigned int nTransactions;

    // node-is-parent-of-matched-txid bits
    std::vector<bool> vBits;

    // txids and internal hashes
    std::vector<uint256> vHash;

    // flag set when encountering invalid data
    bool fBad;

    // helper function to efficiently calculate the number of nodes at given height in the merkle tree
    unsigned int CalcTreeWidth(int height) {
        return (nTransactions+(1 << height)-1) >> height;
    }

    // calculate the hash of a node in the merkle tree (at leaf level: the txid's themself)
    uint256 CalcHash(int height, unsigned int pos, const std::vector<uint256> &vTxid);

    // recursive function that traverses tree nodes, storing the data as bits and hashes
    void TraverseAndBuild(int height, unsigned int pos, const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch);

    // recursive function that traverses tree nodes, consuming the bits and hashes produced by TraverseAndBuild.
    // it returns the hash of the respective node.
    uint256 TraverseAndExtract(int height, unsigned int pos, unsigned int &nBitsUsed, unsigned int &nHashUsed, std::vector<uint256> &vMatch);

public:

    // serialization implementation
    IMPLEMENT_SERIALIZE(
        READWRITE(nTransactions);
        READWRITE(vHash);
        std::vector<unsigned char> vBytes;
        if (fRead) {
            READWRITE(vBytes);
            CPartialMerkleTree &us = *(const_cast<CPartialMerkleTree*>(this));
            us.vBits.resize(vBytes.size() * 8);
            for (unsigned int p = 0; p < us.vBits.size(); p++)
                us.vBits[p] = (vBytes[p / 8] & (1 << (p % 8))) != 0;
            us.fBad = false;
        } else {
            vBytes.resize((vBits.size()+7)/8);
            for (unsigned int p = 0; p < vBits.size(); p++)
                vBytes[p / 8] |= vBits[p] << (p % 8);
            READWRITE(vBytes);
        }
    )

    // Construct a partial merkle tree from a list of transaction id's, and a mask that selects a subset of them
    CPartialMerkleTree(const std::vector<uint256> &vTxid, const std::vector<bool> &vMatch);

    CPartialMerkleTree();

    // extract the matching txid's represented by this partial merkle tree.
    // returns the merkle root, or 0 in case of failure
    uint256 ExtractMatches(std::vector<uint256> &vMatch);
};


/** Functions for disk access for blocks */
bool WriteBlockToDisk(CBlock& block, CDiskBlockPos& pos);
bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos);
bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex);


/** Functions for validating blocks and updating the block tree */

/** Undo the effects of this block (with given index) on the UTXO set represented by coins.
 *  In case pfClean is provided, operation will try to be tolerant about errors, and *pfClean
 *  will be true if no problems were found. Otherwise, the return value will be false in case
 *  of problems. Note that in any case, coins may be modified. */
bool DisconnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, CCoinsViewCache& coins, bool* pfClean = NULL);

// Apply the effects of this block (with given index) on the UTXO set represented by coins
bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, CCoinsViewCache& coins, bool fJustCheck = false);

// Add this block to the block index, and if necessary, switch the active block chain to this
bool AddToBlockIndex(CBlock& block, CValidationState& state, const CDiskBlockPos& pos);

// Context-independent validity checks
bool CheckBlock(const CBlock& block, CValidationState& state, bool fCheckPOW = true, bool fCheckMerkleRoot = true);

// Store block on disk
// if dbp is provided, the file is known to already reside on disk
bool AcceptBlock(CBlock& block, CValidationState& state, CDiskBlockPos* dbp = NULL);


class CBlockFileInfo
{
public:
    unsigned int nBlocks;      // number of blocks stored in file
    unsigned int nSize;        // number of used bytes of block file
    unsigned int nUndoSize;    // number of used bytes in the undo file
    unsigned int nHeightFirst; // lowest height of block in file
    unsigned int nHeightLast;  // highest height of block in file
    uint64_t nTimeFirst;         // earliest time of block in file
    uint64_t nTimeLast;          // latest time of block in file

    IMPLEMENT_SERIALIZE(
        READWRITE(VARINT(nBlocks));
        READWRITE(VARINT(nSize));
        READWRITE(VARINT(nUndoSize));
        READWRITE(VARINT(nHeightFirst));
        READWRITE(VARINT(nHeightLast));
        READWRITE(VARINT(nTimeFirst));
        READWRITE(VARINT(nTimeLast));
     )

     void SetNull() {
         nBlocks = 0;
         nSize = 0;
         nUndoSize = 0;
         nHeightFirst = 0;
         nHeightLast = 0;
         nTimeFirst = 0;
         nTimeLast = 0;
     }

