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216 lines
8.0 KiB
216 lines
8.0 KiB
use libc::{c_uint, size_t, mode_t};
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use std::io::FilePermission;
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use std::ptr;
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use error::{LmdbError, LmdbResult, lmdb_result};
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use ffi;
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use ffi::MDB_env;
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use flags::EnvironmentFlags;
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use transaction::Transaction;
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/// An LMDB environment.
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///
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/// An environment supports multiple databases, all residing in the same shared-memory map.
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pub struct Environment {
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env: *mut MDB_env,
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}
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impl Environment {
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/// Creates a new builder for specifying options for opening an LMDB environment.
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pub fn new() -> EnvironmentBuilder {
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EnvironmentBuilder {
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flags: EnvironmentFlags::empty(),
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max_readers: None,
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max_dbs: None,
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map_size: None
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}
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}
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/// Returns a raw pointer to the underlying LMDB environment.
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///
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/// The caller **must** ensure that the pointer is not dereferenced after the lifetime of the
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/// environment.
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pub fn env(&self) -> *mut MDB_env {
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self.env
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}
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/// Create a transaction for use with the environment.
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///
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/// `flags` must either be empty, or `MDB_RDONLY` in order to specify a read-only transaction.
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pub fn begin_txn<'a>(&'a self, flags: EnvironmentFlags) -> LmdbResult<Transaction<'a>> {
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Transaction::new(self, flags)
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}
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/// Flush data buffers to disk.
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///
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/// Data is always written to disk when `Transaction::commit()` is called, but the operating
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/// system may keep it buffered. LMDB always flushes the OS buffers upon commit as well, unless
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/// the environment was opened with `MDB_NOSYNC` or in part `MDB_NOMETASYNC`.
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pub fn sync(&self, force: bool) -> LmdbResult<()> {
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unsafe {
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lmdb_result(ffi::mdb_env_sync(self.env(), if force { 1 } else { 0 }))
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}
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}
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}
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impl Drop for Environment {
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fn drop(&mut self) {
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unsafe { ffi::mdb_env_close(self.env) }
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}
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}
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///////////////////////////////////////////////////////////////////////////////////////////////////
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//// Environment Builder
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///////////////////////////////////////////////////////////////////////////////////////////////////
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/// Options for opening or creating an environment.
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#[deriving(Show, PartialEq, Eq)]
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pub struct EnvironmentBuilder {
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flags: EnvironmentFlags,
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max_readers: Option<c_uint>,
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max_dbs: Option<c_uint>,
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map_size: Option<size_t>,
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}
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impl EnvironmentBuilder {
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/// Open an environment.
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pub fn open(&self, path: &Path, mode: FilePermission) -> LmdbResult<Environment> {
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let mut env: *mut MDB_env = ptr::null_mut();
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unsafe {
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lmdb_try!(ffi::mdb_env_create(&mut env));
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if let Some(max_readers) = self.max_readers {
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lmdb_try_with_cleanup!(ffi::mdb_env_set_maxreaders(env, max_readers),
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ffi::mdb_env_close(env))
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}
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if let Some(max_dbs) = self.max_dbs {
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lmdb_try_with_cleanup!(ffi::mdb_env_set_maxdbs(env, max_dbs),
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ffi::mdb_env_close(env))
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}
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if let Some(map_size) = self.map_size {
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lmdb_try_with_cleanup!(ffi::mdb_env_set_mapsize(env, map_size),
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ffi::mdb_env_close(env))
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}
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lmdb_try_with_cleanup!(ffi::mdb_env_open(env,
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path.to_c_str().as_ptr(),
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self.flags.bits(),
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mode.bits() as mode_t),
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ffi::mdb_env_close(env));
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}
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Ok(Environment { env: env })
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}
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pub fn set_flags(&mut self, flags: EnvironmentFlags) -> &mut EnvironmentBuilder {
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self.flags = flags;
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self
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}
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/// Sets the maximum number of threads or reader slots for the environment.
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///
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/// This defines the number of slots in the lock table that is used to track readers in the
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/// the environment. The default is 126. Starting a read-only transaction normally ties a lock
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/// table slot to the current thread until the environment closes or the thread exits. If
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/// `MDB_NOTLS` is in use, `Environment::open_txn` instead ties the slot to the `Transaction`
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/// object until it or the `Environment` object is destroyed.
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pub fn set_max_readers(&mut self, max_readers: c_uint) -> &mut EnvironmentBuilder {
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self.max_readers = Some(max_readers);
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self
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}
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/// Sets the maximum number of named databases for the environment.
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///
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/// This function is only needed if multiple databases will be used in the
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/// environment. Simpler applications that use the environment as a single
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/// unnamed database can ignore this option.
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///
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/// Currently a moderate number of slots are cheap but a huge number gets
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/// expensive: 7-120 words per transaction, and every `Transaction::open_db`
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/// does a linear search of the opened slots.
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pub fn set_max_dbs(&mut self, max_readers: c_uint) -> &mut EnvironmentBuilder {
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self.max_dbs = Some(max_readers);
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self
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}
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/// Sets the size of the memory map to use for the environment.
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///
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/// The size should be a multiple of the OS page size. The default is
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/// 10485760 bytes. The size of the memory map is also the maximum size
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/// of the database. The value should be chosen as large as possible,
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/// to accommodate future growth of the database. It may be increased at
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/// later times.
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///
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/// Any attempt to set a size smaller than the space already consumed
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/// by the environment will be silently changed to the current size of the used space.
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pub fn set_map_size(&mut self, map_size: size_t) -> &mut EnvironmentBuilder {
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self.map_size = Some(map_size);
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self
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}
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}
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#[cfg(test)]
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mod test {
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use std::io;
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use flags;
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use super::*;
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#[test]
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fn test_open() {
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let dir = io::TempDir::new("test").unwrap();
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// opening non-existent env with read-only should fail
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assert!(Environment::new().set_flags(flags::MDB_RDONLY)
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.open(dir.path(), io::USER_RWX)
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.is_err());
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// opening non-existent env should not fail
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assert!(Environment::new().open(dir.path(), io::USER_RWX).is_ok());
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// opening env with read-only should not fail
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assert!(Environment::new().set_flags(flags::MDB_RDONLY)
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.open(dir.path(), io::USER_RWX)
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.is_ok());
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}
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#[test]
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fn test_begin_txn() {
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let dir = io::TempDir::new("test").unwrap();
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let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
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{
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// Mutable env, mutable txn
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assert!(env.begin_txn(flags::EnvironmentFlags::empty()).is_ok());
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} {
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// Mutable env, read-only txn
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assert!(env.begin_txn(flags::MDB_RDONLY).is_ok());
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} {
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// Read-only env, mutable txn
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let env = Environment::new().set_flags(flags::MDB_RDONLY)
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.open(dir.path(), io::USER_RWX)
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.unwrap();
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assert!(env.begin_txn(flags::EnvironmentFlags::empty()).is_err());
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} {
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// Read-only env, read-only txn
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let env = Environment::new().set_flags(flags::MDB_RDONLY)
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.open(dir.path(), io::USER_RWX)
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.unwrap();
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assert!(env.begin_txn(flags::MDB_RDONLY).is_ok());
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}
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}
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#[test]
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fn test_sync() {
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let dir = io::TempDir::new("test").unwrap();
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{
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let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
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assert!(env.sync(true).is_ok());
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} {
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let env = Environment::new().set_flags(flags::MDB_RDONLY)
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.open(dir.path(), io::USER_RWX)
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.unwrap();
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assert!(env.sync(true).is_ok());
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}
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}
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}
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