bdb.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <wallet/bdb.h>
#include <wallet/db.h>
 
#include <common/args.h>
#include <compat/compat.h>
#include <logging.h>
#include <sync.h>
#include <util/fs.h>
#include <util/fs_helpers.h>
#include <util/strencodings.h>
#include <util/time.h>
#include <util/translation.h>
 
#include <cstdint>
#ifndef WIN32
#include <sys/stat.h>
#endif
 
namespace {
void CheckUniqueFileid(const BerkeleyEnvironment &env,
                       const std::string &filename, Db &db,
                       WalletDatabaseFileId &fileid) {
    if (env.IsMock()) {
        return;
    }
 
    int ret = db.get_mpf()->get_fileid(fileid.value);
    if (ret != 0) {
        throw std::runtime_error(
            strprintf("BerkeleyDatabase: Can't open database %s (get_fileid "
                      "failed with %d)",
                      filename, ret));
    }
 
    for (const auto &item : env.m_fileids) {
        if (fileid == item.second && &fileid != &item.second) {
            throw std::runtime_error(
                strprintf("BerkeleyDatabase: Can't open database %s "
                          "(duplicates fileid %s "
                          "from %s)",
                          filename, HexStr(item.second.value), item.first));
        }
    }
}
 
RecursiveMutex cs_db;
 
std::map<std::string, std::weak_ptr<BerkeleyEnvironment>>
    g_dbenvs GUARDED_BY(cs_db);
} // namespace
 
bool WalletDatabaseFileId::operator==(const WalletDatabaseFileId &rhs) const {
    return memcmp(value, &rhs.value, sizeof(value)) == 0;
}
 
std::shared_ptr<BerkeleyEnvironment>
GetWalletEnv(const fs::path &wallet_path, std::string &database_filename) {
    fs::path env_directory;
    SplitWalletPath(wallet_path, env_directory, database_filename);
    LOCK(cs_db);
    auto inserted = g_dbenvs.emplace(fs::PathToString(env_directory),
                                     std::weak_ptr<BerkeleyEnvironment>());
    if (inserted.second) {
        auto env = std::make_shared<BerkeleyEnvironment>(env_directory);
        inserted.first->second = env;
        return env;
    }
    return inserted.first->second.lock();
}
 
//
// BerkeleyBatch
//
 
void BerkeleyEnvironment::Close() {
    if (!fDbEnvInit) {
        return;
    }
 
    fDbEnvInit = false;
 
    for (auto &db : m_databases) {
        BerkeleyDatabase &database = db.second.get();
        assert(database.m_refcount <= 0);
        if (database.m_db) {
            database.m_db->close(0);
            database.m_db.reset();
        }
    }
 
    FILE *error_file = nullptr;
    dbenv->get_errfile(&error_file);
 
    int ret = dbenv->close(0);
    if (ret != 0) {
        LogPrintf("BerkeleyEnvironment::Close: Error %d closing database "
                  "environment: %s\n",
                  ret, DbEnv::strerror(ret));
    }
    if (!fMockDb) {
        DbEnv(uint32_t(0)).remove(strPath.c_str(), 0);
    }
 
    if (error_file) {
        fclose(error_file);
    }
 
    UnlockDirectory(fs::PathFromString(strPath), ".walletlock");
}
 
void BerkeleyEnvironment::Reset() {
    dbenv.reset(new DbEnv(DB_CXX_NO_EXCEPTIONS));
    fDbEnvInit = false;
    fMockDb = false;
}
 
BerkeleyEnvironment::BerkeleyEnvironment(const fs::path &dir_path)
    : strPath(fs::PathToString(dir_path)) {
    Reset();
}
 
