src/db.h

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 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_DB_H
#define BITCOIN_DB_H

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

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

#include <boost/filesystem/path.hpp>

#include <db_cxx.h>

class CDiskBlockIndex;
class COutPoint;

extern unsigned int nWalletDBUpdated;

void ThreadFlushWalletDB(const std::string& strWalletFile);


class CDBEnv
{
private:
    bool fDbEnvInit;
    bool fMockDb;
    boost::filesystem::path path;

    void EnvShutdown();

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

    CDBEnv();
    ~CDBEnv();
    void MakeMock();
    bool IsMock() { 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 };
    VerifyResult Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile));
    /**
     * 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(std::string strFile, bool fAggressive, std::vector<KeyValPair>& vResult);

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

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

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

extern CDBEnv bitdb;


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

    explicit CDB(const std::string& strFilename, const char* pszMode = "r+", bool fFlushOnCloseIn=true);
    ~CDB() { Close(); }

public:
    void Flush();
    void Close();

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

protected:
    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[0], ssKey.size());

        // Read
        Dbt datValue;
        datValue.set_flags(DB_DBT_MALLOC);
        int ret = pdb->get(activeTxn, &datKey, &datValue, 0);
        memset(datKey.get_data(), 0, datKey.get_size());
        if (datValue.get_data() == NULL)
            return false;

        // Unserialize value
        try {
            CDataStream ssValue((char*)datValue.get_data(), (char*)datValue.get_data() + datValue.get_size(), SER_DISK, CLIENT_VERSION);
            ssValue >> value;
        } catch (const std::exception&) {
            return false;
        }

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

    template <typename K, typename T>
    bool Write(const K& key, const T& value, bool fOverwrite = true)
    {
        if (!pdb)
            return false;
        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[0], ssKey.size());

        // Value
        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
        ssValue.reserve(10000);
        ssValue << value;
        Dbt datValue(&ssValue[0], ssValue.size());

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

        // Clear memory in case it was a private key
        memset(datKey.get_data(), 0, datKey.get_size());
        memset(datValue.get_data(), 0, 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[0], ssKey.size());

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

        // Clear memory
        memset(datKey.get_data(), 0, 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[0], ssKey.size());

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

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

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

    int ReadAtCursor(Dbc* pcursor, CDataStream& ssKey, CDataStream& ssValue, unsigned int fFlags = DB_NEXT)
    {
        // Read at cursor
        Dbt datKey;
        if (fFlags == DB_SET || fFlags == DB_SET_RANGE || fFlags == DB_GET_BOTH || fFlags == DB_GET_BOTH_RANGE) {
            datKey.set_data(&ssKey[0]);
            datKey.set_size(ssKey.size());
        }
        Dbt datValue;
        if (fFlags == DB_GET_BOTH || fFlags == DB_GET_BOTH_RANGE) {
            datValue.set_data(&ssValue[0]);
            datValue.set_size(ssValue.size());
        }
        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() == NULL || datValue.get_data() == NULL)
            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
        memset(datKey.get_data(), 0, datKey.get_size());
        memset(datValue.get_data(), 0, 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 = NULL;
        return (ret == 0);
    }

    bool TxnAbort()
    {
        if (!pdb || !activeTxn)
            return false;
        int ret = activeTxn->abort();
        activeTxn = NULL;
        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(const std::string& strFile, const char* pszSkip = NULL);
};

#endif // BITCOIN_DB_H