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// Copyright 2016 FullContact, Inc // Copyright 2017, 2018 Jason Lingle // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. use std::collections::HashSet; use std::ffi::{CStr, CString}; use std::mem; use std::ptr; use std::sync::Mutex; use libc::{self, c_char, c_int, c_uint, c_void}; use ffi; use ffi2; use tx::TxHandle; use ::{Fd, FileMode, Result}; /// Flags used when opening an LMDB environment. pub mod open { use libc; use ffi; bitflags! { /// Flags used when opening an LMDB environment. pub struct Flags : libc::c_uint { /// 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. const FIXEDMAP = ffi::MDB_FIXEDMAP; /// By default, LMDB creates its environment in a directory whose /// pathname is given in path, and creates its data and lock files /// under that directory. With this option, the `path` passed to /// `EnvBuilder::open` is used as-is for the database main data /// file. The database lock file is the path with "-lock" appended. const NOSUBDIR = ffi::MDB_NOSUBDIR; /// Open the environment in read-only mode. No write operations /// will be allowed. LMDB will still modify the lock file - except /// on read-only filesystems, where LMDB does not use locks. const RDONLY = ffi::MDB_RDONLY; /// Use a writeable memory map unless `RDONLY` is set. This is /// faster and uses fewer mallocs, but loses protection from /// application bugs like wild pointer writes and other bad updates /// into the database. Incompatible with nested transactions. Do /// not mix processes with and without `WRITEMAP` on the same /// environment. This can defeat durability (`Environment::sync` /// etc). const WRITEMAP = ffi::MDB_WRITEMAP; /// Flush system buffers to disk only once per transaction, omit /// the metadata flush. Defer that until the system flushes files /// to disk, or next non-`RDONLY` commit or `Environment::sync()`. /// This optimization maintains database integrity, but a system /// crash may undo the last committed transaction. I.e. it /// preserves the ACI (atomicity, consistency, isolation) but not D /// (durability) database property. This flag may be changed at any /// time using `Environment::set_flags()`. const NOMETASYNC = ffi::MDB_NOMETASYNC; /// Don't flush system buffers to disk when committing a /// transaction. This optimization means a system crash can corrupt /// the database or lose the last transactions if buffers are not /// yet flushed to disk. The risk is governed by how often the /// system flushes dirty buffers to disk and how often /// `Environment::sync()` is called. However, if the filesystem /// preserves write order and the `WRITEMAP` flag is not used, /// transactions exhibit ACI (atomicity, consistency, isolation) /// properties and only lose D (durability). I.e. database /// integrity is maintained, but a system crash may undo the final /// transactions. Note that `(NOSYNC | WRITEMAP)` leaves the system /// with no hint for when to write transactions to disk, unless /// `Environment::sync()` is called. `(MAPASYNC | WRITEMAP)` may be /// preferable. This flag may be changed at any time using /// `Environment::set_flags()`. const NOSYNC = ffi::MDB_NOSYNC; /// When using `WRITEMAP`, use asynchronous flushes to disk. As /// with `NOSYNC`, a system crash can then corrupt the database or /// lose the last transactions. Calling `Environment::sync()` /// ensures on-disk database integrity until next commit. This flag /// may be changed at any time using `Environment::set_flags()`. const MAPASYNC = ffi::MDB_MAPASYNC; /// Don't use Thread-Local Storage. Tie reader locktable slots to /// transaction objects instead of to threads. I.e. /// `Transaction::reset()` keeps the slot reseved for the /// transaction object. A thread may use parallel read-only /// transactions. A read-only transaction may span threads if the /// user synchronizes its use. Applications that multiplex many /// user threads over individual OS threads need this option. Such /// an application must also serialize the write transactions in an /// OS thread, since