BerkeleyEnvironment::~BerkeleyEnvironment() {
    LOCK(cs_db);
    g_dbenvs.erase(strPath);
    Close();
}
 
bool BerkeleyEnvironment::Open(bilingual_str &err) {
    if (fDbEnvInit) {
        return true;
    }
 
    fs::path pathIn = fs::PathFromString(strPath);
    TryCreateDirectories(pathIn);
    if (util::LockDirectory(pathIn, ".walletlock") !=
        util::LockResult::Success) {
        LogPrintf("Cannot obtain a lock on wallet directory %s. Another "
                  "instance of bitcoin may be using it.\n",
                  strPath);
        err = strprintf(_("Error initializing wallet database environment %s!"),
                        fs::quoted(fs::PathToString(Directory())));
        return false;
    }
 
    fs::path pathLogDir = pathIn / "database";
    TryCreateDirectories(pathLogDir);
    fs::path pathErrorFile = pathIn / "db.log";
    LogPrintf("BerkeleyEnvironment::Open: LogDir=%s ErrorFile=%s\n",
              fs::PathToString(pathLogDir), fs::PathToString(pathErrorFile));
 
    unsigned int nEnvFlags = 0;
    if (gArgs.GetBoolArg("-privdb", DEFAULT_WALLET_PRIVDB)) {
        nEnvFlags |= DB_PRIVATE;
    }
 
    dbenv->set_lg_dir(fs::PathToString(pathLogDir).c_str());
    // 1 MiB should be enough for just the wallet
    dbenv->set_cachesize(0, 0x100000, 1);
    dbenv->set_lg_bsize(0x10000);
    dbenv->set_lg_max(1048576);
    dbenv->set_lk_max_locks(40000);
    dbenv->set_lk_max_objects(40000);
    dbenv->set_errfile(fsbridge::fopen(pathErrorFile, "a"));
    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(strPath.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) {
        LogPrintf("BerkeleyEnvironment::Open: Error %d opening database "
                  "environment: %s\n",
                  ret, DbEnv::strerror(ret));
        int ret2 = dbenv->close(0);
        if (ret2 != 0) {
            LogPrintf("BerkeleyEnvironment::Open: Error %d closing failed "
                      "database environment: %s\n",
                      ret2, DbEnv::strerror(ret2));
        }
        Reset();
        err = strprintf(_("Error initializing wallet database environment %s!"),
                        fs::quoted(fs::PathToString(Directory())));
        if (ret == DB_RUNRECOVERY) {
            err += Untranslated(" ") +
                   _("This error could occur if this wallet was not shutdown "
                     "cleanly and was last loaded using a build with a newer "
                     "version of Berkeley DB. If so, please use the software "
                     "that last loaded this wallet");
        }
        return false;
    }
 
    fDbEnvInit = true;
    fMockDb = false;
    return true;
}
 
BerkeleyEnvironment::BerkeleyEnvironment() {
    Reset();
 
    LogDebug(BCLog::WALLETDB, "BerkeleyEnvironment::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(nullptr,
                    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 std::runtime_error(
            strprintf("BerkeleyEnvironment::MakeMock: Error %d opening "
                      "database environment.",
                      ret));
    }
 
    fDbEnvInit = true;
    fMockDb = true;
}
 
BerkeleyBatch::SafeDbt::SafeDbt() {
    m_dbt.set_flags(DB_DBT_MALLOC);
}
 
BerkeleyBatch::SafeDbt::SafeDbt(void *data, size_t size) : m_dbt(data, size) {}
 
BerkeleyBatch::SafeDbt::~SafeDbt() {
    if (m_dbt.get_data() != nullptr) {
        // Clear memory, e.g. in case it was a private key
        memory_cleanse(m_dbt.get_data(), m_dbt.get_size());
        // under DB_DBT_MALLOC, data is malloced by the Dbt, but must be
        // freed by the caller.
        // https://docs.oracle.com/cd/E17275_01/html/api_reference/C/dbt.html
        if (m_dbt.get_flags() & DB_DBT_MALLOC) {
            free(m_dbt.get_data());
        }
    }
}
 
const void *BerkeleyBatch::SafeDbt::get_data() const {
    return m_dbt.get_data();
}
 
uint32_t BerkeleyBatch::SafeDbt::get_size() const {
    return m_dbt.get_size();
}
 
