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// Copyright 2016 FullContact, Inc // // 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::cell::Cell; use std::mem; use std::ops::{Deref, DerefMut}; use std::ptr; use libc::c_uint; use ffi; use ffi2; use env::{self, Environment, Stat}; use dbi::{db, Database}; use error::{Error, Result}; use mdb_vals::*; use traits::*; use cursor::{self, Cursor, StaleCursor}; /// Flags used when calling the various `put` functions. pub mod put { use ffi; use libc; bitflags! { /// Flags used when calling the various `put` functions. /// /// Note that `RESERVE` and `MULTIPLE` are not exposed in these flags /// because their memory ownership and/or parameter semantics are /// different. `CURRENT` is expressed separately on the cursor /// functions. pub flags Flags : libc::c_uint { /// Enter the new key/data pair only if it does not already appear /// in the database. This flag may only be specified if the /// database was opened with `DUPSORT`. The function will return /// `KEYEXIST` if the key/data pair already appears in the /// database. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("reversed"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// // Duplicate, but that's OK by default /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// // `NODUPDATA` blocks adding an identical item /// assert!(access.put(&db, "Fruit", "Apple", lmdb::put::NODUPDATA).is_err()); /// // But doesn't affect pairs not already present /// access.put(&db, "Fruit", "Durian", lmdb::put::NODUPDATA).unwrap(); /// } /// txn.commit().unwrap(); /// # } /// ``` /// /// When used on a cursor, the cursor is positioned at the /// conflicting key/value pair if this results in a `KEYEXIST` /// error. /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("reversed"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Durian", lmdb::put::Flags::empty()).unwrap(); /// /// let mut cursor = txn.cursor(&db).unwrap(); /// assert_eq!(Err(lmdb::Error::Code(lmdb::error::KEYEXIST)), /// cursor.put(&mut access, "Fruit", "Durian", /// lmdb::put::NODUPDATA)); /// assert_eq!(("Fruit", "Durian"), cursor.get_current(&access).unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` const NODUPDATA = ffi::MDB_NODUPDATA, /// Enter the new key/data pair only if the key does not already /// appear in the database. The function will return `KEYEXIST` if /// the key already appears in the database, even if the database /// supports duplicates (`DUPSORT`). /// /// ## Examples /// /// ### In a 1:1 database /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, None, &lmdb::DatabaseOptions::defaults()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// // By default, collisions overwrite the old value /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// assert_eq!("Orange", access.get::<str,str>(&db, "Fruit").unwrap()); /// // But `NOOVERWRITE` prevents that /// assert!(access.put(&db, "Fruit", "Durian", lmdb::put::NOOVERWRITE).is_err()); /// assert_eq!("Orange", access.get::<str,str>(&db, "Fruit").unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` /// /// ### In a `DUPSORT` database /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("reversed"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// // Ordinarily, we can add multiple items per key /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// let mut cursor = txn.cursor(&db).unwrap(); /// cursor.seek_k::<str,str>(&access, "Fruit").unwrap(); /// assert_eq!(2, cursor.count().unwrap()); /// /// // But this can be prevented with `NOOVERWRITE` /// access.put(&db, "Veggie", "Carrot", lmdb::put::NOOVERWRITE).unwrap(); /// assert!(access.put(&db, "Veggie", "Squash", lmdb::put::NOOVERWRITE).is_err()); /// cursor.seek_k::<str,str>(&access, "Veggie").unwrap(); /// assert_eq!(1, cursor.count().unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` // TODO: "The data parameter will be set to point to the existing // item." We should provide functionality to support that. const NOOVERWRITE = ffi::MDB_NOOVERWRITE, /// Append the given key/data pair to the end of the database. This /// option allows fast bulk loading when keys are already known to /// be in the correct order. Loading unsorted keys with this flag /// will cause a `KEYEXIST` error. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, None, &lmdb::DatabaseOptions::defaults()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// // Load values in ascending order /// access.put(&db, "France", "Paris", lmdb::put::APPEND).unwrap(); /// access.put(&db, "Germany", "Berlin", lmdb::put::APPEND).unwrap(); /// access.put(&db, "Latvia", "Rīga", lmdb::put::APPEND).unwrap(); /// // Error if you violate ordering /// assert!(access.put(&db, "Armenia", "Yerevan", lmdb::put::APPEND) /// .is_err()); /// } /// txn.commit().unwrap(); /// # } /// ``` const APPEND = ffi::MDB_APPEND, /// As with `APPEND` above, but for sorted dup data. const APPENDDUP = ffi::MDB_APPENDDUP, } } } /// Flags used when deleting items. pub mod del { use ffi; use libc; bitflags! { /// Flags used when deleting items via cursors. pub flags Flags : libc::c_uint { /// Delete all of the data items for the current key instead of /// just the current item. This flag may only be specified if the /// database was opened with `DUPSORT`. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("reversed"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// let f = lmdb::put::Flags::empty(); /// access.put(&db, "Fruit", "Apple", f).unwrap(); /// access.put(&db, "Fruit", "Orange", f).unwrap(); /// access.put(&db, "Fruit", "Durian", f).unwrap(); /// /// let mut cursor = txn.cursor(&db).unwrap(); /// cursor.seek_kv("Fruit", "Durian").unwrap(); /// // By default, only the current item is deleted. /// cursor.del(&mut access, lmdb::del::Flags::empty()).unwrap(); /// cursor.seek_k::<str,str>(&access, "Fruit").unwrap(); /// assert_eq!(2, cursor.count().unwrap()); /// // But with `NODUPDATA`, they will all go away /// cursor.del(&mut access, lmdb::del::NODUPDATA).unwrap(); /// assert!(cursor.seek_k::<str,str>(&access, "Fruit").is_err()); /// } /// txn.commit().unwrap(); /// # } /// ``` const NODUPDATA = ffi::MDB_NODUPDATA, } } } // This is internal, but used by other parts of the library #[derive(Debug)] pub struct TxHandle(pub *mut ffi::MDB_txn); impl Drop for TxHandle { fn drop(&mut self) { if !self.0.is_null() { unsafe { ffi::mdb_txn_abort(self.0); } self.0 = ptr::null_mut(); } } } impl TxHandle { pub unsafe fn commit(&mut self) -> Result<()> { let txn_p = mem::replace(&mut self.0, ptr::null_mut()); lmdb_call!(ffi::mdb_txn_commit(txn_p)); Ok(()) } } /// Base functionality for an LMDB transaction. /// /// The type is "const" in a similar usage to the modifier in C: One cannot use /// it to make any modifications, but also cannot rely on it actually being /// read-only. `ConstTransaction`s are used to write code that can operate in /// either kind of transaction. /// /// Unlike most other LMDB wrappers, transactions here are (indirectly) the /// things in control of accessing data behind cursors. This is in order to /// correctly express memory semantics: Moving a cursor does not invalidate /// memory obtained from the cursor; however, any mutation through the same /// transaction does. We therefore model accesses to data in the environment as /// borrows of the transaction and the database themselves (possibly mutable on /// the latter), which allows the borrow checker to ensure that all references /// are dropped before doing a structural modification. /// /// Note that due to limitations in the Rust borrow checker, one actually needs /// to use the `*Accessor` structs to access data. Any transaction will yield /// at most one accessor, which is implemented with a runtime check that should /// in the vast majority of cases get optimised out. /// /// Mutability of a transaction reference does not indicate mutability of the /// underlying database, but rather exclusivity for enforcement of child /// transaction semantics. /// /// ## Lifetime /// /// A `ConstTransaction` must be