LMDB's write locking is unaware of the user /// threads. const NOTLS = ffi::MDB_NOTLS; /// Don't do any locking. If concurrent access is anticipated, the /// caller must manage all concurrency itself. For proper operation /// the caller must enforce single-writer semantics, and must /// ensure that no readers are using old transactions while a /// writer is active. The simplest approach is to use an exclusive /// lock so that no readers may be active at all when a writer /// begins. const NOLOCK = ffi::MDB_NOLOCK; /// Turn off readahead. Most operating systems perform readahead on /// read requests by default. This option turns it off if the OS /// supports it. Turning it off may help random read performance /// when the DB is larger than RAM and system RAM is full. The /// option is not implemented on Windows. const NORDAHEAD = ffi::MDB_NORDAHEAD; /// Don't initialize malloc'd memory before writing to unused /// spaces in the data file. By default, memory for pages written /// to the data file is obtained using malloc. While these pages /// may be reused in subsequent transactions, freshly malloc'd /// pages will be initialized to zeroes before use. This avoids /// persisting leftover data from other code (that used the heap /// and subsequently freed the memory) into the data file. Note /// that many other system libraries may allocate and free memory /// from the heap for arbitrary uses. E.g., stdio may use the heap /// for file I/O buffers. This initialization step has a modest /// performance cost so some applications may want to disable it /// using this flag. This option can be a problem for applications /// which handle sensitive data like passwords, and it makes memory /// checkers like Valgrind noisy. This flag is not needed with /// `WRITEMAP`, which writes directly to the mmap instead of using /// malloc for pages. The initialization is also skipped if /// `RESERVE` is used; the caller is expected to overwrite all of /// the memory that was reserved in that case. This flag may be /// changed at any time using `Environment::set_flags()`. const NOMEMINIT = ffi::MDB_NOMEMINIT; } } } /// Flags used when copying an LMDB environment. pub mod copy { use ffi2; use libc; bitflags! { /// Flags used when copying an LMDB environment. pub struct Flags : libc::c_uint { /// Perform compaction while copying: omit free pages and sequentially /// renumber all pages in output. This option consumes more CPU and /// runs more slowly than the default. const COMPACT = ffi2::MDB_CP_COMPACT; } } } #[derive(Debug)] struct EnvHandle(*mut ffi::MDB_env, bool); unsafe impl Sync for EnvHandle { } unsafe impl Send for EnvHandle { } impl Drop for EnvHandle { fn drop(&mut self) { if self.1 { unsafe { ffi::mdb_env_close(self.0) } } } } /// Handle on an uninitialised LMDB environment to allow configuring pre-open /// options. #[derive(Debug)] pub struct EnvBuilder { env: EnvHandle, } impl EnvBuilder { /// Allocates a new, uninitialised environment. pub fn new() -> Result<Self> { let mut env: *mut ffi::MDB_env = ptr::null_mut(); unsafe { lmdb_call!(ffi::mdb_env_create(&mut env)); Ok(EnvBuilder { env: EnvHandle(env, true) }) } } /// Set the size of the memory map to use for this environment. /// /// The size should be a multiple of the OS page size. The default is /// 10485760 bytes. The size of the memory map is also the maximum size of /// the database. The value should be chosen as large as possible, to /// accommodate future growth of the database. /// /// The new size takes effect immediately for the current process but will /// not be persisted to any others until a write transaction has been /// committed by the current process. Also, only mapsize increases are /// persisted into the environment. /// /// See also `Environment::set_mapsize()`. pub fn set_mapsize(&mut self, size: usize) -> Result<()> { unsafe { lmdb_call!