feat(cpp): add db and env

Former-commit-id: fc2f7219ff7806ca1f98d402ac5120e6174d5e01

cpp/src/db.h

+#ifndef VECENGINE_DB_H_
+#define VECENGINE_DB_H_
+
+#include "options.h"
+
+namespace vecengine {
+
+class Env;
+
+class DB {
+public:
+    static DB* Open(const Options& options_, const std::string& name_);
+
+    DB() = default;
+    DB(const DB&) = delete;
+    DB& operator=(const DB&) = delete;
+
+    virtual ~DB();
+}; // DB
+
+} // namespace vecengine
+
+#endif // VECENGINE_DB_H_

cpp/src/db_impl.cpp

+include "db_impl.h"
+
+namespace vecengine {
+
+DB::DB(const Options& options_, const std::string& name_)
+    : _dbname(name_),
+      _env(options_.env),
+      _options(options_) {
+}
+
+} // namespace vecengine

cpp/src/db_impl.h

+#ifndef VECENGINE_DB_IMPL_H_
+#define VECENGINE_DB_IMPL_H_
+
+#include "db.h"
+
+namespace vecengine {
+
+class Env;
+
+class DBImpl : public DB {
+public:
+    DBImpl(const Options& options_, const std::string& name_);
+
+    virtual ~DBImpl();
+private:
+    const _dbname;
+    Env* const _env;
+    const Options _options;
+
+}; // DBImpl
+
+} // namespace vecengine
+
+#endif // VECENGINE_DB_IMPL_H_

cpp/src/env.cpp

+#inlcude "env.h"
+
+namespace vecengine {
+
+DBConfig::DBConfig()
+    : _mem_sync_interval(10),
+      _file_merge_trigger_number(20),
+      _index_file_build_trigger_size(100000) {
+}
+
+} // namespace vecengine

cpp/src/env.h

+#ifndef STORAGE_VECENGINE_ENV_H_
+#define STORAGE_VECENGINE_ENV_H_
+
+namespace vecengine {
+
+/* struct Options { */
+/*     std::string _db_location; */
+/*     size_t _mem_sync_interval; */
+/*     size_t _file_merge_trigger_number; */
+/*     size_t _index_file_build_trigger_size; */
+/* }; // Config */
+
+class Env {
+public:
+    Env() = default;
+
+private:
+    Options _option;
+}; // Env
+
+} //namespace vecengine
+
+#endif // STORAGE_VECENGINE_ENV_H_

cpp/src/options.h

+#ifndef VECENGINE_OPTIONS_H_
+#define VECENGINE_OPTIONS_H_
+
+namespace vecengine {
+
+struct Options {
+
+}; // Options
+
+} // namespace vecengine
+
+#endif // VECENGINE_OPTIONS_H_