BerkeleyBatch::SafeDbt::operator Dbt *() {
    return &m_dbt;
}
 
bool BerkeleyDatabase::Verify(bilingual_str &errorStr) {
    fs::path walletDir = env->Directory();
    fs::path file_path = walletDir / strFile;
 
    LogPrintf("Using BerkeleyDB version %s\n", BerkeleyDatabaseVersion());
    LogPrintf("Using wallet %s\n", fs::PathToString(file_path));
 
    if (!env->Open(errorStr)) {
        return false;
    }
 
    if (fs::exists(file_path)) {
        assert(m_refcount == 0);
 
        Db db(env->dbenv.get(), 0);
        int result = db.verify(strFile.c_str(), nullptr, nullptr, 0);
        if (result != 0) {
            errorStr =
                strprintf(_("%s corrupt. Try using the wallet tool "
                            "bitcoin-wallet to salvage or restoring a backup."),
                          fs::quoted(fs::PathToString(file_path)));
            return false;
        }
    }
    // also return true if files does not exists
    return true;
}
 
void BerkeleyEnvironment::CheckpointLSN(const std::string &strFile) {
    dbenv->txn_checkpoint(0, 0, 0);
    if (fMockDb) {
        return;
    }
    dbenv->lsn_reset(strFile.c_str(), 0);
}
 
BerkeleyDatabase::~BerkeleyDatabase() {
    if (env) {
        LOCK(cs_db);
        env->CloseDb(strFile);
        assert(!m_db);
        size_t erased = env->m_databases.erase(strFile);
        assert(erased == 1);
        env->m_fileids.erase(strFile);
    }
}
 
BerkeleyBatch::BerkeleyBatch(BerkeleyDatabase &database, const bool read_only,
                             bool fFlushOnCloseIn)
    : m_database(database) {
    database.AddRef();
    database.Open();
    fReadOnly = read_only;
    fFlushOnClose = fFlushOnCloseIn;
    env = database.env.get();
    pdb = database.m_db.get();
    strFile = database.strFile;
}
 
void BerkeleyDatabase::Open() {
    unsigned int nFlags = DB_THREAD | DB_CREATE;
 
    {
        LOCK(cs_db);
        bilingual_str open_err;
        if (!env->Open(open_err)) {
            throw std::runtime_error(
                "BerkeleyDatabase: Failed to open database environment.");
        }
 
        if (m_db == nullptr) {
            int ret;
            std::unique_ptr<Db> pdb_temp =
                std::make_unique<Db>(env->dbenv.get(), 0);
 
            bool fMockDb = env->IsMock();
            if (fMockDb) {
                DbMpoolFile *mpf = pdb_temp->get_mpf();
                ret = mpf->set_flags(DB_MPOOL_NOFILE, 1);
                if (ret != 0) {
                    throw std::runtime_error(strprintf(
                        "BerkeleyDatabase: Failed to configure for no "
                        "temp file backing for database %s",
                        strFile));
                }
            }
 
            ret = pdb_temp->open(
                nullptr,                             // Txn pointer
                fMockDb ? nullptr : strFile.c_str(), // Filename
                fMockDb ? strFile.c_str() : "main",  // Logical db name
                DB_BTREE,                            // Database type
                nFlags,                              // Flags
                0);
 
            if (ret != 0) {
                throw std::runtime_error(strprintf(
                    "BerkeleyDatabase: Error %d, can't open database %s", ret,
                    strFile));
            }
 
            // Call CheckUniqueFileid on the containing BDB environment to
            // avoid BDB data consistency bugs that happen when different data
            // files in the same environment have the same fileid.
            CheckUniqueFileid(*env, strFile, *pdb_temp,
                              this->env->m_fileids[strFile]);
 
            m_db.reset(pdb_temp.release());
        }
    }
}
 
void BerkeleyBatch::Flush() {
    if (activeTxn) {
        return;
    }
 
    // Flush database activity from memory pool to disk log
    unsigned int nMinutes = 0;
    if (fReadOnly) {
        nMinutes = 1;
    }
 
