flatdb.h

Go to the documentation of this file.

// Copyright (c) 2014-2020 The Dash Core developers
// Copyright (c) 2021-2022 The PIVX Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://www.opensource.org/licenses/mit-license.php.
 
#ifndef PIVX_FLATDB_H
#define PIVX_FLATDB_H
 
#include "chainparams.h"
#include "clientversion.h"
#include "fs.h"
#include "hash.h"
#include "logging.h"
#include "streams.h"
#include "utiltime.h"
#include "util/system.h"
 
template<typename T>
class CFlatDB
{
private:
    fs::path pathDB;
    std::string strFilename;
    std::string strMagicMessage;
 
    enum ReadResult {
        Ok,
        FileError,
        HashReadError,
        IncorrectHash,
        IncorrectMagicMessage,
        IncorrectMagicNumber,
        IncorrectFormat
    };
 
    bool Write(T& objToSave)
    {
        int64_t nStart = GetTimeMillis();
 
        // serialize, checksum data up to that point, then append checksum
        CDataStream ssObj(SER_DISK, CLIENT_VERSION);
        ssObj << strMagicMessage; // specific magic message for this type of object
        ssObj << Params().MessageStart(); // network specific magic number
        ssObj << objToSave;
        const uint256& hash = Hash(ssObj.begin(), ssObj.end());
        ssObj << hash;
 
        // open output file, and associate with CAutoFile
        FILE* file = fopen(pathDB.string().c_str(), "wb");
        CAutoFile fileout(file, SER_DISK, CLIENT_VERSION);
        if (fileout.IsNull())
            return error("%s: Failed to open file %s", __func__, pathDB.string());
 
        // Write and commit header, data
        try {
            fileout << ssObj;
        }
        catch (std::exception &e) {
            return error("%s: Serialize or I/O error - %s", __func__, e.what());
        }
        fileout.fclose();
 
        LogPrintf("Written info to %s  %dms\n", strFilename, GetTimeMillis() - nStart);
        LogPrintf("     %s\n", objToSave.ToString());
        return true;
    }
 
    ReadResult Read(T& objToLoad)
    {
        int64_t nStart = GetTimeMillis();
        // open input file, and associate with CAutoFile
        FILE* file = fopen(pathDB.string().c_str(), "rb");
        CAutoFile filein(file, SER_DISK, CLIENT_VERSION);
        if (filein.IsNull()) {
            error("%s: Failed to open file %s", __func__, pathDB.string());
            return FileError;
        }
 
        // use file size to size memory buffer
        int fileSize = fs::file_size(pathDB);
        int dataSize = fileSize - sizeof(uint256);
        // Don't try to resize to a negative number if file is small
        if (dataSize < 0) dataSize = 0;
        std::vector<unsigned char> vchData;
        vchData.resize(dataSize);
        uint256 hashIn;
 
        // read data and checksum from file
        try {
            filein.read((char *)vchData.data(), dataSize);
            filein >> hashIn;
        } catch (std::exception &e) {
            error("%s: Deserialize or I/O error - %s", __func__, e.what());
            return HashReadError;
        }
        filein.fclose();
 
        CDataStream ssObj(vchData, SER_DISK, CLIENT_VERSION);
 
        // verify stored checksum matches input data
        uint256 hashTmp = Hash(ssObj.begin(), ssObj.end());
        if (hashIn != hashTmp) {
            error("%s: Checksum mismatch, data corrupted", __func__);
            return IncorrectHash;
        }
 
        unsigned char pchMsgTmp[4];
        std::string strMagicMessageTmp;
        try {
            // de-serialize file header (file specific magic message) and ..
            ssObj >> strMagicMessageTmp;
 
            // ... verify the message matches predefined one
            if (strMagicMessage != strMagicMessageTmp) {
                error("%s: Invalid magic message", __func__);
                return IncorrectMagicMessage;
            }
 
            // de-serialize file header (network specific magic number) and ..
            ssObj >> pchMsgTmp;
 
            // ... verify the network matches ours
            if (memcmp(pchMsgTmp, Params().MessageStart(), sizeof(pchMsgTmp))) {
                error("%s: Invalid network magic number", __func__);
                return IncorrectMagicNumber;
            }
 
            // de-serialize data into T object
            ssObj >> objToLoad;
        } catch (std::exception &e) {
            objToLoad.Clear();
            error("%s: Deserialize or I/O error - %s", __func__, e.what());
            return IncorrectFormat;
        }
 
        LogPrintf("Loaded info from %s  %dms\n", strFilename, GetTimeMillis() - nStart);
        LogPrintf("     %s\n", objToLoad.ToString());
        return Ok;
    }
public:
    CFlatDB(const std::string& strFilenameIn,
            const std::string& strMagicMessageIn) :
            pathDB(GetDataDir() / strFilenameIn), strFilename(strFilenameIn),
            strMagicMessage(strMagicMessageIn) {}
 
    fs::path GetDbPath() const { return pathDB; }
 
    bool Load(T& objToLoad)
    {
        LogPrintf("Reading info from %s...\n", strFilename);
        ReadResult readResult = Read(objToLoad);
        if (readResult == FileError) {
            LogPrintf("Missing file %s, will try to recreate\n", strFilename);
        } else if (readResult != Ok) {
            LogPrintf("Error reading %s: ", strFilename);
            if (readResult == IncorrectFormat) {
                LogPrintf("%s: Magic is ok but data has invalid format, will try to recreate\n", __func__);
            } else {
                LogPrintf("%s: File format is unknown or invalid, please fix it manually\n", __func__);
                // program should exit with an error
                return false;
            }
        }
        return true;
    }
 
    bool Dump(T& objToSave)
    {
        int64_t nStart = GetTimeMillis();
        LogPrintf("Writing info to %s...\n", strFilename);
        Write(objToSave);
        LogPrintf("%s dump finished  %dms\n", strFilename, GetTimeMillis() - nStart);
        return true;
    }
};
 
 
#endif // PIVX_FLATDB_H