strictly outlived by its `Environment`. /// /// `'env` is covariant: given two lifetimes `'x` and `'y` where `'x: 'y`, a /// `&ConstTransaction<'x>` will implicitly coerce to `&ConstTransaction<'y>`. /// /// ```rust,norun /// # #![allow(dead_code)] /// # extern crate lmdb_zero as lmdb; /// # fn main() { } /// # /// fn convariance<'x, 'y>(db: &lmdb::ConstTransaction<'x>) /// where 'x: 'y { /// let _db2: &lmdb::ConstTransaction<'y> = db; /// } /// ``` /// /// Because of this property, if you need to hold onto an /// `&lmdb::ConstTransaction` and must explicitly name both lifetimes, /// it is usually best to use the same lifetime for both the reference and the /// parameter, eg `&'x lmdb::ConstTransaction<'x>`. #[derive(Debug)] pub struct ConstTransaction<'env> { env: &'env Environment, tx: TxHandle, has_yielded_accessor: Cell<bool>, } /// A read-only LMDB transaction. /// /// In addition to all operations valid on `ConstTransaction`, a /// `ReadTransaction` can additionally operate on cursors with a lifetime /// scoped to the environment instead of the transaction. /// /// ## Lifetime /// /// All notes for `ConstTransaction` apply. #[derive(Debug)] pub struct ReadTransaction<'env>(ConstTransaction<'env>); /// A read-write LMDB transaction. /// /// In addition to all operations valid on `ConstTransaction`, it is also /// possible to perform writes to the underlying databases. /// /// ## Lifetime /// /// All notes for `ConstTransaction` apply. #[derive(Debug)] pub struct WriteTransaction<'env>(ConstTransaction<'env>); /// A read-only LMDB transaction that has been reset. /// /// It can be renewed by calling `ResetTransaction::renew()`. /// /// ## Lifetime /// /// All notes for `ReadTransaction` apply. #[derive(Debug)] pub struct ResetTransaction<'env>(ReadTransaction<'env>); /// A read-only data accessor obtained from a `ConstTransaction`. /// /// There is no corresponding `ReadAccessor`, since there are no additional /// operations one can do with a known-read-only accessor. /// /// ## Lifetime /// /// A `ConstAccessor` must be outlived by its parent transaction (not /// necessarily strictly). The parent transaction cannot be destroyed /// (committed, etc) until the borrow from the accessor ends. This in many /// cases requires adding an extra scope (with bare `{ }` braces) in which to /// obtain the accessor, as can be seen in many of the examples. /// /// The lifitem of a reference to a `ConstAccessor` dictates the lifetime of /// the data accessed via the accessor. /// /// The `'txn` lifetime parameter is covariant. That is, given two lifetimes /// `'x` and `'y` where `'x: 'y`, a `&ConstAccessor<'x>` can be implicitly /// coerced into a `&ConstAccessor<'y>`. /// /// ```rust,norun /// # #![allow(dead_code)] /// # extern crate lmdb_zero as lmdb; /// # fn main() { } /// # /// fn convariance<'x, 'y>(db: &lmdb::ConstAccessor<'x>) /// where 'x: 'y { /// let _db2: &lmdb::ConstAccessor<'y> = db; /// } /// ``` /// /// Because of this property, if you need to hold onto an /// `&lmdb::ConstAccessor` and must explicitly name both lifetimes, it /// is usually best to use the same lifetime for both the reference and the /// parameter, eg `&'x lmdb::ConstAccessor<'x>`. #[derive(Debug)] pub struct ConstAccessor<'txn>(&'txn ConstTransaction<'txn>); /// A read-write data accessor obtained from a `WriteTransaction`. /// /// All operations that can be performed on `ConstAccessor` can also be /// performed on `WriteAccessor`. /// /// ## Lifetime /// /// Nominally, `WriteAccessor` would behave the same as `ConstAccessor`. /// /// However, there is never any useful reason to explicitly reference a /// `&WriteAccessor` (ie, a shared reference). Instead, one talks about a /// `&mut WriteAccessor`. The unfortunate consequence here is that the `'txn` /// lifetime ends up being _invariant_; that is, the following code will not /// compile: /// /// ```rust,ignore /// # #![allow(dead_code)] /// # extern crate lmdb_zero as lmdb; /// # fn main() { } /// # /// fn convariance<'x, 'y>(db: &mut