litecoin/src/db.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "db.h"
#include "util.h"
#include "main.h"
#include <boost/version.hpp>
#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>

#ifndef WIN32
#include "sys/stat.h"
#endif

using namespace std;
using namespace boost;


unsigned int nWalletDBUpdated;



//
// CDB
//

CDBEnv bitdb;

void CDBEnv::EnvShutdown()
{
    if (!fDbEnvInit)
        return;

    fDbEnvInit = false;
    int ret = dbenv.close(0);
    if (ret != 0)
        printf("EnvShutdown exception: %s (%d)\n", DbEnv::strerror(ret), ret);
    if (!fMockDb)
        DbEnv(0).remove(GetDataDir().string().c_str(), 0);
}

CDBEnv::CDBEnv() : dbenv(DB_CXX_NO_EXCEPTIONS)
{
}

CDBEnv::~CDBEnv()
{
    EnvShutdown();
}

void CDBEnv::Close()
{
    EnvShutdown();
}

bool CDBEnv::Open(boost::filesystem::path pathEnv_)
{
    if (fDbEnvInit)
        return true;

    if (fShutdown)
        return false;

    pathEnv = pathEnv_;
    filesystem::path pathDataDir = pathEnv;
    filesystem::path pathLogDir = pathDataDir / "database";
    filesystem::create_directory(pathLogDir);
    filesystem::path pathErrorFile = pathDataDir / "db.log";
    printf("dbenv.open LogDir=%s ErrorFile=%s\n", pathLogDir.string().c_str(), pathErrorFile.string().c_str());

    unsigned int nEnvFlags = 0;
    if (GetBoolArg("-privdb", true))
        nEnvFlags |= DB_PRIVATE;

    int nDbCache = GetArg("-dbcache", 25);
    dbenv.set_lg_dir(pathLogDir.string().c_str());
    dbenv.set_cachesize(nDbCache / 1024, (nDbCache % 1024)*1048576, 1);
    dbenv.set_lg_bsize(1048576);
    dbenv.set_lg_max(10485760);
    dbenv.set_lk_max_locks(40000);
    dbenv.set_lk_max_objects(40000);
    dbenv.set_errfile(fopen(pathErrorFile.string().c_str(), "a")); /// debug
    dbenv.set_flags(DB_AUTO_COMMIT, 1);
    dbenv.set_flags(DB_TXN_WRITE_NOSYNC, 1);
    dbenv.log_set_config(DB_LOG_AUTO_REMOVE, 1);
    int ret = dbenv.open(pathDataDir.string().c_str(),
                     DB_CREATE     |
                     DB_INIT_LOCK  |
                     DB_INIT_LOG   |
                     DB_INIT_MPOOL |
                     DB_INIT_TXN   |
                     DB_THREAD     |
                     DB_RECOVER    |
                     nEnvFlags,
                     S_IRUSR | S_IWUSR);
    if (ret != 0)
        return error("CDB() : error %s (%d) opening database environment", DbEnv::strerror(ret), ret);

    fDbEnvInit = true;
    fMockDb = false;
    return true;
}

void CDBEnv::MakeMock()
{
    if (fDbEnvInit)
        throw runtime_error("CDBEnv::MakeMock(): already initialized");

    if (fShutdown)
        throw runtime_error("CDBEnv::MakeMock(): during shutdown");

    printf("CDBEnv::MakeMock()\n");

    dbenv.set_cachesize(1, 0, 1);
    dbenv.set_lg_bsize(10485760*4);
    dbenv.set_lg_max(10485760);
    dbenv.set_lk_max_locks(10000);
    dbenv.set_lk_max_objects(10000);
    dbenv.set_flags(DB_AUTO_COMMIT, 1);
    dbenv.log_set_config(DB_LOG_IN_MEMORY, 1);
    int ret = dbenv.open(NULL,
                     DB_CREATE     |
                     DB_INIT_LOCK  |
                     DB_INIT_LOG   |
                     DB_INIT_MPOOL |
                     DB_INIT_TXN   |
                     DB_THREAD     |
                     DB_PRIVATE,
                     S_IRUSR | S_IWUSR);
    if (ret > 0)
        throw runtime_error(strprintf("CDBEnv::MakeMock(): error %d opening database environment", ret));

    fDbEnvInit = true;
    fMockDb = true;
}

CDBEnv::VerifyResult CDBEnv::Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile))
{
    LOCK(cs_db);
    assert(mapFileUseCount.count(strFile) == 0);