     CBlockFileInfo() {
         SetNull();
     }

     std::string ToString() const {
         return strprintf("CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)", nBlocks, nSize, nHeightFirst, nHeightLast, DateTimeStrFormat("%Y-%m-%d", nTimeFirst).c_str(), DateTimeStrFormat("%Y-%m-%d", nTimeLast).c_str());
     }

     // update statistics (does not update nSize)
     void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn) {
         if (nBlocks==0 || nHeightFirst > nHeightIn)
             nHeightFirst = nHeightIn;
         if (nBlocks==0 || nTimeFirst > nTimeIn)
             nTimeFirst = nTimeIn;
         nBlocks++;
         if (nHeightIn > nHeightLast)
             nHeightLast = nHeightIn;
         if (nTimeIn > nTimeLast)
             nTimeLast = nTimeIn;
     }
};

enum BlockStatus {
    BLOCK_VALID_UNKNOWN      =    0,
    BLOCK_VALID_HEADER       =    1, // parsed, version ok, hash satisfies claimed PoW, 1 <= vtx count <= max, timestamp not in future
    BLOCK_VALID_TREE         =    2, // parent found, difficulty matches, timestamp >= median previous, checkpoint
    BLOCK_VALID_TRANSACTIONS =    3, // only first tx is coinbase, 2 <= coinbase input script length <= 100, transactions valid, no duplicate txids, sigops, size, merkle root
    BLOCK_VALID_CHAIN        =    4, // outputs do not overspend inputs, no double spends, coinbase output ok, immature coinbase spends, BIP30
    BLOCK_VALID_SCRIPTS      =    5, // scripts/signatures ok
    BLOCK_VALID_MASK         =    7,

    BLOCK_HAVE_DATA          =    8, // full block available in blk*.dat
    BLOCK_HAVE_UNDO          =   16, // undo data available in rev*.dat
    BLOCK_HAVE_MASK          =   24,

    BLOCK_FAILED_VALID       =   32, // stage after last reached validness failed
    BLOCK_FAILED_CHILD       =   64, // descends from failed block
    BLOCK_FAILED_MASK        =   96
};

/** The block chain is a tree shaped structure starting with the
 * genesis block at the root, with each block potentially having multiple
 * candidates to be the next block. A blockindex may have multiple pprev pointing
 * to it, but at most one of them can be part of the currently active branch.
 */
class CBlockIndex
{
public:
    // pointer to the hash of the block, if any. memory is owned by this CBlockIndex
    const uint256* phashBlock;

    // pointer to the index of the predecessor of this block
    CBlockIndex* pprev;

    // height of the entry in the chain. The genesis block has height 0
    int nHeight;

    // Which # file this block is stored in (blk?????.dat)
    int nFile;

    // Byte offset within blk?????.dat where this block's data is stored
    unsigned int nDataPos;

    // Byte offset within rev?????.dat where this block's undo data is stored
    unsigned int nUndoPos;

    // (memory only) Total amount of work (expected number of hashes) in the chain up to and including this block
    uint256 nChainWork;

    // Number of transactions in this block.
    // Note: in a potential headers-first mode, this number cannot be relied upon
    unsigned int nTx;

    // (memory only) Number of transactions in the chain up to and including this block
    unsigned int nChainTx; // change to 64-bit type when necessary; won't happen before 2030

    // Verification status of this block. See enum BlockStatus
    unsigned int nStatus;

    // block header
    int nVersion;
    uint256 hashMerkleRoot;
    unsigned int nTime;
    unsigned int nBits;
    unsigned int nNonce;


    CBlockIndex()
    {
        phashBlock = NULL;
        pprev = NULL;
        nHeight = 0;
        nFile = 0;
        nDataPos = 0;
        nUndoPos = 0;
        nChainWork = 0;
        nTx = 0;
        nChainTx = 0;
        nStatus = 0;

        nVersion       = 0;
        hashMerkleRoot = 0;
        nTime          = 0;
        nBits          = 0;
        nNonce         = 0;
    }

    CBlockIndex(CBlockHeader& block)
    {
        phashBlock = NULL;
        pprev = NULL;
        nHeight = 0;
        nFile = 0;
        nDataPos = 0;
        nUndoPos = 0;
        nChainWork = 0;
        nTx = 0;
        nChainTx = 0;
        nStatus = 0;

        nVersion       = block.nVersion;
        hashMerkleRoot = block.hashMerkleRoot;
        nTime          = block.nTime;
        nBits          = block.nBits;
        nNonce         = block.nNonce;
    }