    // env is nullptr for dummy databases (i.e. in tests). Don't actually flush
    // if env is nullptr so we don't segfault
    if (env) {
        env->dbenv->txn_checkpoint(
            nMinutes
                ? gArgs.GetIntArg("-dblogsize", DEFAULT_WALLET_DBLOGSIZE) * 1024
                : 0,
            nMinutes, 0);
    }
}
 
void BerkeleyDatabase::IncrementUpdateCounter() {
    ++nUpdateCounter;
}
 
BerkeleyBatch::~BerkeleyBatch() {
    Close();
    m_database.RemoveRef();
}
 
void BerkeleyBatch::Close() {
    if (!pdb) {
        return;
    }
    if (activeTxn) {
        activeTxn->abort();
    }
    activeTxn = nullptr;
    pdb = nullptr;
    CloseCursor();
 
    if (fFlushOnClose) {
        Flush();
    }
}
 
void BerkeleyEnvironment::CloseDb(const std::string &strFile) {
    LOCK(cs_db);
    auto it = m_databases.find(strFile);
    assert(it != m_databases.end());
    BerkeleyDatabase &database = it->second.get();
    if (database.m_db) {
        // Close the database handle
        database.m_db->close(0);
        database.m_db.reset();
    }
}
 
void BerkeleyEnvironment::ReloadDbEnv() {
    // Make sure that no Db's are in use
    AssertLockNotHeld(cs_db);
    std::unique_lock<RecursiveMutex> lock(cs_db);
    m_db_in_use.wait(lock, [this]() {
        for (auto &db : m_databases) {
            if (db.second.get().m_refcount > 0) {
                return false;
            }
        }
        return true;
    });
 
    std::vector<std::string> filenames;
    filenames.reserve(m_databases.size());
    for (const auto &it : m_databases) {
        filenames.push_back(it.first);
    }
    // Close the individual Db's
    for (const std::string &filename : filenames) {
        CloseDb(filename);
    }
    // Reset the environment
    // This will flush and close the environment
    Flush(true);
    Reset();
    bilingual_str open_err;
    Open(open_err);
}
 
bool BerkeleyDatabase::Rewrite(const char *pszSkip) {
    while (true) {
        {
            LOCK(cs_db);
            if (m_refcount <= 0) {
                // Flush log data to the dat file
                env->CloseDb(strFile);
                env->CheckpointLSN(strFile);
                m_refcount = -1;
 
                bool fSuccess = true;
                LogPrintf("BerkeleyBatch::Rewrite: Rewriting %s...\n", strFile);
                std::string strFileRes = strFile + ".rewrite";
                { // surround usage of db with extra {}
                    BerkeleyBatch db(*this, true);
                    std::unique_ptr<Db> pdbCopy =
                        std::make_unique<Db>(env->dbenv.get(), 0);
 
                    int ret = pdbCopy->open(nullptr,            // Txn pointer
                                            strFileRes.c_str(), // Filename
                                            "main",    // Logical db name
                                            DB_BTREE,  // Database type
                                            DB_CREATE, // Flags
                                            0);
                    if (ret > 0) {
                        LogPrintf("BerkeleyBatch::Rewrite: Can't create "
                                  "database file %s\n",
                                  strFileRes);
                        fSuccess = false;
                    }
 