    Db db(&dbenv, 0);
    int result = db.verify(strFile.c_str(), NULL, NULL, 0);
    if (result == 0)
        return VERIFY_OK;
    else if (recoverFunc == NULL)
        return RECOVER_FAIL;

    // Try to recover:
    bool fRecovered = (*recoverFunc)(*this, strFile);
    return (fRecovered ? RECOVER_OK : RECOVER_FAIL);
}

bool CDBEnv::Salvage(std::string strFile, bool fAggressive,
                     std::vector<CDBEnv::KeyValPair >& vResult)
{
    LOCK(cs_db);
    assert(mapFileUseCount.count(strFile) == 0);

    u_int32_t flags = DB_SALVAGE;
    if (fAggressive) flags |= DB_AGGRESSIVE;

    stringstream strDump;

    Db db(&dbenv, 0);
    int result = db.verify(strFile.c_str(), NULL, &strDump, flags);
    if (result != 0)
    {
        printf("ERROR: db salvage failed\n");
        return false;
    }

    // Format of bdb dump is ascii lines:
    // header lines...
    // HEADER=END
    // hexadecimal key
    // hexadecimal value
    // ... repeated
    // DATA=END

    string strLine;
    while (!strDump.eof() && strLine != "HEADER=END")
        getline(strDump, strLine); // Skip past header

    std::string keyHex, valueHex;
    while (!strDump.eof() && keyHex != "DATA=END")
    {
        getline(strDump, keyHex);
        if (keyHex != "DATA_END")
        {
            getline(strDump, valueHex);
            vResult.push_back(make_pair(ParseHex(keyHex),ParseHex(valueHex)));
        }
    }

    return (result == 0);
}


void CDBEnv::CheckpointLSN(std::string strFile)
{
    dbenv.txn_checkpoint(0, 0, 0);
    if (fMockDb)
        return;
    dbenv.lsn_reset(strFile.c_str(), 0);
}


CDB::CDB(const char *pszFile, const char* pszMode) :
    pdb(NULL), activeTxn(NULL)
{
    int ret;
    if (pszFile == NULL)
        return;

    fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
    bool fCreate = strchr(pszMode, 'c');
    unsigned int nFlags = DB_THREAD;
    if (fCreate)
        nFlags |= DB_CREATE;

    {
        LOCK(bitdb.cs_db);
        if (!bitdb.Open(GetDataDir()))
            throw runtime_error("env open failed");

        strFile = pszFile;
        ++bitdb.mapFileUseCount[strFile];
        pdb = bitdb.mapDb[strFile];
        if (pdb == NULL)
        {
            pdb = new Db(&bitdb.dbenv, 0);

            bool fMockDb = bitdb.IsMock();
            if (fMockDb)
            {
                DbMpoolFile*mpf = pdb->get_mpf();
                ret = mpf->set_flags(DB_MPOOL_NOFILE, 1);
                if (ret != 0)
                    throw runtime_error(strprintf("CDB() : failed to configure for no temp file backing for database %s", pszFile));
            }

            ret = pdb->open(NULL,      // Txn pointer
                            fMockDb ? NULL : pszFile,   // Filename
                            fMockDb ? pszFile : "main", // Logical db name
                            DB_BTREE,  // Database type
                            nFlags,    // Flags
                            0);

            if (ret != 0)
            {
                delete pdb;
                pdb = NULL;
                --bitdb.mapFileUseCount[strFile];
                strFile = "";
                throw runtime_error(strprintf("CDB() : can't open database file %s, error %d", pszFile, ret));
            }

            if (fCreate && !Exists(string("version")))
            {
                bool fTmp = fReadOnly;
                fReadOnly = false;
                WriteVersion(CLIENT_VERSION);
                fReadOnly = fTmp;
            }

            bitdb.mapDb[strFile] = pdb;
        }
    }
}

static bool IsChainFile(std::string strFile)
{
    if (strFile == "coins.dat" || strFile == "chain.dat")
        return true;

    return false;
}

void CDB::Flush()
{
    if (activeTxn)
        return;

