dbwrapper.h

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// Copyright (c) 2012-2016 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_DBWRAPPER_H
#define BITCOIN_DBWRAPPER_H
 
#include <common/system.h>
#include <logging.h>
#include <serialize.h>
#include <span.h>
#include <streams.h>
#include <util/fs.h>
#include <util/strencodings.h>
 
#include <leveldb/db.h>
#include <leveldb/write_batch.h>
 
#include <optional>
 
static const size_t DBWRAPPER_PREALLOC_KEY_SIZE = 64;
static const size_t DBWRAPPER_PREALLOC_VALUE_SIZE = 1024;
 
struct DBOptions {
    bool force_compact = false;
};
 
struct DBParams {
    fs::path path;
    size_t cache_bytes;
    bool memory_only = false;
    bool wipe_data = false;
    bool obfuscate = false;
    DBOptions options{};
};
 
class dbwrapper_error : public std::runtime_error {
public:
    explicit dbwrapper_error(const std::string &msg)
        : std::runtime_error(msg) {}
};
 
class CDBWrapper;
 
namespace dbwrapper {
using leveldb::DestroyDB;
}
namespace dbwrapper_private {
 
void HandleError(const leveldb::Status &status);
 
const std::vector<uint8_t> &GetObfuscateKey(const CDBWrapper &w);
}; // namespace dbwrapper_private
 
class CDBBatch {
    friend class CDBWrapper;
 
private:
    const CDBWrapper &parent;
    leveldb::WriteBatch batch;
 
    DataStream ssKey{};
    DataStream ssValue{};
 
    size_t size_estimate{0};
 
public:
    explicit CDBBatch(const CDBWrapper &_parent) : parent(_parent){};
 
    void Clear() {
        batch.Clear();
        size_estimate = 0;
    }
 
    template <typename K, typename V> void Write(const K &key, const V &value) {
        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey << key;
        leveldb::Slice slKey((const char *)ssKey.data(), ssKey.size());
 
        ssValue.reserve(DBWRAPPER_PREALLOC_VALUE_SIZE);
        ssValue << value;
        ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
        leveldb::Slice slValue((const char *)ssValue.data(), ssValue.size());
 
        batch.Put(slKey, slValue);
        // LevelDB serializes writes as:
        // - byte: header
        // - varint: key length (1 byte up to 127B, 2 bytes up to 16383B, ...)
        // - byte[]: key
        // - varint: value length
        // - byte[]: value
        // The formula below assumes the key and value are both less than 16k.
        size_estimate += 3 + (slKey.size() > 127) + slKey.size() +
                         (slValue.size() > 127) + slValue.size();
        ssKey.clear();
        ssValue.clear();
    }
 
    template <typename K> void Erase(const K &key) {
        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey << key;
        leveldb::Slice slKey((const char *)ssKey.data(), ssKey.size());
 
        batch.Delete(slKey);
        // LevelDB serializes erases as:
        // - byte: header
        // - varint: key length
        // - byte[]: key
        // The formula below assumes the key is less than 16kB.
        size_estimate += 2 + (slKey.size() > 127) + slKey.size();
        ssKey.clear();
    }
 
    size_t SizeEstimate() const { return size_estimate; }
};
 
class CDBIterator {
private:
    const CDBWrapper &parent;
    leveldb::Iterator *piter;
 
public:
    CDBIterator(const CDBWrapper &_parent, leveldb::Iterator *_piter)
        : parent(_parent), piter(_piter){};
    ~CDBIterator();
 
    bool Valid() const;
 
    void SeekToFirst();
 
    template <typename K> void Seek(const K &key) {
        DataStream ssKey{};
        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey << key;
        leveldb::Slice slKey((const char *)ssKey.data(), ssKey.size());
        piter->Seek(slKey);
    }
 
    void Next();
 
    template <typename K> bool GetKey(K &key) {
        leveldb::Slice slKey = piter->key();
        try {
            DataStream ssKey{MakeByteSpan(slKey)};
            ssKey >> key;
        } catch (const std::exception &) {
            return false;
        }
        return true;
    }
 
    template <typename V> bool GetValue(V &value) {
        leveldb::Slice slValue = piter->value();
        try {
            DataStream ssValue{MakeByteSpan(slValue)};
            ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
            ssValue >> value;
        } catch (const std::exception &) {
            return false;
        }
        return true;
    }
 