lmdb::WriteAccessor<'x>) /// where 'x: 'y { /// let _db2: &mut lmdb::WriteAccessor<'y> = db; // ERROR! /// } /// ``` /// /// The compiler's error messages here tend to be unhelpful. In certain cases, /// it will suggest changing the function declaration above to something like /// `&'x mut lmdb::WriteAccessor<'x>`. Applying such a fix when it is suggested /// _will appear to work_. But what happens is that you end up propagating /// `&'txn mut lmdb::WriteAccessor<'txn>` the whole way up your call stack. /// Since `'txn` is invariant, it is inferred to be exactly equal to the /// lifetime of the transaction, and now you've declared that the borrow from /// the transaction exists for the entire lifetime of the transaction. This /// means that you cannot actually commit the transaction. /// /// Instead, make sure you always have separate type parameters on the `&mut` /// and the `WriteAccessor` itself. This can usually be accomplished by letting /// lifetime elision run its course. If you must name both, generally go with /// `&'access mut WriteAccessor<'txn>`. The `'access` lifetime is the lifetime /// of any data you obtain via the accessor. #[derive(Debug)] pub struct WriteAccessor<'txn>(ConstAccessor<'txn>); impl<'env> ConstTransaction<'env> { fn new<'outer: 'env>(env: &'env Environment, parent: Option<&'env mut ConstTransaction<'outer>>, flags: c_uint) -> Result<Self> { let mut rawtx: *mut ffi::MDB_txn = ptr::null_mut(); unsafe { lmdb_call!(ffi::mdb_txn_begin( env::env_ptr(env), parent.map_or(ptr::null_mut(), |p| p.tx.0), flags, &mut rawtx)); } Ok(ConstTransaction { env: env, tx: TxHandle(rawtx), has_yielded_accessor: Cell::new(false), }) } /// Returns an accessor used to manipulate data in this transaction. /// /// ## Panics /// /// Panics if this function has already been called on this transaction. /// /// ## Example /// /// ```rust,should_panic /// # include!("src/example_helpers.rs"); /// # #[allow(unused_vars)] /// # fn main() { /// # let env = create_env(); /// let txn = lmdb::ReadTransaction::new(&env).unwrap(); /// // Get access the first time /// let access = txn.access(); /// /// // You can't get the accessor again, since this would create two /// // references to the same logical memory and allow creating aliased /// // mutable references and so forth. /// let access2 = txn.access(); // PANIC! /// # } /// ``` #[inline] pub fn access(&self) -> ConstAccessor { assert!(!self.has_yielded_accessor.get(), "Transaction accessor already returned"); self.has_yielded_accessor.set(true); ConstAccessor(self) } /// Creates a new cursor scoped to this transaction, bound to the given /// database. #[inline] pub fn cursor<'txn, 'db>(&'txn self, db: &'db Database) -> Result<Cursor<'txn,'db>> { try!(db.assert_same_env(self.env)); let mut raw: *mut ffi::MDB_cursor = ptr::null_mut(); unsafe { lmdb_call!(ffi::mdb_cursor_open(self.tx.0, db.dbi(), &mut raw)); } Ok(unsafe { cursor::create_cursor(raw, self) }) } /// Returns the internal id of this transaction. pub fn id(&self) -> usize { unsafe { ffi2::mdb_txn_id(self.tx.0) } } /// Retrieves statistics for a database. pub fn db_stat(&self, db: &Database) -> Result<Stat> { try!(db.assert_same_env(self.env)); unsafe { let mut raw: ffi::MDB_stat = mem::zeroed(); lmdb_call!(ffi::mdb_stat(self.tx.0, db.dbi(), &mut raw)); Ok(raw.into()) } } /// Retrieve the DB flags for a database handle. pub fn db_flags(&self, db: &Database) -> Result<db::Flags> { try!(db.assert_same_env(self.env)); let mut raw: c_uint = 0; unsafe { lmdb_call!