    // Flush database activity from memory pool to disk log
    unsigned int nMinutes = 0;
    if (fReadOnly)
        nMinutes = 1;
    if (IsChainFile(strFile))
        nMinutes = 2;
    if (IsChainFile(strFile) && IsInitialBlockDownload())
        nMinutes = 5;

    bitdb.dbenv.txn_checkpoint(nMinutes ? GetArg("-dblogsize", 100)*1024 : 0, nMinutes, 0);
}

void CDB::Close()
{
    if (!pdb)
        return;
    if (activeTxn)
        activeTxn->abort();
    activeTxn = NULL;
    pdb = NULL;

    Flush();

    {
        LOCK(bitdb.cs_db);
        --bitdb.mapFileUseCount[strFile];
    }
}

void CDBEnv::CloseDb(const string& strFile)
{
    {
        LOCK(cs_db);
        if (mapDb[strFile] != NULL)
        {
            // Close the database handle
            Db* pdb = mapDb[strFile];
            pdb->close(0);
            delete pdb;
            mapDb[strFile] = NULL;
        }
    }
}

bool CDBEnv::RemoveDb(const string& strFile)
{
    this->CloseDb(strFile);

    LOCK(cs_db);
    int rc = dbenv.dbremove(NULL, strFile.c_str(), NULL, DB_AUTO_COMMIT);
    return (rc == 0);
}

bool CDB::Rewrite(const string& strFile, const char* pszSkip)
{
    while (!fShutdown)
    {
        {
            LOCK(bitdb.cs_db);
            if (!bitdb.mapFileUseCount.count(strFile) || bitdb.mapFileUseCount[strFile] == 0)
            {
                // Flush log data to the dat file
                bitdb.CloseDb(strFile);
                bitdb.CheckpointLSN(strFile);
                bitdb.mapFileUseCount.erase(strFile);

                bool fSuccess = true;
                printf("Rewriting %s...\n", strFile.c_str());
                string strFileRes = strFile + ".rewrite";
                { // surround usage of db with extra {}
                    CDB db(strFile.c_str(), "r");
                    Db* pdbCopy = new Db(&bitdb.dbenv, 0);

                    int ret = pdbCopy->open(NULL,                 // Txn pointer
                                            strFileRes.c_str(),   // Filename
                                            "main",    // Logical db name
                                            DB_BTREE,  // Database type
                                            DB_CREATE,    // Flags
                                            0);
                    if (ret > 0)
                    {
                        printf("Cannot create database file %s\n", strFileRes.c_str());
                        fSuccess = false;
                    }

