db.h

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 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_WALLET_DB_H
#define BITCOIN_WALLET_DB_H

#include "clientversion.h"
#include "fs.h"
#include "serialize.h"
#include "streams.h"
#include "sync.h"
#include "version.h"

#include <atomic>
#include <map>
#include <string>
#include <vector>

#include <db_cxx.h>

static const unsigned int DEFAULT_WALLET_DBLOGSIZE = 100;
static const bool DEFAULT_WALLET_PRIVDB = true;

class CDBEnv
{
private:
    bool fDbEnvInit;
    bool fMockDb;
    // Don't change into fs::path, as that can result in
    // shutdown problems/crashes caused by a static initialized internal pointer.
    std::string strPath;

    void EnvShutdown();

public:
    mutable CCriticalSection cs_db;
    DbEnv *dbenv;
    std::map<std::string, int> mapFileUseCount;
    std::map<std::string, Db*> mapDb;

    CDBEnv();
    ~CDBEnv();
    void Reset();

    void MakeMock();
    bool IsMock() const { return fMockDb; }

    /**
     * Verify that database file strFile is OK. If it is not,
     * call the callback to try to recover.
     * This must be called BEFORE strFile is opened.
     * Returns true if strFile is OK.
     */
    enum VerifyResult { VERIFY_OK,
                        RECOVER_OK,
                        RECOVER_FAIL };
    typedef bool (*recoverFunc_type)(const std::string& strFile, std::string& out_backup_filename);
    VerifyResult Verify(const std::string& strFile, recoverFunc_type recoverFunc, std::string& out_backup_filename);
    /**
     * Salvage data from a file that Verify says is bad.
     * fAggressive sets the DB_AGGRESSIVE flag (see berkeley DB->verify() method documentation).
     * Appends binary key/value pairs to vResult, returns true if successful.
     * NOTE: reads the entire database into memory, so cannot be used
     * for huge databases.
     */
    typedef std::pair<std::vector<unsigned char>, std::vector<unsigned char> > KeyValPair;
    bool Salvage(const std::string& strFile, bool fAggressive, std::vector<KeyValPair>& vResult);

    bool Open(const fs::path& path);
    void Close();
    void Flush(bool fShutdown);
    void CheckpointLSN(const std::string& strFile);

    void CloseDb(const std::string& strFile);

    DbTxn* TxnBegin(int flags = DB_TXN_WRITE_NOSYNC)
    {
        DbTxn* ptxn = nullptr;
        int ret = dbenv->txn_begin(nullptr, &ptxn, flags);
        if (!ptxn || ret != 0)
            return nullptr;
        return ptxn;
    }
};

extern CDBEnv bitdb;

/** An instance of this class represents one database.
 * For BerkeleyDB this is just a (env, strFile) tuple.
 **/
class CWalletDBWrapper
{
    friend class CDB;
public:
    /** Create dummy DB handle */
    CWalletDBWrapper() : nUpdateCounter(0), nLastSeen(0), nLastFlushed(0), nLastWalletUpdate(0), env(nullptr)
    {
    }

    /** Create DB handle to real database */
    CWalletDBWrapper(CDBEnv *env_in, const std::string &strFile_in) :
        nUpdateCounter(0), nLastSeen(0), nLastFlushed(0), nLastWalletUpdate(0), env(env_in), strFile(strFile_in)
    {
    }

    /** Rewrite the entire database on disk, with the exception of key pszSkip if non-zero
     */
    bool Rewrite(const char* pszSkip=nullptr);

    /** Back up the entire database to a file.
     */
    bool Backup(const std::string& strDest);

    /** Get a name for this database, for debugging etc.
     */
    std::string GetName() const { return strFile; }

    /** Make sure all changes are flushed to disk.
     */
    void Flush(bool shutdown);

    void IncrementUpdateCounter();

    std::atomic<unsigned int> nUpdateCounter;
    unsigned int nLastSeen;
    unsigned int nLastFlushed;
    int64_t nLastWalletUpdate;

private:
    /** BerkeleyDB specific */
    CDBEnv *env;
    std::string strFile;

    /** Return whether this database handle is a dummy for testing.
     * Only to be used at a low level, application should ideally not care
     * about this.
     */
    bool IsDummy() { return env == nullptr; }
};


/** RAII class that provides access to a Berkeley database */
class CDB
{
protected:
    Db* pdb;
    std::string strFile;
    DbTxn* activeTxn;
    bool fReadOnly;
    bool fFlushOnClose;
    CDBEnv *env;

public:
    explicit CDB(CWalletDBWrapper& dbw, const char* pszMode = "r+", bool fFlushOnCloseIn=true);
    ~CDB() { Close(); }

    void Flush();
    void Close();
    static bool Recover(const std::string& filename, void *callbackDataIn, bool (*recoverKVcallback)(void* callbackData, CDataStream ssKey, CDataStream ssValue), std::string& out_backup_filename);

    /* flush the wallet passively (TRY_LOCK)
       ideal to be called periodically */
    static bool PeriodicFlush(CWalletDBWrapper& dbw);
    /* verifies the database environment */
    static bool VerifyEnvironment(const std::string& walletFile, const fs::path& dataDir, std::string& errorStr);
    /* verifies the database file */
    static bool VerifyDatabaseFile(const std::string& walletFile, const fs::path& dataDir, std::string& warningStr, std::string& errorStr, CDBEnv::recoverFunc_type recoverFunc);

private:
    CDB(const CDB&);
    void operator=(const CDB&);

public:
    template <typename K, typename T>
    bool Read(const K& key, T& value)
    {
        if (!pdb)
            return false;