                    if (db.StartCursor()) {
                        while (fSuccess) {
                            DataStream ssKey{};
                            DataStream ssValue{};
                            bool complete;
                            bool ret1 =
                                db.ReadAtCursor(ssKey, ssValue, complete);
                            if (complete) {
                                break;
                            }
                            if (!ret1) {
                                fSuccess = false;
                                break;
                            }
                            if (pszSkip &&
                                strncmp((const char *)ssKey.data(), pszSkip,
                                        std::min(ssKey.size(),
                                                 strlen(pszSkip))) == 0) {
                                continue;
                            }
                            if (strncmp((const char *)ssKey.data(),
                                        "\x07version", 8) == 0) {
                                // Update version:
                                ssValue.clear();
                                ssValue << CLIENT_VERSION;
                            }
                            Dbt datKey(ssKey.data(), ssKey.size());
                            Dbt datValue(ssValue.data(), ssValue.size());
                            int ret2 = pdbCopy->put(nullptr, &datKey, &datValue,
                                                    DB_NOOVERWRITE);
                            if (ret2 > 0) {
                                fSuccess = false;
                            }
                        }
                        db.CloseCursor();
                    }
                    if (fSuccess) {
                        db.Close();
                        env->CloseDb(strFile);
                        if (pdbCopy->close(0)) {
                            fSuccess = false;
                        }
                    } else {
                        pdbCopy->close(0);
                    }
                }
                if (fSuccess) {
                    Db dbA(env->dbenv.get(), 0);
                    if (dbA.remove(strFile.c_str(), nullptr, 0)) {
                        fSuccess = false;
                    }
                    Db dbB(env->dbenv.get(), 0);
                    if (dbB.rename(strFileRes.c_str(), nullptr, strFile.c_str(),
                                   0)) {
                        fSuccess = false;
                    }
                }
                if (!fSuccess) {
                    LogPrintf("BerkeleyBatch::Rewrite: Failed to rewrite "
                              "database file %s\n",
                              strFileRes);
                }
                return fSuccess;
            }
        }
        UninterruptibleSleep(std::chrono::milliseconds{100});
    }
}
 
void BerkeleyEnvironment::Flush(bool fShutdown) {
    int64_t nStart = GetTimeMillis();
    // Flush log data to the actual data file on all files that are not in use
    LogDebug(BCLog::WALLETDB, "BerkeleyEnvironment::Flush: [%s] Flush(%s)%s\n",
             strPath, fShutdown ? "true" : "false",
             fDbEnvInit ? "" : " database not started");
    if (!fDbEnvInit) {
        return;
    }
    {
        LOCK(cs_db);
        bool no_dbs_accessed = true;
        for (auto &db_it : m_databases) {
            std::string strFile = db_it.first;
            int nRefCount = db_it.second.get().m_refcount;
            if (nRefCount < 0) {
                continue;
            }
            LogDebug(
                BCLog::WALLETDB,
                "BerkeleyEnvironment::Flush: Flushing %s (refcount = %d)...\n",
                strFile, nRefCount);
            if (nRefCount == 0) {
                // Move log data to the dat file
                CloseDb(strFile);
                LogDebug(BCLog::WALLETDB,
                         "BerkeleyEnvironment::Flush: %s checkpoint\n",
                         strFile);
                dbenv->txn_checkpoint(0, 0, 0);
                LogDebug(BCLog::WALLETDB,
                         "BerkeleyEnvironment::Flush: %s detach\n", strFile);
                if (!fMockDb) {
                    dbenv->lsn_reset(strFile.c_str(), 0);
                }
                LogDebug(BCLog::WALLETDB,
                         "BerkeleyEnvironment::Flush: %s closed\n", strFile);
                nRefCount = -1;
            } else {
                no_dbs_accessed = false;
            }
        }
        LogDebug(BCLog::WALLETDB,
                 "BerkeleyEnvironment::Flush: Flush(%s)%s took %15dms\n",
                 fShutdown ? "true" : "false",
                 fDbEnvInit ? "" : " database not started",
                 GetTimeMillis() - nStart);
        if (fShutdown) {
            char **listp;
            if (no_dbs_accessed) {
                dbenv->log_archive(&listp, DB_ARCH_REMOVE);
                Close();
                if (!fMockDb) {
                    fs::remove_all(fs::PathFromString(strPath) / "database");
                }
            }
        }
    }
}
 
bool BerkeleyDatabase::PeriodicFlush() {
    // Don't flush if we can't acquire the lock.
    TRY_LOCK(cs_db, lockDb);
    if (!lockDb) {
        return false;
    }
 
    // Don't flush if any databases are in use
    for (auto &it : env->m_databases) {
        if (it.second.get().m_refcount > 0) {
            return false;
        }
    }
 
    // Don't flush if there haven't been any batch writes for this database.
    if (m_refcount < 0) {
        return false;
    }
 