                    Dbc* pcursor = db.GetCursor();
                    if (pcursor)
                        while (fSuccess)
                        {
                            CDataStream ssKey(SER_DISK, CLIENT_VERSION);
                            CDataStream ssValue(SER_DISK, CLIENT_VERSION);
                            int ret = db.ReadAtCursor(pcursor, ssKey, ssValue, DB_NEXT);
                            if (ret == DB_NOTFOUND)
                            {
                                pcursor->close();
                                break;
                            }
                            else if (ret != 0)
                            {
                                pcursor->close();
                                fSuccess = false;
                                break;
                            }
                            if (pszSkip &&
                                strncmp(&ssKey[0], pszSkip, std::min(ssKey.size(), strlen(pszSkip))) == 0)
                                continue;
                            if (strncmp(&ssKey[0], "\x07version", 8) == 0)
                            {
                                // Update version:
                                ssValue.clear();
                                ssValue << CLIENT_VERSION;
                            }
                            Dbt datKey(&ssKey[0], ssKey.size());
                            Dbt datValue(&ssValue[0], ssValue.size());
                            int ret2 = pdbCopy->put(NULL, &datKey, &datValue, DB_NOOVERWRITE);
                            if (ret2 > 0)
                                fSuccess = false;
                        }
                    if (fSuccess)
                    {
                        db.Close();
                        bitdb.CloseDb(strFile);
                        if (pdbCopy->close(0))
                            fSuccess = false;
                        delete pdbCopy;
                    }
                }
                if (fSuccess)
                {
                    Db dbA(&bitdb.dbenv, 0);
                    if (dbA.remove(strFile.c_str(), NULL, 0))
                        fSuccess = false;
                    Db dbB(&bitdb.dbenv, 0);
                    if (dbB.rename(strFileRes.c_str(), NULL, strFile.c_str(), 0))
                        fSuccess = false;
                }
                if (!fSuccess)
                    printf("Rewriting of %s FAILED!\n", strFileRes.c_str());
                return fSuccess;
            }
        }
        Sleep(100);
    }
    return false;
}


void CDBEnv::Flush(bool fShutdown)
{
    int64 nStart = GetTimeMillis();
    // Flush log data to the actual data file
    //  on all files that are not in use
    printf("Flush(%s)%s\n", fShutdown ? "true" : "false", fDbEnvInit ? "" : " db not started");
    if (!fDbEnvInit)
        return;
    {
        LOCK(cs_db);
        map<string, int>::iterator mi = mapFileUseCount.begin();
        while (mi != mapFileUseCount.end())
        {
            string strFile = (*mi).first;
            int nRefCount = (*mi).second;
            printf("%s refcount=%d\n", strFile.c_str(), nRefCount);
            if (nRefCount == 0)
            {
                // Move log data to the dat file
                CloseDb(strFile);
                printf("%s checkpoint\n", strFile.c_str());
                dbenv.txn_checkpoint(0, 0, 0);
                if (!IsChainFile(strFile) || fDetachDB) {
                    printf("%s detach\n", strFile.c_str());
                    if (!fMockDb)
                        dbenv.lsn_reset(strFile.c_str(), 0);
                }
                printf("%s closed\n", strFile.c_str());
                mapFileUseCount.erase(mi++);
            }
            else
                mi++;
        }
        printf("DBFlush(%s)%s ended %15"PRI64d"ms\n", fShutdown ? "true" : "false", fDbEnvInit ? "" : " db not started", GetTimeMillis() - nStart);
        if (fShutdown)
        {
            char** listp;
            if (mapFileUseCount.empty())
            {
                dbenv.log_archive(&listp, DB_ARCH_REMOVE);
                Close();
            }
        }
    }
}






//
// CChainDB and CCoinsDB
//

bool CCoinsDB::HaveCoins(uint256 hash) {
    assert(!fClient);
    return Exists(make_pair('c', hash));
}

bool CCoinsDB::ReadCoins(uint256 hash, CCoins &coins) {
    assert(!fClient);
    return Read(make_pair('c', hash), coins);
}

bool CCoinsDB::WriteCoins(uint256 hash, const CCoins &coins) {
    assert(!fClient);
    if (coins.IsPruned())
        return Erase(make_pair('c', hash));
    else
        return Write(make_pair('c', hash), coins);
}

bool CChainDB::WriteBlockIndex(const CDiskBlockIndex& blockindex)
{
    return Write(make_pair('b', blockindex.GetBlockHash()), blockindex);
}

bool CCoinsDB::ReadHashBestChain(uint256& hashBestChain)
{
    return Read('B', hashBestChain);
}

bool CCoinsDB::WriteHashBestChain(uint256 hashBestChain)
{
    return Write('B', hashBestChain);
}

bool CChainDB::ReadBestInvalidWork(CBigNum& bnBestInvalidWork)
{
    return Read('I', bnBestInvalidWork);
}

