C++ Db::get方法代码示例

int main(int argc, char *argv[])
{
	try {
		Db *db = new Db(NULL, 0);
		db->open(NULL, "my.db", NULL, DB_BTREE, DB_CREATE, 0644);

		// populate our massive database.
		// all our strings include null for convenience.
		// Note we have to cast for idiomatic
		// usage, since newer gcc requires it.
		Dbt *keydbt = new Dbt((char *)"key", 4);
		Dbt *datadbt = new Dbt((char *)"data", 5);
		db->put(NULL, keydbt, datadbt, 0);

		// Now, retrieve.  We could use keydbt over again,
		// but that wouldn't be typical in an application.
		Dbt *goodkeydbt = new Dbt((char *)"key", 4);
		Dbt *badkeydbt = new Dbt((char *)"badkey", 7);
		Dbt *resultdbt = new Dbt();
		resultdbt->set_flags(DB_DBT_MALLOC);

		int ret;

		if ((ret = db->get(NULL, goodkeydbt, resultdbt, 0)) != 0) {
			cout << "get: " << DbEnv::strerror(ret) << "\n";
		}
		else {
			char *result = (char *)resultdbt->get_data();
			cout << "got data: " << result << "\n";
		}

		if ((ret = db->get(NULL, badkeydbt, resultdbt, 0)) != 0) {
			// We expect this...
			cout << "get using bad key: "
			     << DbEnv::strerror(ret) << "\n";
		}
		else {
			char *result = (char *)resultdbt->get_data();
			cout << "*** got data using bad key!!: "
			     << result << "\n";
		}
		cout << "finished test\n";
	}
	catch (DbException &dbe) {
		cerr << "Db Exception: " << dbe.what();
	}
	return 0;
}

HeaderGroup* BulkHeaderGroup::getGroup(NewsGroup* ng, QString& articleIndex)
{
    HeaderGroup *hg = 0;

    int ret;
    Dbt groupkey;
    Dbt groupdata;
    memset(&groupkey, 0, sizeof(groupkey));
    memset(&groupdata, 0, sizeof(groupdata));
    groupdata.set_flags(DB_DBT_MALLOC);

    QByteArray ba = articleIndex.toLocal8Bit();
    const char *k= ba.constData();
    groupkey.set_data((void*)k);
    groupkey.set_size(articleIndex.length());

    Db* groupsDb = ng->getGroupingDb();
    ret=groupsDb->get(NULL, &groupkey, &groupdata, 0);
    if (ret != 0) //key not found
    {
        qDebug() << "Failed to find group with key " << articleIndex;
    }
    else
    {
        qDebug() << "Found group with key " << articleIndex;

        hg=new HeaderGroup(articleIndex.length(), (char*)k, (char*)groupdata.get_data());
        void* ptr = groupdata.get_data();
        Q_FREE(ptr);
    }

    return hg;
}

int DiskBDB::Get (const Vdt& dzname, const Vdt& Key, Vdt *Value,stats *stats_update)
{
    Db *DbHandle;
    Dbt dbt_value;
    int ret=0;
    //ret=m_dzManager->GetHandleForPartition("B0",2,DbHandle);
    ret=m_dzManager->Get(dzname,Key,DbHandle);
    if(ret!=0)
    {
        cout<<"Datazone handle not retrieved from datazone manager"<<endl;
        return ret;
    }

    Dbt key(Key.get_data(),Key.get_size());
    dbt_value.set_data((*Value).get_data());
    dbt_value.set_size((*Value).get_size());
    dbt_value.set_ulen((*Value).get_size() );
    dbt_value.set_flags( DB_DBT_USERMEM );

    bool keepTrying=true;
    int numTries=0;
    while(keepTrying && numTries < m_maxDeadlockRetries)
    {
        numTries++;
        try {
            ret=DbHandle->get(NULL,&key,&dbt_value,0);
            keepTrying=false;
            if( ret == 0 )
                Value->set_size( dbt_value.get_size() );
        }
        catch(DbException &e) {
            if(numTries==1)
                printf("DiskBDB Get::%s\n",e.what());