    CDiskBlockPos GetBlockPos() const {
        CDiskBlockPos ret;
        if (nStatus & BLOCK_HAVE_DATA) {
            ret.nFile = nFile;
            ret.nPos  = nDataPos;
        }
        return ret;
    }

    CDiskBlockPos GetUndoPos() const {
        CDiskBlockPos 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
    {
        return *phashBlock;
    }

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

    CBigNum GetBlockWork() const
    {
        CBigNum bnTarget;
        bnTarget.SetCompact(nBits);
        if (bnTarget <= 0)
            return 0;
        return (CBigNum(1)<<256) / (bnTarget+1);
    }

    bool CheckIndex() const
    {
        return CheckProofOfWork(GetBlockHash(), nBits);
    }

    enum { 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];
    }

    int64_t GetMedianTime() const;

    /**
     * Returns true if there are nRequired or more blocks of minVersion or above
     * in the last nToCheck blocks, starting at pstart and going backwards.
     */
    static bool IsSuperMajority(int minVersion, const CBlockIndex* pstart,
                                unsigned int nRequired, unsigned int nToCheck);

    std::string ToString() const
    {
        return strprintf("CBlockIndex(pprev=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
            pprev, nHeight,
            hashMerkleRoot.ToString().c_str(),
            GetBlockHash().ToString().c_str());
    }

    void print() const
    {
        LogPrintf("%s\n", ToString().c_str());
    }
};


/** Used to marshal pointers into hashes for db storage. */
class CDiskBlockIndex : public CBlockIndex
{
public:
    uint256 hashPrev;

    CDiskBlockIndex() {
        hashPrev = 0;
    }

    explicit CDiskBlockIndex(CBlockIndex* pindex) : CBlockIndex(*pindex) {
        hashPrev = (pprev ? pprev->GetBlockHash() : 0);
    }

    IMPLEMENT_SERIALIZE
    (
        if (!(nType & SER_GETHASH))
            READWRITE(VARINT(nVersion));

        READWRITE(VARINT(nHeight));
        READWRITE(VARINT(nStatus));
        READWRITE(VARINT(nTx));
        if (nStatus & (BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO))
            READWRITE(VARINT(nFile));
        if (nStatus & BLOCK_HAVE_DATA)
            READWRITE(VARINT(nDataPos));
        if (nStatus & BLOCK_HAVE_UNDO)
            READWRITE(VARINT(nUndoPos));

        // block header
        READWRITE(this->nVersion);
        READWRITE(hashPrev);
        READWRITE(hashMerkleRoot);
        READWRITE(nTime);
        READWRITE(nBits);
        READWRITE(nNonce);
    )

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


    std::string ToString() const
    {
        std::string str = "CDiskBlockIndex(";
        str += CBlockIndex::ToString();
        str += strprintf("\n                hashBlock=%s, hashPrev=%s)",
            GetBlockHash().ToString().c_str(),
            hashPrev.ToString().c_str());
        return str;
    }

    void print() const
    {
        LogPrintf("%s\n", ToString().c_str());
    }
};

/** Capture information about block/transaction validation */
class CValidationState {
private:
    enum mode_state {
        MODE_VALID,   // everything ok
        MODE_INVALID, // network rule violation (DoS value may be set)
        MODE_ERROR,   // run-time error
    } mode;
    int nDoS;
    std::string strRejectReason;
    unsigned char chRejectCode;
    bool corruptionPossible;
public:
    CValidationState() : mode(MODE_VALID), nDoS(0), corruptionPossible(false) {}
    bool DoS(int level, bool ret = false,
             unsigned char chRejectCodeIn=0, std::string strRejectReasonIn="",
             bool corruptionIn=false) {
        chRejectCode = chRejectCodeIn;
        strRejectReason = strRejectReasonIn;
        corruptionPossible = corruptionIn;
        if (mode == MODE_ERROR)
            return ret;
        nDoS += level;
        mode = MODE_INVALID;
        return ret;
    }
    bool Invalid(bool ret = false,
                 unsigned char _chRejectCode=0, std::string _strRejectReason="") {
        return DoS(0, ret, _chRejectCode, _strRejectReason);
    }
    bool Error() {
        mode = MODE_ERROR;
        return false;
    }
    bool Abort(const std::string &msg) {
        AbortNode(msg);
        return Error();
    }
    bool IsValid() {
        return mode == MODE_VALID;
    }
    bool IsInvalid() {
        return mode == MODE_INVALID;
    }
    bool IsError() {
        return mode == MODE_ERROR;
    }
    bool IsInvalid(int &nDoSOut) {
        if (IsInvalid()) {
            nDoSOut = nDoS;
            return true;
        }
        return false;
    }
    bool CorruptionPossible() {
        return corruptionPossible;
    }
    unsigned char GetRejectCode() const { return chRejectCode; }
    std::string GetRejectReason() const { return strRejectReason; }
};