        // Key
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;
        Dbt datKey(ssKey.data(), ssKey.size());

        // Read
        Dbt datValue;
        datValue.set_flags(DB_DBT_MALLOC);
        int ret = pdb->get(activeTxn, &datKey, &datValue, 0);
        memory_cleanse(datKey.get_data(), datKey.get_size());
        bool success = false;
        if (datValue.get_data() != nullptr) {
            // Unserialize value
            try {
                CDataStream ssValue((char*)datValue.get_data(), (char*)datValue.get_data() + datValue.get_size(), SER_DISK, CLIENT_VERSION);
                ssValue >> value;
                success = true;
            } catch (const std::exception&) {
                // In this case success remains 'false'
            }

            // Clear and free memory
            memory_cleanse(datValue.get_data(), datValue.get_size());
            free(datValue.get_data());
        }
        return ret == 0 && success;
    }

    template <typename K, typename T>
    bool Write(const K& key, const T& value, bool fOverwrite = true)
    {
        if (!pdb)
            return true;
        if (fReadOnly)
            assert(!"Write called on database in read-only mode");

        // Key
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;
        Dbt datKey(ssKey.data(), ssKey.size());

        // Value
        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
        ssValue.reserve(10000);
        ssValue << value;
        Dbt datValue(ssValue.data(), ssValue.size());

        // Write
        int ret = pdb->put(activeTxn, &datKey, &datValue, (fOverwrite ? 0 : DB_NOOVERWRITE));

        // Clear memory in case it was a private key
        memory_cleanse(datKey.get_data(), datKey.get_size());
        memory_cleanse(datValue.get_data(), datValue.get_size());
        return (ret == 0);
    }

    template <typename K>
    bool Erase(const K& key)
    {
        if (!pdb)
            return false;
        if (fReadOnly)
            assert(!"Erase called on database in read-only mode");

        // Key
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;
        Dbt datKey(ssKey.data(), ssKey.size());

        // Erase
        int ret = pdb->del(activeTxn, &datKey, 0);

        // Clear memory
        memory_cleanse(datKey.get_data(), datKey.get_size());
        return (ret == 0 || ret == DB_NOTFOUND);
    }

    template <typename K>
    bool Exists(const K& key)
    {
        if (!pdb)
            return false;

        // Key
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;
        Dbt datKey(ssKey.data(), ssKey.size());

        // Exists
        int ret = pdb->exists(activeTxn, &datKey, 0);

        // Clear memory
        memory_cleanse(datKey.get_data(), datKey.get_size());
        return (ret == 0);
    }

    Dbc* GetCursor()
    {
        if (!pdb)
            return nullptr;
        Dbc* pcursor = nullptr;
        int ret = pdb->cursor(nullptr, &pcursor, 0);
        if (ret != 0)
            return nullptr;
        return pcursor;
    }

    int ReadAtCursor(Dbc* pcursor, CDataStream& ssKey, CDataStream& ssValue, bool setRange = false)
    {
        // Read at cursor
        Dbt datKey;
        unsigned int fFlags = DB_NEXT;
        if (setRange) {
            datKey.set_data(ssKey.data());
            datKey.set_size(ssKey.size());
            fFlags = DB_SET_RANGE;
        }
        Dbt datValue;
        datKey.set_flags(DB_DBT_MALLOC);
        datValue.set_flags(DB_DBT_MALLOC);
        int ret = pcursor->get(&datKey, &datValue, fFlags);
        if (ret != 0)
            return ret;
        else if (datKey.get_data() == nullptr || datValue.get_data() == nullptr)
            return 99999;

        // Convert to streams
        ssKey.SetType(SER_DISK);
        ssKey.clear();
        ssKey.write((char*)datKey.get_data(), datKey.get_size());
        ssValue.SetType(SER_DISK);
        ssValue.clear();
        ssValue.write((char*)datValue.get_data(), datValue.get_size());

        // Clear and free memory
        memory_cleanse(datKey.get_data(), datKey.get_size());
        memory_cleanse(datValue.get_data(), datValue.get_size());
        free(datKey.get_data());
        free(datValue.get_data());
        return 0;
    }

public:
    bool TxnBegin()
    {
        if (!pdb || activeTxn)
            return false;
        DbTxn* ptxn = bitdb.TxnBegin();
        if (!ptxn)
            return false;
        activeTxn = ptxn;
        return true;
    }

    bool TxnCommit()
    {
        if (!pdb || !activeTxn)
            return false;
        int ret = activeTxn->commit(0);
        activeTxn = nullptr;
        return (ret == 0);
    }

    bool TxnAbort()
    {
        if (!pdb || !activeTxn)
            return false;
        int ret = activeTxn->abort();
        activeTxn = nullptr;
        return (ret == 0);
    }

    bool ReadVersion(int& nVersion)
    {
        nVersion = 0;
        return Read(std::string("version"), nVersion);
    }

    bool WriteVersion(int nVersion)
    {
        return Write(std::string("version"), nVersion);
    }

    bool static Rewrite(CWalletDBWrapper& dbw, const char* pszSkip = nullptr);
};

#endif // BITCOIN_WALLET_DB_H