    LogDebug(BCLog::WALLETDB, "Flushing %s\n", strFile);
    int64_t nStart = GetTimeMillis();
 
    // Flush wallet file so it's self contained
    env->CloseDb(strFile);
    env->CheckpointLSN(strFile);
    m_refcount = -1;
 
    LogDebug(BCLog::WALLETDB, "Flushed %s %dms\n", strFile,
             GetTimeMillis() - nStart);
 
    return true;
}
 
bool BerkeleyDatabase::Backup(const std::string &strDest) const {
    while (true) {
        {
            LOCK(cs_db);
            if (m_refcount <= 0) {
                // Flush log data to the dat file
                env->CloseDb(strFile);
                env->CheckpointLSN(strFile);
 
                // Copy wallet file.
                fs::path pathSrc = env->Directory() / strFile;
                fs::path pathDest(fs::PathFromString(strDest));
                if (fs::is_directory(pathDest)) {
                    pathDest /= fs::PathFromString(strFile);
                }
 
                try {
                    if (fs::exists(pathDest) &&
                        fs::equivalent(pathSrc, pathDest)) {
                        LogPrintf("cannot backup to wallet source file %s\n",
                                  fs::PathToString(pathDest));
                        return false;
                    }
 
                    fs::copy_file(pathSrc, pathDest,
                                  fs::copy_options::overwrite_existing);
                    LogPrintf("copied %s to %s\n", strFile,
                              fs::PathToString(pathDest));
                    return true;
                } catch (const fs::filesystem_error &e) {
                    LogPrintf("error copying %s to %s - %s\n", strFile,
                              fs::PathToString(pathDest), e.code().message());
                    return false;
                }
            }
        }
        UninterruptibleSleep(std::chrono::milliseconds{100});
    }
}
 
void BerkeleyDatabase::Flush() {
    env->Flush(false);
}
 
void BerkeleyDatabase::Close() {
    env->Flush(true);
}
 
void BerkeleyDatabase::ReloadDbEnv() {
    env->ReloadDbEnv();
}
 
bool BerkeleyBatch::StartCursor() {
    assert(!m_cursor);
    if (!pdb) {
        return false;
    }
    int ret = pdb->cursor(nullptr, &m_cursor, 0);
    return ret == 0;
}
 
bool BerkeleyBatch::ReadAtCursor(DataStream &ssKey, DataStream &ssValue,
                                 bool &complete) {
    complete = false;
    if (m_cursor == nullptr) {
        return false;
    }
    // Read at cursor
    SafeDbt datKey;
    SafeDbt datValue;
    int ret = m_cursor->get(datKey, datValue, DB_NEXT);
    if (ret == DB_NOTFOUND) {
        complete = true;
    }
    if (ret != 0) {
        return false;
    } else if (datKey.get_data() == nullptr || datValue.get_data() == nullptr) {
        return false;
    }
 
    // Convert to streams
    ssKey.clear();
    ssKey.write({BytePtr(datKey.get_data()), datKey.get_size()});
    ssValue.clear();
    ssValue.write({BytePtr(datValue.get_data()), datValue.get_size()});
    return true;
}
 
void BerkeleyBatch::CloseCursor() {
    if (!m_cursor) {
        return;
    }
    m_cursor->close();
    m_cursor = nullptr;
}
 
bool BerkeleyBatch::TxnBegin() {
    if (!pdb || activeTxn) {
        return false;
    }
    DbTxn *ptxn = env->TxnBegin();
    if (!ptxn) {
        return false;
    }
    activeTxn = ptxn;
    return true;
}
 
bool BerkeleyBatch::TxnCommit() {
    if (!pdb || !activeTxn) {
        return false;
    }
    int ret = activeTxn->commit(0);
    activeTxn = nullptr;
    return (ret == 0);
}
 
bool BerkeleyBatch::TxnAbort() {
    if (!pdb || !activeTxn) {
        return false;
    }
    int ret = activeTxn->abort();
    activeTxn = nullptr;
    return (ret == 0);
}
 
std::string BerkeleyDatabaseVersion() {
    return DbEnv::version(nullptr, nullptr, nullptr);
}
 
bool BerkeleyBatch::ReadKey(DataStream &&key, DataStream &value) {
    if (!pdb) {
        return false;
    }
 