(ffi::mdb_env_set_mapsize( self.env.0, size as libc::size_t)); } Ok(()) } /// Set the maximum number of threads/reader slots for the environment. /// /// This defines the number of slots in the lock table that is used to /// track readers in the the environment. The default is 126. Starting a /// read-only transaction normally ties a lock table slot to the current /// thread until the environment closes or the thread exits. If `NOTLS` is /// in use, starting a transaction instead ties the slot to the transaction /// object until it or the `Environment` object is destroyed. pub fn set_maxreaders(&mut self, readers: u32) -> Result<()> { unsafe { lmdb_call!(ffi::mdb_env_set_maxreaders( self.env.0, readers as libc::c_uint)); } Ok(()) } /// Set the maximum number of named databases for the environment. /// /// This function is only needed if multiple databases will be used in the /// environment. Simpler applications that use the environment as a single /// unnamed database can ignore this option. /// /// Currently a moderate number of slots are cheap but a huge number gets /// expensive: 7-120 words per transaction, and every mdb_dbi_open() does a /// linear search of the opened slots. pub fn set_maxdbs(&mut self, dbs: u32) -> Result<()> { unsafe { lmdb_call!(ffi::mdb_env_set_maxdbs( self.env.0, dbs as libc::c_uint)); } Ok(()) } /// Opens the file or directory at `path` with the given `flags` and, on /// UNIX, permissions given by `mode`. /// /// `path` is a `&str` for convenience, and must be convertable to a /// `CString`. The non-use of `&OsStr` or `AsRef<Path>` as normally used in /// `std` is deliberate, since the path must be convertable to a byte /// string. But as a result there is no way to address files whose names /// are not valid UTF-8 through this call. /// /// ## Unsafety /// /// It is the caller's responsibility to ensure that the underlying file /// will be used properly. Since LMDB is built on memory-mapping, these /// responsibilities run quite deep and vary based on `flags`. /// /// - The caller must ensure that no other process writes to the file in /// any way except going through LMDB. If this is violated, segfaults can /// occur, or immutable references can be observed to have their referent /// mutated asynchronously. /// /// - If the caller uses flags which suppress locking, the caller must /// additionally ensure that LMDB's locking requirements are upheld. /// /// - If the caller uses flags that result in the creation of a sparse /// file, the caller must ensure there is actually sufficient disk space /// for all pages of the file or else a segfault may occur. pub unsafe fn open(self, path: &str, flags: open::Flags, mode: FileMode) -> Result<Environment> { let path_cstr = try!(CString::new(path)); lmdb_call!(ffi::mdb_env_open( self.env.0, path_cstr.as_ptr(), flags.bits(), mode)); Ok(Environment { env: self.env, open_dbis: Mutex::new(HashSet::new()), }) } } /// An LMDB environment which has been opened to a file. #[derive(Debug)] pub struct Environment { env: EnvHandle, // Track what DBIs are currently in use, so that an open() call that tries // to duplicate one fails. open_dbis: Mutex<HashSet<ffi::MDB_dbi>>, } /// Statistics information about an environment. #[derive(Debug,Clone,Copy)] pub struct Stat { /// Size of a database page. This is currently the same for all databases. pub psize: u32, /// Depth (height) of the B-tree pub depth: u32, /// Number of internal (non-leaf) pages pub branch_pages: usize, /// Number of leaf pages pub leaf_pages: usize, /// Number of overflow pages pub overflow_pages: usize, /// Number of data items pub entries: usize, } impl From<ffi::MDB_stat> for Stat { fn from(raw: ffi::MDB_stat) -> Stat { Stat { psize: raw.ms_psize as u32, depth: raw.ms_depth as u32, branch_pages: raw.ms_branch_pages as usize, leaf_pages: raw.ms_leaf_pages as usize, overflow_pages: raw.ms_overflow_pages as usize, entries: raw.ms_entries as usize, } } } /// Configuration information about an environment. #[derive(Debug,Clone,Copy)] pub struct EnvInfo { /// Address of map, if fixed pub mapaddr: *const c_void, /// Size of the data memory map pub mapsize: usize, /// ID of the last used page pub last_pgno: usize, /// ID of the last committed transaction pub last_txnid: usize, /// max reader