(ffi::mdb_dbi_flags(self.tx.0, db.dbi(), &mut raw)); } Ok(db::Flags::from_bits_truncate(raw)) } #[inline] fn assert_sensible_cursor<'a>(&self, cursor: &Cursor<'env,'a>) -> Result<()> { if self as *const ConstTransaction<'env> != cursor::txn_ref(cursor) as *const ConstTransaction<'env> { Err(Error::Mismatch) } else { Ok(()) } } } // Internally used by other parts of the crate #[inline] pub fn assert_sensible_cursor(access: &ConstAccessor, cursor: &Cursor) -> Result<()> { access.0.assert_sensible_cursor(cursor) } impl<'env> Deref for ReadTransaction<'env> { type Target = ConstTransaction<'env>; fn deref(&self) -> &ConstTransaction<'env> { &self.0 } } impl<'env> DerefMut for ReadTransaction<'env> { fn deref_mut(&mut self) -> &mut ConstTransaction<'env> { &mut self.0 } } impl<'env> ReadTransaction<'env> { /// Opens a new, read-only transaction within the given environment. /// /// ## Note /// /// A transaction and its cursors must only be used by a single thread /// (enforced by the rust compiler), and a thread may only have a single /// transaction at a time. If `NOTLS` is in use, this does not apply to /// read-only transactions. Attempting to open a read-only transaction /// while the current thread holds a read-write transaction will deadlock. pub fn new(env: &'env Environment) -> Result<Self> { Ok(ReadTransaction(try!(ConstTransaction::new( env, None, ffi::MDB_RDONLY)))) } /// Dissociates the given cursor from this transaction and its database, /// returning a `StaleCursor` which can be reused later. /// /// This only fails if `cursor` does not belong to this transaction. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// # let db = lmdb::Database::open( /// # &env, None, &lmdb::DatabaseOptions::defaults()) /// # .unwrap(); /// let mut saved_cursor; /// { /// let txn = lmdb::ReadTransaction::new(&env).unwrap(); /// let cursor = txn.cursor(&db).unwrap(); /// // Do some stuff with `txn` and `cursor` /// /// // We don't want to realloc `cursor` next time, so save it away /// saved_cursor = txn.dissoc_cursor(cursor).unwrap(); /// } // Read transaction goes away, but our saved cursor remains /// /// { /// let txn = lmdb::ReadTransaction::new(&env).unwrap(); /// // Rebind the old cursor. It continues operating on `db`. /// let cursor = txn.assoc_cursor(saved_cursor).unwrap(); /// // Do stuff with txn, cursor /// /// // We can save the cursor away again /// saved_cursor = txn.dissoc_cursor(cursor).unwrap(); /// } /// # } /// ``` pub fn dissoc_cursor<'txn,'db>(&self, cursor: Cursor<'txn,'db>) -> Result<StaleCursor<'db>> where 'env: 'db { try!(self.assert_sensible_cursor(&cursor)); Ok(cursor::to_stale(cursor, self.env)) } /// Associates a saved read-only with this transaction. /// /// The cursor will be rebound to this transaction, but will continue using /// the same database that it was previously. pub fn assoc_cursor<'txn,'db>(&'txn self, cursor: StaleCursor<'db>) -> Result<Cursor<'txn,'db>> { if self.env as *const Environment != cursor::env_ref(&cursor) as *const Environment { return Err(Error::Mismatch) } unsafe { lmdb_call!(ffi::mdb_cursor_renew( self.tx.0, cursor::stale_cursor_ptr(&cursor))); } Ok(cursor::from_stale(cursor, self)) } /// Resets this transaction, releasing most of its resources but allowing /// it to be quickly renewed if desired. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let mut saved_txn; /// { /// let txn = lmdb::ReadTransaction::new(&env).unwrap(); /// { /// let access = txn.access(); /// // Do stuff with `txn`, `access` /// } /// // Save our transaction so we don't have to reallocate it next time, /// // but we also don't keep locks around and will later move to the /// // latest version of the environment. /// saved_txn = txn.reset(); /// } /// /// { /// // Instead of creating a brand new transaction, renew the one we /// // saved. /// let txn = saved_txn.renew().unwrap(); /// { /// let access = txn.access(); /// // Do stuff with `txn`, `access` /// } /// /// // We can save the transaction away again /// saved_txn = txn.reset(); /// } /// # } /// ``` pub fn reset(self) -> ResetTransaction<'env> { unsafe { ffi::mdb_txn_reset(self.0.tx.0); } ResetTransaction(self) } } impl<'env> ResetTransaction<'env> { /// Renews this read-only transaction, making it available for more /// reading. pub fn renew(self) -> Result<ReadTransaction<'env>> { unsafe { lmdb_call!