/** An in-memory indexed chain of blocks. */
class CChain {
private:
    std::vector<CBlockIndex*> vChain;

public:
    /** Returns the index entry for the genesis block of this chain, or NULL if none. */
    CBlockIndex *Genesis() const {
        return vChain.size() > 0 ? vChain[0] : NULL;
    }

    /** Returns the index entry for the tip of this chain, or NULL if none. */
    CBlockIndex *Tip() const {
        return vChain.size() > 0 ? vChain[vChain.size() - 1] : NULL;
    }

    /** Returns the index entry at a particular height in this chain, or NULL if no such height exists. */
    CBlockIndex *operator[](int nHeight) const {
        if (nHeight < 0 || nHeight >= (int)vChain.size())
            return NULL;
        return vChain[nHeight];
    }

    /** Compare two chains efficiently. */
    friend bool operator==(const CChain &a, const CChain &b) {
        return a.vChain.size() == b.vChain.size() &&
               a.vChain[a.vChain.size() - 1] == b.vChain[b.vChain.size() - 1];
    }

    /** Efficiently check whether a block is present in this chain. */
    bool Contains(const CBlockIndex *pindex) const {
        return (*this)[pindex->nHeight] == pindex;
    }

    /** Find the successor of a block in this chain, or NULL if the given index is not found or is the tip. */
    CBlockIndex *Next(const CBlockIndex *pindex) const {
        if (Contains(pindex))
            return (*this)[pindex->nHeight + 1];
        else
            return NULL;
    }

    /** Return the maximal height in the chain. Is equal to chain.Tip() ? chain.Tip()->nHeight : -1. */
    int Height() const {
        return vChain.size() - 1;
    }

    /** Set/initialize a chain with a given tip. Returns the forking point. */
    CBlockIndex *SetTip(CBlockIndex *pindex);

    /** Return a CBlockLocator that refers to a block in this chain (by default the tip). */
    CBlockLocator GetLocator(const CBlockIndex *pindex = NULL) const;

    /** Find the last common block between this chain and a locator. */
    CBlockIndex *FindFork(const CBlockLocator &locator) const;
};

/** The currently-connected chain of blocks. */
extern CChain chainActive;


/** Global variable that points to the active CCoinsView (protected by cs_main) */
extern CCoinsViewCache *pcoinsTip;

/** Global variable that points to the active block tree (protected by cs_main) */
extern CBlockTreeDB *pblocktree;

struct CBlockTemplate
{
    CBlock block;
    std::vector<int64_t> vTxFees;
    std::vector<int64_t> vTxSigOps;
};


/** Used to relay blocks as header + vector<merkle branch>
 * to filtered nodes.
 */
class CMerkleBlock
{
public:
    // Public only for unit testing
    CBlockHeader header;
    CPartialMerkleTree txn;

public:
    // Public only for unit testing and relay testing
    // (not relayed)
    std::vector<std::pair<unsigned int, uint256> > vMatchedTxn;

    // Create from a CBlock, filtering transactions according to filter
    // Note that this will call IsRelevantAndUpdate on the filter for each transaction,
    // thus the filter will likely be modified.
    CMerkleBlock(const CBlock& block, CBloomFilter& filter);

    IMPLEMENT_SERIALIZE
    (
        READWRITE(header);
        READWRITE(txn);
    )
};


class CWalletInterface {
protected:
    virtual void SyncTransaction(const uint256 &hash, const CTransaction &tx, const CBlock *pblock) =0;
    virtual void EraseFromWallet(const uint256 &hash) =0;
    virtual void SetBestChain(const CBlockLocator &locator) =0;
    virtual void UpdatedTransaction(const uint256 &hash) =0;
    virtual void Inventory(const uint256 &hash) =0;
    virtual void ResendWalletTransactions() =0;
    friend void ::RegisterWallet(CWalletInterface*);
    friend void ::UnregisterWallet(CWalletInterface*);
    friend void ::UnregisterAllWallets();
};

#endif