slots in the environment pub maxreaders: u32, /// max reader slots used in the environment pub numreaders: u32, } impl Environment { /// Wrap a raw LMDB environment handle in an `Environment`. /// /// The `Environment` assumes ownership of the `MDB_env`. If you do not /// want this, see [`borrow_raw()`](#method.borrow_raw) instead. /// /// ## Unsafety /// /// `env` must point to a valid `MDB_env`. /// /// It is the caller's responsibility to ensure that nothing destroys the /// `MDB_env` before [`into_raw()`](#method.into_raw) is called, and that /// nothing attempts to use the `MDB_env` after `Environment` is dropped /// normally. /// /// It is safe for multiple `Environment`s bound to the same `MDB_env` to /// coexist (though the others would need to be created by `borrow_raw`). /// However, care must be taken when using databases since by default the /// `Environment` will assume ownership of those as well. pub unsafe fn from_raw(env: *mut ffi::MDB_env) -> Self { Environment { env: EnvHandle(env, true), open_dbis: Mutex::new(HashSet::new()), } } /// Wrap a raw LMDB environment handle in an `Environment` without taking /// ownership. /// /// The `Environment` does not assume ownership of the `MDB_env`, and will /// not destroy it when it is dropped. See [`from_raw()`](#method.from_raw) /// if taking ownership is desired. /// /// Note that this does not affect assumed ownership of `MDB_dbi` handles; /// databases opened by `Database::open` are still presumed owned. /// /// ## Unsafety /// /// `env` must point to a valid `MDB_env`. /// /// It is safe for multiple `Environment`s bound to the same `MDB_env` to /// coexist (though the others would need to be created by `borrow_raw`). /// However, care must be taken when using databases since by default the /// `Environment` will assume ownership of those as well. pub unsafe fn borrow_raw(env: *mut ffi::MDB_env) -> Self { Environment { env: EnvHandle(env, false), open_dbis: Mutex::new(HashSet::new()), } } /// Return the underlying `MDB_env` handle. /// /// ## Safety /// /// While this call is in and of itself safe, the caller must ensure that /// operations against the backing store do not violate Rust aliasing /// rules, and must not take any action that would cause the `MDB_env` to /// be destroyed prematurely, or to use it after this `Environment` is /// destroyed. pub fn as_raw(&self) -> *mut ffi::MDB_env { self.env.0 } /// Consume this `Environment` and return the underlying handle. /// /// After this call, it is the caller's responsibility to ensure that the /// `MDB_env` is eventually destroyed, if it was actually owned by this /// `Environment` (compare [`from_raw`](#method.from_raw) and /// [`borrow_raw`](#method.borrow_raw)). /// /// ## Safety /// /// While this call is in and of itself safe, the caller must ensure that /// operations against the backing store do not violate Rust aliasing /// rules. pub fn into_raw(self) -> *mut ffi::MDB_env { let ret = self.env.0; mem::forget(self.env); ret } /// Copy an LMDB environment to the specified path, with options. /// /// This function may be used to make a backup of an existing environment. /// No lockfile is created, since it gets recreated at need. /// /// ## Note /// /// This call can trigger significant file size growth if run in parallel /// with write transactions, because it employs a read-only transaction. /// See long-lived transactions under Caveats. /// /// ## Example /// /// ``` /// # include!(concat!(env!("CARGO_MANIFEST_DIR"),"/src/example_helpers.rs")); /// # fn main() { /// # let env = create_env(); /// let out = tempdir::TempDir::new_in(".", "lmdbcopy").unwrap(); /// env.copy(out.path().to_str().unwrap(), /// lmdb::copy::COMPACT).unwrap(); /// // We could now open up an independent environment in `lmdbcopyXXXX` /// // or upload it somewhere, eg, while `env` could continue being /// // modified concurrently. /// # } /// ``` pub fn copy(&self, path: &str, flags: copy::Flags) -> Result<()> { let path_cstr = try!(CString::new(path)); unsafe { lmdb_call!