Struct mmtkvdb::EnvBuilder

pub struct EnvBuilder<P> { /* private fields */ }

Options for opening an environment

This struct follows the builder pattern. Start with EnvBuilder::new and open the environment with EnvBuilder::open_ro (for read-only access) or EnvBuilder::open_rw (for read-write access).

Caveats / Safety

Do not open the same environment twice in the same process.

Since this cannot be easily ensured (and because the environment must be free of corruption on the storage medium), open_ro and open_rw are marked as unsafe. Use EnvRo::clone to (re-)open an already open environment in read-only mode.

The file format is platform specific, so endianness and word size must not change across use.

Example

// question mark operator may return with `std::io::Error`
use mmtkvdb::{self as kv, Txn as _};
use tempfile::tempdir;
let location = tempdir()?;
let env_builder = kv::EnvBuilder::new().dir(location.path()).max_dbs(1);
let mut env_rw = unsafe { env_builder.open_rw() }?;
let env_ro = env_rw.clone(); // clones `EnvRo` due to deref coercion

Implementations

impl EnvBuilder<()>

pub const fn new() -> Self

Default options for environment

impl<P> EnvBuilder<P>

pub fn dir<'a>(self, path: &'a impl AsRef<Path> + ?Sized) -> EnvBuilder<&'a Path>

Set directory location

pub fn file<'a>(
    self,
    path: &'a impl AsRef<Path> + ?Sized
) -> EnvBuilder<&'a Path>

Set file location

pub const fn get_writemap(&self) -> bool

Get writable memory map option

pub const fn writemap(self, flag: bool) -> Self

Set or clear writable memory map option

Enabling the writable memory map is incompatible with nested transactions (see TxnRw::nested).

pub const fn get_nometasync(&self) -> bool

Get no-meta-sync option

pub const fn nometasync(self, flag: bool) -> Self

Set or clear no-meta-sync option

pub const fn get_max_size(&self) -> usize

Get maximum environment size

pub const fn max_size(self, max_size: usize) -> Self

Set maximum environment size

pub const fn get_max_readers(&self) -> usize

Get maximum number of concurrent readers

pub const fn max_readers(self, max_readers: usize) -> Self

Set maximum number of concurrent readers

pub const fn get_max_dbs(&self) -> usize

Get maximum number of named databases

pub const fn max_dbs(self, max_dbs: usize) -> Self

Set maximum number of named databases

pub const fn get_unix_file_mode(&self) -> u32

Get file mode

pub const fn unix_file_mode(self, mode: u32) -> Self

Set file mode

pub const fn nestable_txns(&self) -> bool

Check if transactions are nestable with current options

See TxnRw::nested.

impl<'a> EnvBuilder<&'a Path>

pub unsafe fn open_ro(&self) -> Result<EnvRo>

Open environment in read-only mode

Safety

• Do not open the same environment twice in the same process.
• The environment must be free of corruption on the storage medium.
• The file format is platform specific, so endianness and word size must not change across use.

pub unsafe fn open_rw(&self) -> Result<EnvRw>

Open environment in read-write mode

Safety

• Do not open the same environment twice in the same process.
• The environment must be free of corruption on the storage medium.
• The file format is platform specific, so endianness and word size must not change across use.

Trait Implementations

impl<P: Clone> Clone for EnvBuilder<P>

fn clone(&self) -> EnvBuilder<P>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<P: Debug> Debug for EnvBuilder<P>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.