    SafeDbt datKey(key.data(), key.size());
 
    SafeDbt datValue;
    int ret = pdb->get(activeTxn, datKey, datValue, 0);
    if (ret == 0 && datValue.get_data() != nullptr) {
        value.write({BytePtr(datValue.get_data()), datValue.get_size()});
        return true;
    }
    return false;
}
 
bool BerkeleyBatch::WriteKey(DataStream &&key, DataStream &&value,
                             bool overwrite) {
    if (!pdb) {
        return false;
    }
 
    if (fReadOnly) {
        assert(!"Write called on database in read-only mode");
    }
 
    SafeDbt datKey(key.data(), key.size());
 
    SafeDbt datValue(value.data(), value.size());
 
    int ret =
        pdb->put(activeTxn, datKey, datValue, (overwrite ? 0 : DB_NOOVERWRITE));
    return (ret == 0);
}
 
bool BerkeleyBatch::EraseKey(DataStream &&key) {
    if (!pdb) {
        return false;
    }
    if (fReadOnly) {
        assert(!"Erase called on database in read-only mode");
    }
 
    SafeDbt datKey(key.data(), key.size());
 
    int ret = pdb->del(activeTxn, datKey, 0);
    return (ret == 0 || ret == DB_NOTFOUND);
}
 
bool BerkeleyBatch::HasKey(DataStream &&key) {
    if (!pdb) {
        return false;
    }
 
    SafeDbt datKey(key.data(), key.size());
 
    int ret = pdb->exists(activeTxn, datKey, 0);
    return ret == 0;
}
 
void BerkeleyDatabase::AddRef() {
    LOCK(cs_db);
    if (m_refcount < 0) {
        m_refcount = 1;
    } else {
        m_refcount++;
    }
}
 
void BerkeleyDatabase::RemoveRef() {
    LOCK(cs_db);
    m_refcount--;
    if (env) {
        env->m_db_in_use.notify_all();
    }
}
 
std::unique_ptr<DatabaseBatch>
BerkeleyDatabase::MakeBatch(bool flush_on_close) {
    return std::make_unique<BerkeleyBatch>(*this, false, flush_on_close);
}
 
bool ExistsBerkeleyDatabase(const fs::path &path) {
    fs::path env_directory;
    std::string data_filename;
    SplitWalletPath(path, env_directory, data_filename);
    return IsBerkeleyBtree(env_directory / data_filename);
}
 
std::unique_ptr<BerkeleyDatabase>
MakeBerkeleyDatabase(const fs::path &path, const DatabaseOptions &options,
                     DatabaseStatus &status, bilingual_str &error) {
    std::unique_ptr<BerkeleyDatabase> db;
    {
        // Lock env.m_databases until insert in BerkeleyDatabase constructor
        LOCK(cs_db);
        std::string data_filename;
        std::shared_ptr<BerkeleyEnvironment> env =
            GetWalletEnv(path, data_filename);
        if (!env) {
            error = Untranslated(
                strprintf("Failed to load database. Data file '%s' is in the "
                          "process of being unloaded. Try again later.",
                          fs::PathToString(env->Directory() / data_filename)));
            status = DatabaseStatus::FAILED_LOAD;
            return nullptr;
        }
        if (env->m_databases.count(data_filename)) {
            error = Untranslated(strprintf(
                "Refusing to load database. Data file '%s' is already loaded.",
                fs::PathToString(env->Directory() / data_filename)));
            status = DatabaseStatus::FAILED_ALREADY_LOADED;
            return nullptr;
        }
        db = std::make_unique<BerkeleyDatabase>(std::move(env),
                                                std::move(data_filename));
    }
 
    if (options.verify && !db->Verify(error)) {
        status = DatabaseStatus::FAILED_VERIFY;
        return nullptr;
    }
 
    status = DatabaseStatus::SUCCESS;
    return db;
}