(ffi2::mdb_env_copy2( self.env.0, path_cstr.as_ptr(), flags.bits())); } Ok(()) } /// Copy an LMDB environment to the specified file descriptor, with options. /// /// This function may be used to make a backup of an existing environment. /// No lockfile is created, since it gets recreated at need. See /// `copy()` for further details. /// /// ## Note /// /// This call can trigger significant file size growth if run in parallel /// with write transactions, because it employs a read-only transaction. /// See long-lived transactions under Caveats. pub fn copyfd(&self, fd: Fd, flags: copy::Flags) -> Result<()> { unsafe { lmdb_call!(ffi2::mdb_env_copyfd2(self.env.0, fd, flags.bits())); } Ok(()) } /// Return statistics about the LMDB environment. pub fn stat(&self) -> Result<Stat> { let raw = unsafe { let mut raw = mem::zeroed::<ffi::MDB_stat>(); lmdb_call!(ffi::mdb_env_stat(self.env.0, &mut raw)); raw }; Ok(raw.into()) } /// Return information about the LMDB environment. pub fn info(&self) -> Result<EnvInfo> { let raw = unsafe { let mut raw = mem::zeroed::<ffi::MDB_envinfo>(); lmdb_call!(ffi::mdb_env_info(self.env.0, &mut raw)); raw }; Ok(EnvInfo { mapaddr: raw.me_mapaddr as *const c_void, mapsize: raw.me_mapsize as usize, last_pgno: raw.me_last_pgno as usize, last_txnid: raw.me_last_txnid as usize, maxreaders: raw.me_maxreaders as u32, numreaders: raw.me_numreaders as u32, }) } /// Flush the data buffers to disk. /// /// Data is always written to disk when transactions are committed, but the /// operating system may keep it buffered. LMDB always flushes the OS /// buffers upon commit as well, unless the environment was opened with /// `NOSYNC` or in part `NOMETASYNC`. This call is not valid if the /// environment was opened with `RDONLY`. /// /// If `force` is true, force a synchronous flush. Otherwise if the /// environment has the `NOSYNC` flag set the flushes will be omitted, and /// with `MAPASYNC` they will be asynchronous. pub fn sync(&self, force: bool) -> Result<()> { unsafe { lmdb_call!(ffi::mdb_env_sync(self.env.0, force as c_int)); } Ok(()) } /// Set environment flags. /// /// This may be used to set some flags in addition to those from /// `EnvBuilder::open()`, or to unset these flags. If several threads /// change the flags at the same time, the result is undefined. /// /// `flags` specifies the flags to edit, not the new status of all flags. /// If `onoff` is true, all flags in `flags` are set; otherwise, all flags /// in `flags` are cleared. /// /// ## Unsafety /// /// The caller must ensure that multiple threads do not call this /// concurrently with itself or with `get_flags()`. This could not be /// accomplished by using `&mut self`, since any open databases necessarily /// have the environment borrowed already. /// /// ## Example /// ``` /// # include!(concat!(env!("CARGO_MANIFEST_DIR"),"/src/example_helpers.rs")); /// # fn main() { /// # let env = create_env(); /// unsafe { /// // Enable the NOMETASYNC and MAPASYNC flags /// env.set_flags(lmdb::open::NOMETASYNC | lmdb::open::MAPASYNC, true) /// .unwrap(); /// assert!(env.flags().unwrap().contains( /// lmdb::open::NOMETASYNC | lmdb::open::MAPASYNC)); /// // Turn MAPASYNC back off, leaving NOMETASYNC set /// env.set_flags(lmdb::open::MAPASYNC, false).unwrap(); /// assert!(env.flags().unwrap().contains(lmdb::open::NOMETASYNC)); /// assert!(!env.flags().unwrap().contains(lmdb::open::MAPASYNC)); /// } /// # } /// ``` pub unsafe fn set_flags(&self, flags: open::Flags, onoff: bool) -> Result<()> { lmdb_call!(ffi::mdb_env_set_flags( self.env.0, flags.bits(), onoff as c_int)); Ok(()) } /// Get environment flags. pub fn flags(&self) -> Result<open::Flags> { let mut raw: c_uint = 0; unsafe { lmdb_call!(ffi::mdb_env_get_flags(self.env.0, &mut raw)); } Ok(open::Flags::from_bits_truncate(raw)) } /// Return the path that was used in `EnvBuilder::open()`. /// /// ## Panics /// /// Panics if LMDB returns success but sets the path to a NULL pointer. pub fn path(&self) -> Result<&CStr> { let mut raw: *mut c_char = ptr::null_mut(); unsafe { lmdb_call!(ffi::mdb_env_get_path(self.env.0, &mut raw)); if raw.is_null() { panic!