bool CChainDB::WriteBestInvalidWork(CBigNum bnBestInvalidWork)
{
    return Write('I', bnBestInvalidWork);
}

bool CChainDB::WriteBlockFileInfo(int nFile, const CBlockFileInfo &info) {
    return Write(make_pair('f', nFile), info);
}

bool CChainDB::ReadBlockFileInfo(int nFile, CBlockFileInfo &info) {
    return Read(make_pair('f', nFile), info);
}

bool CChainDB::WriteLastBlockFile(int nFile) {
    return Write('l', nFile);
}

bool CChainDB::ReadLastBlockFile(int &nFile) {
    return Read('l', nFile);
}

CCoinsViewDB::CCoinsViewDB() : db("cr+") {}
bool CCoinsViewDB::GetCoins(uint256 txid, CCoins &coins) { return db.ReadCoins(txid, coins); }
bool CCoinsViewDB::SetCoins(uint256 txid, const CCoins &coins) { return db.WriteCoins(txid, coins); }
bool CCoinsViewDB::HaveCoins(uint256 txid) { return db.HaveCoins(txid); }
CBlockIndex *CCoinsViewDB::GetBestBlock() {
    uint256 hashBestChain;
    if (!db.ReadHashBestChain(hashBestChain))
        return NULL;
    std::map<uint256, CBlockIndex*>::iterator it = mapBlockIndex.find(hashBestChain);
    if (it == mapBlockIndex.end())
        return NULL;
    return it->second;
}
bool CCoinsViewDB::SetBestBlock(CBlockIndex *pindex) { return db.WriteHashBestChain(pindex->GetBlockHash()); }
bool CCoinsViewDB::BatchWrite(const std::map<uint256, CCoins> &mapCoins, CBlockIndex *pindex) {
    printf("Committing %u changed transactions to coin database...\n", (unsigned int)mapCoins.size());

    if (!db.TxnBegin())
        return false;
    bool fOk = true;
    for (std::map<uint256, CCoins>::const_iterator it = mapCoins.begin(); it != mapCoins.end(); it++) {
        fOk = db.WriteCoins(it->first, it->second);
        if (!fOk)
            break;
    }
    if (fOk)
        fOk = db.WriteHashBestChain(pindex->GetBlockHash());

    if (!fOk)
        db.TxnAbort();
    else
        fOk = db.TxnCommit();

    return fOk;
}

CBlockIndex static * InsertBlockIndex(uint256 hash)
{
    if (hash == 0)
        return NULL;

    // Return existing
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hash);
    if (mi != mapBlockIndex.end())
        return (*mi).second;

    // Create new
    CBlockIndex* pindexNew = new CBlockIndex();
    if (!pindexNew)
        throw runtime_error("LoadBlockIndex() : new CBlockIndex failed");
    mi = mapBlockIndex.insert(make_pair(hash, pindexNew)).first;
    pindexNew->phashBlock = &((*mi).first);

    return pindexNew;
}

bool LoadBlockIndex(CChainDB &chaindb)
{
    if (!chaindb.LoadBlockIndexGuts())
        return false;

    if (fRequestShutdown)
        return true;

    // Calculate bnChainWork
    vector<pair<int, CBlockIndex*> > vSortedByHeight;
    vSortedByHeight.reserve(mapBlockIndex.size());
    BOOST_FOREACH(const PAIRTYPE(uint256, CBlockIndex*)& item, mapBlockIndex)
    {
        CBlockIndex* pindex = item.second;
        vSortedByHeight.push_back(make_pair(pindex->nHeight, pindex));
    }
    sort(vSortedByHeight.begin(), vSortedByHeight.end());
    BOOST_FOREACH(const PAIRTYPE(int, CBlockIndex*)& item, vSortedByHeight)
    {
        CBlockIndex* pindex = item.second;
        pindex->bnChainWork = (pindex->pprev ? pindex->pprev->bnChainWork : 0) + pindex->GetBlockWork();
    }

