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leveldbwrapper.h
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// Copyright (c) 2012-2013 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_LEVELDBWRAPPER_H
#define BITCOIN_LEVELDBWRAPPER_H
#include "serialize.h"
#include "util.h"
#include "version.h"
#include <boost/filesystem/path.hpp>
#include <leveldb/db.h>
#include <leveldb/write_batch.h>
class leveldb_error : public std::runtime_error
{
public:
leveldb_error(const std::string &msg) : std::runtime_error(msg) {}
};
void HandleError(const leveldb::Status &status) throw(leveldb_error);
// Batch of changes queued to be written to a CLevelDBWrapper
class CLevelDBBatch
{
friend class CLevelDBWrapper;
private:
leveldb::WriteBatch batch;
public:
template<typename K, typename V> void Write(const K& key, const V& value) {
CDataStream ssKey(SER_DISK, CLIENT_VERSION);
ssKey.reserve(ssKey.GetSerializeSize(key));
ssKey << key;
leveldb::Slice slKey(&ssKey[0], ssKey.size());
CDataStream ssValue(SER_DISK, CLIENT_VERSION);
ssValue.reserve(ssValue.GetSerializeSize(value));
ssValue << value;
leveldb::Slice slValue(&ssValue[0], ssValue.size());
batch.Put(slKey, slValue);
}
template<typename K> void Erase(const K& key) {
CDataStream ssKey(SER_DISK, CLIENT_VERSION);
ssKey.reserve(ssKey.GetSerializeSize(key));
ssKey << key;
leveldb::Slice slKey(&ssKey[0], ssKey.size());
batch.Delete(slKey);
}
};
class CLevelDBWrapper
{
private:
// custom environment this database is using (may be NULL in case of default environment)
leveldb::Env *penv;
// database options used
leveldb::Options options;
// options used when reading from the database
leveldb::ReadOptions readoptions;
// options used when iterating over values of the database
leveldb::ReadOptions iteroptions;
// options used when writing to the database
leveldb::WriteOptions writeoptions;
// options used when sync writing to the database
leveldb::WriteOptions syncoptions;
// the database itself
leveldb::DB *pdb;
public:
CLevelDBWrapper(const boost::filesystem::path &path, size_t nCacheSize, bool fMemory = false, bool fWipe = false);
~CLevelDBWrapper();
template<typename K, typename V> bool Read(const K& key, V& value) throw(leveldb_error) {
CDataStream ssKey(SER_DISK, CLIENT_VERSION);
ssKey.reserve(ssKey.GetSerializeSize(key));
ssKey << key;
leveldb::Slice slKey(&ssKey[0], 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());
HandleError(status);
}
try {
CDataStream ssValue(strValue.data(), strValue.data() + strValue.size(), SER_DISK, CLIENT_VERSION);
ssValue >> value;
} catch(std::exception &e) {
return false;
}
return true;
}
template<typename K, typename V> bool Write(const K& key, const V& value, bool fSync = false) throw(leveldb_error) {
CLevelDBBatch batch;
batch.Write(key, value);
return WriteBatch(batch, fSync);
}
template<typename K> bool Exists(const K& key) throw(leveldb_error) {
CDataStream ssKey(SER_DISK, CLIENT_VERSION);
ssKey.reserve(ssKey.GetSerializeSize(key));
ssKey << key;
leveldb::Slice slKey(&ssKey[0], 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());
HandleError(status);
}
return true;
}
template<typename K> bool Erase(const K& key, bool fSync = false) throw(leveldb_error) {
CLevelDBBatch batch;
batch.Erase(key);
return WriteBatch(batch, fSync);
}
bool WriteBatch(CLevelDBBatch &batch, bool fSync = false) throw(leveldb_error);
// not available for LevelDB; provide for compatibility with BDB
bool Flush() {
return true;
}
bool Sync() throw(leveldb_error) {
CLevelDBBatch batch;
return WriteBatch(batch, true);
}
// not exactly clean encapsulation, but it's easiest for now
leveldb::Iterator *NewIterator() {
return pdb->NewIterator(iteroptions);
}
};
#endif // BITCOIN_LEVELDBWRAPPER_H

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