("mdb_env_get_path() returned NULL pointer"); } Ok(CStr::from_ptr(raw)) } } /// Return the filedescriptor for the given environment. /// /// ## Unsafety /// /// The caller must ensure that the file descriptor is not used to subvert /// normal LMDB functionality, such as by writing to it or closing it. pub unsafe fn fd(&self) -> Result<Fd> { let mut raw: Fd = 0; lmdb_call!(ffi::mdb_env_get_fd(self.env.0, &mut raw)); Ok(raw) } /// Set the size of the memory map to use for this environment. /// /// The size should be a multiple of the OS page size. The default is /// 10485760 bytes. The size of the memory map is also the maximum size of /// the database. The value should be chosen as large as possible, to /// accommodate future growth of the database. /// /// The new size takes effect immediately for the current process but will /// not be persisted to any others until a write transaction has been /// committed by the current process. Also, only mapsize increases are /// persisted into the environment. /// /// If the mapsize is increased by another process, and data has grown /// beyond the range of the current mapsize, starting a transaction will /// return `error::MAP_RESIZED`. This function may be called with a size of /// zero to adopt the new size. /// /// ## Unsafety /// /// This may only be called if no transactions are active in the current /// process. Note that the library does not check for this condition, the /// caller must ensure it explicitly. pub unsafe fn set_mapsize(&self, size: usize) -> Result<()> { lmdb_call!(ffi::mdb_env_set_mapsize(self.env.0, size)); Ok(()) } /// Get the maximum number of threads/reader slots for the environment. pub fn maxreaders(&self) -> Result<u32> { let mut raw: c_uint = 0; unsafe { lmdb_call!(ffi::mdb_env_get_maxreaders(self.env.0, &mut raw)); } Ok(raw as u32) } /// Get the maximum size of keys and `DUPSORT` data we can write. /// /// Depends on the compile-time constant `MDB_MAXKEYSIZE` in LMDB. /// Default 511. pub fn maxkeysize(&self) -> u32 { unsafe { ffi::mdb_env_get_maxkeysize(self.env.0) as u32 } } /// Check for stale entries in the reader lock table. /// /// Returns the number of stale slots that were cleared. pub fn reader_check(&self) -> Result<i32> { let mut raw: c_int = 0; unsafe { lmdb_call!(ffi::mdb_reader_check(self.env.0, &mut raw)); } Ok(raw as i32) } } // Internal API pub fn dbi_close(this: &Environment, dbi: ffi::MDB_dbi) { // Hold the lock through the end of the function to also guard the // LMDB's unsynchronised DBI table. let mut locked_dbis = this.open_dbis.lock() .expect("open_dbis lock poisoned"); assert!(locked_dbis.remove(&dbi), "closed dbi that wasn't open"); unsafe { ffi::mdb_dbi_close(this.env.0, dbi); } } // Internal API pub fn dbi_delete(this: &Environment, dbi: ffi::MDB_dbi) -> Result<()> { // Hold the lock across the call to `mdb_drop()` to also guard its // unsynchronised DBI table. let mut locked_dbis = this.open_dbis.lock() .expect("open_dbis lock poisoned"); unsafe { let mut raw_txn: *mut ffi::MDB_txn = ptr::null_mut(); lmdb_call!(ffi::mdb_txn_begin( this.env.0, ptr::null_mut(), 0, &mut raw_txn)); let mut txn = TxHandle(raw_txn); lmdb_call!(ffi::mdb_drop(raw_txn, dbi, 1 /* delete */)); try!(txn.commit()); } assert!(locked_dbis.remove(&dbi), "closed dbi that wasn't open"); Ok(()) } // Internal API pub fn env_ptr(this: &Environment) -> *mut ffi::MDB_env { this.env.0 } // Internal API pub fn env_open_dbis(this: &Environment) -> &Mutex<HashSet<ffi::MDB_dbi>> { &this.open_dbis } #[cfg(test)] mod test { use test_helpers::*; use env::*; use tx::*; #[test] fn borrow_raw_doesnt_take_ownership() { let outer_env = create_env(); { let inner_env = unsafe { Environment::borrow_raw(outer_env.as_raw()) }; let db = defdb(&inner_env); let tx = WriteTransaction::new(&inner_env).unwrap(); tx.access().put(&db, "foo", "bar", put::Flags::empty()).unwrap(); tx.commit().unwrap(); } let db = defdb(&outer_env); let tx = ReadTransaction::new(&outer_env).unwrap(); assert_eq!("bar", tx.access().get::<str,str>(&db, "foo").unwrap()); } }