            ret=e.get_errno();

            if(ret==DB_LOCK_DEADLOCK)
            {
                if(stats_update)
                    stats_update->NumDeadlocks++;
            }
            else
                keepTrying=false;

            if( ret==DB_BUFFER_SMALL )
                (*Value).set_size(dbt_value.get_size());
        } catch(exception &e) {
            cout << e.what() << endl;
            return (-1);
        }
    }
    return ret;
}

 string read(const char* skey){
   Dbt key((void*)skey, ::strlen(skey));
   //fetch
   char* buf = _allocHeap(); //keep as heap mem
   Dbt data;
   data.set_data(buf);
   data.set_ulen(MAX_LEN);
   data.set_flags(DB_DBT_USERMEM);
   if( _db->get(nullptr, &key, &data, 0) == DB_NOTFOUND){
     return string("F");
   };
   string res(buf);
   delete[] buf;
   return res;
 };

int main(int argc, const char* argv[]) {

  if (argc !=3) {
      cout << "usage: "<< argv[0] << " <filename> <db filename>" << endl;
      return 1;
  }

  const char* kDatabaseName = argv[2];
  const char* filename = argv[1];

  DbEnv env(0);
  Db* pdb;

  string line;

  bool datamode = false;

  try {

    env.set_error_stream(&cerr);
    env.open("./", DB_CREATE | DB_INIT_MPOOL, 0);

    pdb = new Db(&env, 0);
    // If you want to support duplicated records and make duplicated
    // records sorted by data, you need to call:
    //   pdb->set_flags(DB_DUPSORT);
    // Note that only Btree-typed database supports sorted duplicated
    // records

    // If the database does not exist, create it.  If it exists, clear
    // its content after openning.
    pdb->set_flags( DB_DUP );// | DB_DUPSORT);
    pdb->open(NULL, kDatabaseName, NULL, DB_BTREE, DB_CREATE | DB_TRUNCATE, 0);


    ifstream myfile (filename);
    if (myfile.is_open()) {
        int count = 0;
        while ( myfile.good() ) {
            //if (count++ > 10) {
            //    break;
            //} 
            getline (myfile,line);
            if (!datamode) {
                if ("[DATA]" == line ) {
                    datamode = true;
                }
                continue;
            }
            //cout << (int)line[8]  << endl;
            int index = 0;
            while (32 != (char)line[index]) {
                index++;
            }
            string cjkey = line.substr(0, index);
            while (32 == line[index]) {
                index++;
            }
            string cjdata = line.substr(index, (line.size()-index));
            cout << cjkey << "---" << cjdata << endl;
            Dbt key(const_cast<char*>(cjkey.data()), cjkey.size());
            Dbt value(const_cast<char*>(cjdata.data()), cjdata.size());
            pdb->put(NULL, &key, &value, 0);
        }
        myfile.close();
    } else { 
        cout << "Unable to open file";  
    }


    // You need to set ulen and flags=DB_DBT_USERMEM to prevent Dbt
    // from allocate its own memory but use the memory provided by you.
    string search("aa");
    Dbt key(const_cast<char*>(search.c_str()), search.size());
    char buffer[1024];
    Dbt data;
    data.set_data(buffer);
    data.set_ulen(1024);
    data.set_flags(DB_DBT_USERMEM);
    if (pdb->get(NULL, &key, &data, 0) == DB_NOTFOUND) {
      cerr << "Not found" << endl;
    } else {
      cout << "Found: " << "PPPPPP" <<buffer << "PPPPPP" << endl;
    }

    if (pdb != NULL) {
      pdb->close(0);
      delete pdb;
      // You have to close and delete an exisiting handle, then create
      // a new one before you can use it to remove a database (file).
      pdb = new Db(NULL, 0);
      //pdb->remove("access.db", NULL, 0);
      delete pdb;
    }
    env.close(0);

  } catch (DbException& e) {
    cerr << "DbException: " << e.what() << endl;
    return -1;
  } catch (std::exception& e) {
//.........这里部分代码省略.........