+ /** @brief Create an MDB environment handle.
+ *
+ * This function allocates memory for a #MDB_env structure. To release
+ * the allocated memory and discard the handle, call #mdb_env_close().
+ * Before the handle may be used, it must be opened using #mdb_env_open().
+ * Various other options may also need to be set before opening the handle,
+ * e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(),
+ * depending on usage requirements.
+ * @param[out] env The address where the new handle will be stored
+ * @return A non-zero error value on failure and 0 on success.
+ */
+int mdb_env_create(MDB_env **env);
+
+ /** @brief Open an environment handle.
+ *
+ * If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle.
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[in] path The directory in which the database files reside. This
+ * directory must already exist and be writable.
+ * @param[in] flags Special options for this environment. This parameter
+ * must be set to 0 or by bitwise OR'ing together one or more of the
+ * values described here.
+ * <ul>
+ * <li>#MDB_FIXEDMAP
+ * use a fixed address for the mmap region. This flag must be specified
+ * when creating the environment, and is stored persistently in the environment.
+ * If successful, the memory map will always reside at the same virtual address
+ * and pointers used to reference data items in the database will be constant
+ * across multiple invocations. This option may not always work, depending on
+ * how the operating system has allocated memory to shared libraries and other uses.
+ * The feature is highly experimental.
+ * <li>#MDB_NOSUBDIR
+ * By default, MDB creates its environment in a directory whose
+ * pathname is given in \b path, and creates its data and lock files
+ * under that directory. With this option, \b path is used as-is for
+ * the database main data file. The database lock file is the \b path
+ * with "-lock" appended.
+ * <li>#MDB_NOSYNC
+ * Don't perform a synchronous flush after committing a transaction. This means
+ * transactions will exhibit the ACI (atomicity, consistency, and isolation)
+ * properties, but not D (durability); that is database integrity will be
+ * maintained but it is possible some number of the most recently committed
+ * transactions may be undone after a system crash. The number of transactions
+ * at risk is governed by how often the system flushes dirty buffers to disk
+ * and how often #mdb_env_sync() is called. This flag may be changed
+ * at any time using #mdb_env_set_flags().
+ * <li>#MDB_RDONLY
+ * Open the environment in read-only mode. No write operations will be allowed.
+ * </ul>
+ * @param[in] mode The UNIX permissions to set on created files. This parameter
+ * is ignored on Windows.
+ * @return A non-zero error value on failure and 0 on success. Some possible
+ * errors are:
+ * <ul>
+ * <li>#MDB_VERSION_MISMATCH - the version of the MDB library doesn't match the
+ * version that created the database environment.
+ * <li>EINVAL - the environment file headers are corrupted.
+ * <li>ENOENT - the directory specified by the path parameter doesn't exist.
+ * <li>EACCES - the user didn't have permission to access the environment files.
+ * <li>EAGAIN - the environment was locked by another process.
+ * </ul>
+ */
+int mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode);
+
+ /** @brief Return statistics about the MDB environment.
+ *
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[out] stat The address of an #MDB_stat structure
+ * where the statistics will be copied
+ */
+int mdb_env_stat(MDB_env *env, MDB_stat *stat);
+
+ /** @brief Flush the data buffers to disk.
+ *
+ * Data is always written to disk when #mdb_txn_commit() is called,
+ * but the operating system may keep it buffered. MDB always flushes
+ * the OS buffers upon commit as well, unless the environment was
+ * opened with #MDB_NOSYNC.
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[in] force If non-zero, force the flush to occur. Otherwise
+ * if the environment has the #MDB_NOSYNC flag set the flushes
+ * will be omitted.
+ * @return A non-zero error value on failure and 0 on success. Some possible
+ * errors are:
+ * <ul>
+ * <li>EINVAL - an invalid parameter was specified.
+ * <li>EIO - an error occurred during synchronization.
+ * </ul>
+ */
+int mdb_env_sync(MDB_env *env, int force);
+
+ /** @brief Close the environment and release the memory map.
+ *
+ * Only a single thread may call this function. All transactions, databases,
+ * and cursors must already be closed before calling this function. Attempts to
+ * use any such handles after calling this function will cause a SIGSEGV.
+ * The environment handle will be freed and must not be used again after this call.
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ */
+void mdb_env_close(MDB_env *env);
+
+ /** @brief Set environment flags.
+ *
+ * This may be used to set some flags that weren't already set during
+ * #mdb_env_open(), or to unset these flags. Currently only the
+ * #MDB_NOSYNC flag setting may be changed with this function.
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[in] flags The flags to change, bitwise OR'ed together
+ * @param[in] onoff A non-zero value sets the flags, zero clears them.
+ * @return A non-zero error value on failure and 0 on success. Some possible
+ * errors are:
+ * <ul>
+ * <li>EINVAL - an invalid parameter was specified.
+ * </ul>
+ */
+int mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff);