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/*************************************************************************************************
* Example for serious use cases of the skip database
*
* Copyright 2020 Google LLC
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of the License at
* https://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*************************************************************************************************/
#include "tkrzw_cmd_util.h"
#include "tkrzw_dbm_skip.h"
// Main routine.
int main(int argc, char** argv) {
// All symbols of Tkrzw are under the namespace "tkrzw".
using namespace tkrzw;
// Creates the database manager.
SkipDBM dbm;
// Tuning parameters.
// Using a 4-byte integer for addressing.
// Setting 1 in 3 records to have skip links.
// Setting 8 as the maximum level of the skip list.
// Assuming the input records are in ascending order.
SkipDBM::TuningParameters tuning_params;
tuning_params.offset_width = 4;
tuning_params.step_unit = 3;
tuning_params.max_level = 8;
tuning_params.insert_in_order = true;
// Opens a new database, OPEN_TRUNCATE means to clear the file content.
// The result is returned as a Status object.
Status status = dbm.OpenAdvanced(
"casket.tks", true, File::OPEN_TRUNCATE, tuning_params);
if (status != Status::SUCCESS) {
// Failure of the Open operation is critical so we stop.
Die("Open failed: ", status);
}
// Prepares records in ascending order of the key.
// The in-order mode requires sorted records.
std::map<std::string, std::string> input_records;
input_records["foo"] = "hop";
input_records["bar"] = "step";
input_records["baz"] = "jump";
// Stores records.
for (const auto& input_record : input_records) {
status = dbm.Set(input_record.first, input_record.second);
if (status != Status::SUCCESS) {
// The Set operation shouldn't fail. So we stop if it happens.
Die("Set failed: ", status);
}
}
// Closes the database.
status = dbm.Close();
if (status != Status::SUCCESS) {
// The Close operation shouldn't fail. So we stop if it happens.
Die("Close failed: ", status);
}
// Opens the existing database as a reader mode.
status = dbm.Open("casket.tks", false);
if (status != Status::SUCCESS) {
// Failure of the Open operation is critical so we stop.
Die("Open failed: ", status);
}
// Retrieves records.
// If there was no record, NOT_FOUND_ERROR would be returned.
std::string value;
status = dbm.Get("foo", &value);
if (status == Status::SUCCESS) {
std::cout << value << std::endl;
} else {
std::cerr << "missing: " << status << std::endl;
}
// Traverses records with forward matching with "ba"
std::unique_ptr<DBM::Iterator> iter = dbm.MakeIterator();
status = iter->Jump("ba");
if (status == Status::NOT_FOUND_ERROR) {
// This could happen if there are no records equal to or greater than it.
std::cerr << "missing: " << status << std::endl;
} else if (status != Status::SUCCESS) {
// Other errors are critical so we stop.
Die("Jump failed: ", status);
}
while (true) {
// Retrieves the current record data.
std::string iter_key, iter_value;
status = iter->Get(&iter_key, &iter_value);
if (status == Status::SUCCESS) {
if (!StrBeginsWith(iter_key, "ba")) break;
std::cout << iter_key << ":" << iter_value << std::endl;
} else {
// This happens at the end of iteration.
if (status != Status::NOT_FOUND_ERROR) {
// Error types other than NOT_FOUND_ERROR are critical.
Die("Iterator::Get failed: ", status);
}
break;
}
// Moves the iterator to the next record.
status = iter->Next();
if (status != Status::SUCCESS) {
// This could happen if another thread cleared the database.
if (status != Status::NOT_FOUND_ERROR) {
// Error types other than NOT_FOUND_ERROR are critical.
Die("Iterator::Get failed: ", status);
}
std::cerr << "missing: " << status << std::endl;
break;
}
}
// Closes the database.
// Even if you forgot to close it, the destructor would close it.
// However, checking the status is a good manner.
status = dbm.Close();
if (status != Status::SUCCESS) {
// The Close operation shouldn't fail. So we stop if it happens.
Die("Close failed: ", status);
}
return 0;
}
// END OF FILE
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