    // Load block file info
    chaindb.ReadLastBlockFile(nLastBlockFile);
    printf("LoadBlockIndex(): last block file = %i\n", nLastBlockFile);
    if (chaindb.ReadBlockFileInfo(nLastBlockFile, infoLastBlockFile))
        printf("LoadBlockIndex(): last block file: %s\n", infoLastBlockFile.ToString().c_str());
 
    // Load hashBestChain pointer to end of best chain
    pindexBest = pcoinsTip->GetBestBlock();
    if (pindexBest == NULL)
    {
        if (pindexGenesisBlock == NULL)
            return true;
    }
    hashBestChain = pindexBest->GetBlockHash();
    nBestHeight = pindexBest->nHeight;
    bnBestChainWork = pindexBest->bnChainWork;

    // set 'next' pointers in best chain
    CBlockIndex *pindex = pindexBest;
    while(pindex != NULL && pindex->pprev != NULL) {
         CBlockIndex *pindexPrev = pindex->pprev;
         pindexPrev->pnext = pindex;
         pindex = pindexPrev;
    }
    printf("LoadBlockIndex(): hashBestChain=%s  height=%d date=%s\n",
        hashBestChain.ToString().substr(0,20).c_str(), nBestHeight,
        DateTimeStrFormat("%x %H:%M:%S", pindexBest->GetBlockTime()).c_str());

    // Load bnBestInvalidWork, OK if it doesn't exist
    chaindb.ReadBestInvalidWork(bnBestInvalidWork);

    // Verify blocks in the best chain
    int nCheckLevel = GetArg("-checklevel", 1);
    int nCheckDepth = GetArg( "-checkblocks", 2500);
    if (nCheckDepth == 0)
        nCheckDepth = 1000000000; // suffices until the year 19000
    if (nCheckDepth > nBestHeight)
        nCheckDepth = nBestHeight;
    printf("Verifying last %i blocks at level %i\n", nCheckDepth, nCheckLevel);
    CBlockIndex* pindexFork = NULL;
    for (CBlockIndex* pindex = pindexBest; pindex && pindex->pprev; pindex = pindex->pprev)
    {
        if (fRequestShutdown || pindex->nHeight < nBestHeight-nCheckDepth)
            break;
        CBlock block;
        if (!block.ReadFromDisk(pindex))
            return error("LoadBlockIndex() : block.ReadFromDisk failed");
        // check level 1: verify block validity
        if (nCheckLevel>0 && !block.CheckBlock())
        {
            printf("LoadBlockIndex() : *** found bad block at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString().c_str());
            pindexFork = pindex->pprev;
        }
        // TODO: stronger verifications
    }
    if (pindexFork && !fRequestShutdown)
    {
        // TODO: reorg back
        return error("LoadBlockIndex(): chain database corrupted");
    }

    return true;
}



bool CChainDB::LoadBlockIndexGuts()
{
    // Get database cursor
    Dbc* pcursor = GetCursor();
    if (!pcursor)
        return false;

    // Load mapBlockIndex
    unsigned int fFlags = DB_SET_RANGE;
    loop
    {
        // Read next record
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        if (fFlags == DB_SET_RANGE)
            ssKey << make_pair('b', uint256(0));
        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
        int ret = ReadAtCursor(pcursor, ssKey, ssValue, fFlags);
        fFlags = DB_NEXT;
        if (ret == DB_NOTFOUND)
            break;
        else if (ret != 0)
            return false;

        // Unserialize

        try {
        char chType;
        ssKey >> chType;
        if (chType == 'b' && !fRequestShutdown)
        {
            CDiskBlockIndex diskindex;
            ssValue >> diskindex;

            // Construct block index object
            CBlockIndex* pindexNew = InsertBlockIndex(diskindex.GetBlockHash());
            pindexNew->pprev          = InsertBlockIndex(diskindex.hashPrev);
            pindexNew->nHeight        = diskindex.nHeight;
            pindexNew->pos            = diskindex.pos;
            pindexNew->nUndoPos       = diskindex.nUndoPos;
            pindexNew->nVersion       = diskindex.nVersion;
            pindexNew->hashMerkleRoot = diskindex.hashMerkleRoot;
            pindexNew->nTime          = diskindex.nTime;
            pindexNew->nBits          = diskindex.nBits;
            pindexNew->nNonce         = diskindex.nNonce;