    unsigned int GetValueSize() { return piter->value().size(); }
};
 
class CDBWrapper {
    friend const std::vector<uint8_t> &
    dbwrapper_private::GetObfuscateKey(const CDBWrapper &w);
 
private:
    leveldb::Env *penv;
 
    leveldb::Options options;
 
    leveldb::ReadOptions readoptions;
 
    leveldb::ReadOptions iteroptions;
 
    leveldb::WriteOptions writeoptions;
 
    leveldb::WriteOptions syncoptions;
 
    leveldb::DB *pdb;
 
    std::string m_name;
 
    std::vector<uint8_t> obfuscate_key;
 
    static const std::string OBFUSCATE_KEY_KEY;
 
    static const unsigned int OBFUSCATE_KEY_NUM_BYTES;
 
    std::vector<uint8_t> CreateObfuscateKey() const;
 
    const fs::path m_path;
 
    bool m_is_memory;
 
public:
    CDBWrapper(const DBParams &params);
    ~CDBWrapper();
 
    CDBWrapper(const CDBWrapper &) = delete;
    CDBWrapper &operator=(const CDBWrapper &) = delete;
 
    template <typename K, typename V> bool Read(const K &key, V &value) const {
        DataStream ssKey{};
        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey << key;
        leveldb::Slice slKey((const char *)ssKey.data(), ssKey.size());
 
        std::string strValue;
        leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
        if (!status.ok()) {
            if (status.IsNotFound()) return false;
            LogPrintf("LevelDB read failure: %s\n", status.ToString());
            dbwrapper_private::HandleError(status);
        }
        try {
            DataStream ssValue{MakeByteSpan(strValue)};
            ssValue.Xor(obfuscate_key);
            ssValue >> value;
        } catch (const std::exception &) {
            return false;
        }
        return true;
    }
 
    template <typename K, typename V>
    bool Write(const K &key, const V &value, bool fSync = false) {
        CDBBatch batch(*this);
        batch.Write(key, value);
        return WriteBatch(batch, fSync);
    }
 
    std::optional<fs::path> StoragePath() {
        if (m_is_memory) {
            return {};
        }
        return m_path;
    }
 
    template <typename K> bool Exists(const K &key) const {
        DataStream ssKey{};
        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey << key;
        leveldb::Slice slKey((const char *)ssKey.data(), ssKey.size());
 
        std::string strValue;
        leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
        if (!status.ok()) {
            if (status.IsNotFound()) return false;
            LogPrintf("LevelDB read failure: %s\n", status.ToString());
            dbwrapper_private::HandleError(status);
        }
        return true;
    }
 
    template <typename K> bool Erase(const K &key, bool fSync = false) {
        CDBBatch batch(*this);
        batch.Erase(key);
        return WriteBatch(batch, fSync);
    }
 
    bool WriteBatch(CDBBatch &batch, bool fSync = false);
 
    // Get an estimate of LevelDB memory usage (in bytes).
    size_t DynamicMemoryUsage() const;
 
    CDBIterator *NewIterator() {
        return new CDBIterator(*this, pdb->NewIterator(iteroptions));
    }
 
    bool IsEmpty();
 
    template <typename K>
    size_t EstimateSize(const K &key_begin, const K &key_end) const {
        DataStream ssKey1{}, ssKey2{};
        ssKey1.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey2.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey1 << key_begin;
        ssKey2 << key_end;
        leveldb::Slice slKey1((const char *)ssKey1.data(), ssKey1.size());
        leveldb::Slice slKey2((const char *)ssKey2.data(), ssKey2.size());
        uint64_t size = 0;
        leveldb::Range range(slKey1, slKey2);
        pdb->GetApproximateSizes(&range, 1, &size);
        return size;
    }
 
    template <typename K>
    void CompactRange(const K &key_begin, const K &key_end) const {
        DataStream ssKey1{}, ssKey2{};
        ssKey1.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey2.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
        ssKey1 << key_begin;
        ssKey2 << key_end;
        leveldb::Slice slKey1((const char *)ssKey1.data(), ssKey1.size());
        leveldb::Slice slKey2((const char *)ssKey2.data(), ssKey2.size());
        pdb->CompactRange(&slKey1, &slKey2);
    }
};
 
#endif // BITCOIN_DBWRAPPER_H