            // Watch for genesis block
            if (pindexGenesisBlock == NULL && diskindex.GetBlockHash() == hashGenesisBlock)
                pindexGenesisBlock = pindexNew;

            if (!pindexNew->CheckIndex())
                return error("LoadBlockIndex() : CheckIndex failed at %d", pindexNew->nHeight);
        }
        else
        {
            break; // if shutdown requested or finished loading block index
        }
        }    // try
        catch (std::exception &e) {
            return error("%s() : deserialize error", __PRETTY_FUNCTION__);
        }
    }
    pcursor->close();

    return true;
}





//
// CAddrDB
//


CAddrDB::CAddrDB()
{
    pathAddr = GetDataDir() / "peers.dat";
}

bool CAddrDB::Write(const CAddrMan& addr)
{
    // Generate random temporary filename
    unsigned short randv = 0;
    RAND_bytes((unsigned char *)&randv, sizeof(randv));
    std::string tmpfn = strprintf("peers.dat.%04x", randv);

    // serialize addresses, checksum data up to that point, then append csum
    CDataStream ssPeers(SER_DISK, CLIENT_VERSION);
    ssPeers << FLATDATA(pchMessageStart);
    ssPeers << addr;
    uint256 hash = Hash(ssPeers.begin(), ssPeers.end());
    ssPeers << hash;

    // open temp output file, and associate with CAutoFile
    boost::filesystem::path pathTmp = GetDataDir() / tmpfn;
    FILE *file = fopen(pathTmp.string().c_str(), "wb");
    CAutoFile fileout = CAutoFile(file, SER_DISK, CLIENT_VERSION);
    if (!fileout)
        return error("CAddrman::Write() : open failed");

    // Write and commit header, data
    try {
        fileout << ssPeers;
    }
    catch (std::exception &e) {
        return error("CAddrman::Write() : I/O error");
    }
    FileCommit(fileout);
    fileout.fclose();

    // replace existing peers.dat, if any, with new peers.dat.XXXX
    if (!RenameOver(pathTmp, pathAddr))
        return error("CAddrman::Write() : Rename-into-place failed");

    return true;
}

bool CAddrDB::Read(CAddrMan& addr)
{
    // open input file, and associate with CAutoFile
    FILE *file = fopen(pathAddr.string().c_str(), "rb");
    CAutoFile filein = CAutoFile(file, SER_DISK, CLIENT_VERSION);
    if (!filein)
        return error("CAddrman::Read() : open failed");

    // use file size to size memory buffer
    int fileSize = GetFilesize(filein);
    int dataSize = fileSize - sizeof(uint256);
    vector<unsigned char> vchData;
    vchData.resize(dataSize);
    uint256 hashIn;

    // read data and checksum from file
    try {
        filein.read((char *)&vchData[0], dataSize);
        filein >> hashIn;
    }
    catch (std::exception &e) {
        return error("CAddrman::Read() 2 : I/O error or stream data corrupted");
    }
    filein.fclose();

    CDataStream ssPeers(vchData, SER_DISK, CLIENT_VERSION);

    // verify stored checksum matches input data
    uint256 hashTmp = Hash(ssPeers.begin(), ssPeers.end());
    if (hashIn != hashTmp)
        return error("CAddrman::Read() : checksum mismatch; data corrupted");

    // de-serialize address data
    unsigned char pchMsgTmp[4];
    try {
        ssPeers >> FLATDATA(pchMsgTmp);
        ssPeers >> addr;
    }
    catch (std::exception &e) {
        return error("CAddrman::Read() : I/O error or stream data corrupted");
    }

    // finally, verify the network matches ours
    if (memcmp(pchMsgTmp, pchMessageStart, sizeof(pchMsgTmp)))
        return error("CAddrman::Read() : invalid network magic number");

    return true;
}