(ffi::mdb_txn_renew((self.0).0.tx.0)); } self.0.has_yielded_accessor.set(false); Ok(self.0) } } impl<'env> Deref for WriteTransaction<'env> { type Target = ConstTransaction<'env>; fn deref(&self) -> &ConstTransaction<'env> { &self.0 } } impl<'env> DerefMut for WriteTransaction<'env> { fn deref_mut(&mut self) -> &mut ConstTransaction<'env> { &mut self.0 } } impl<'env> WriteTransaction<'env> { /// Creates a new, read-write transaction in the given environment. /// /// ## Note /// /// A transaction and its cursors must only be used by a single thread /// (enforced by the rust compiler), and a thread may only have a single /// read-write transaction at a time (even if `NOTLS` is in use --- trying /// to start two top-level read-write transactions on the same thread will /// deadlock). pub fn new(env: &'env Environment) -> Result<Self> { Ok(WriteTransaction(try!(ConstTransaction::new(env, None, 0)))) } /// Opens a new, read-write transaction as a child transaction of the given /// parent. While the new transaction exists, no operations may be /// performed on the parent or any of its cursors. (These bindings are /// actually stricter, and do not permit cursors or other references into /// the parent to coexist with the child transaction.) /// /// After this call, whether or not it succeeds, it is possible to call /// `access()` on the original transaction again one more time, since the /// Rust borrow rules guarantee the old accessor was destroyed by the /// caller already. /// /// ## Note /// /// A transaction and its cursors must only be used by a single thread /// (enforced by the rust compiler). /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, None, &lmdb::DatabaseOptions::defaults()).unwrap(); /// let mut txn = lmdb::WriteTransaction::new(&env).unwrap(); /// let f = lmdb::put::Flags::empty(); /// { /// let mut access = txn.access(); /// access.put(&db, "Germany", "Berlin", f).unwrap(); /// access.put(&db, "Latvia", "Rīga", f).unwrap(); /// access.put(&db, "France", "Paris", f).unwrap(); /// } /// /// { /// // Open a child transaction and do some more reading and writing. /// let subtx = txn.child_tx().unwrap(); /// let mut access = subtx.access(); /// assert_eq!("Berlin", access.get::<str,str>(&db, "Germany").unwrap()); /// access.put(&db, "Germany", "Frankfurt", f).unwrap(); /// assert_eq!("Frankfurt", access.get::<str,str>(&db, "Germany").unwrap()); /// // Don't commit --- let the child transaction abort (roll back) /// } /// /// { /// let mut access = txn.access(); /// // Now we can do some more reading and writing on the original /// // transaction. /// // The effect of the aborted child transaction are not visible. /// access.put(&db, "United Kingdom", "London", f).unwrap(); /// assert_eq!("Berlin", access.get::<str,str>(&db, "Germany").unwrap()); /// } /// /// { /// // Another child. /// let subtx = txn.child_tx().unwrap(); /// { /// let mut access = subtx.access(); /// access.put(&db, "Spain", "Madrid", f).unwrap(); /// } /// // Commit this one this time. /// subtx.commit().unwrap(); /// } /// /// { /// // Now the changes from the child are visible to this transaction, /// // but still not outside it. /// let mut access = txn.access(); /// assert_eq!("Madrid", access.get::<str,str>(&db, "Spain").unwrap()); /// } /// /// txn.commit().unwrap(); /// # } /// ``` pub fn child_tx<'a>(&'a mut self) -> Result<WriteTransaction<'a>> where 'env: 'a { // Allow the caller to later retrieve a new accessor, since the borrow // rules ensure that they've destroyed the old one. self.has_yielded_accessor.set(false); let env = self.0.env; Ok(WriteTransaction(try!(ConstTransaction::new( env, Some(&mut*self), 0)))) } /// Commits this write transaction. pub fn commit(mut self) -> Result<()> { unsafe { self.0.tx.commit() } } /// Returns a read/write accessor on this transaction. /// /// ## Panics /// /// Panics if called more than once on the same transaction. #[inline] pub fn access(&self) -> WriteAccessor { WriteAccessor(self.0.access()) } } impl<'txn> ConstAccessor<'txn> { /// Get items from a database. /// /// This function retrieves key/data pairs from the database. A reference /// to the data associated with the given key is returned. If the database /// supports duplicate keys (`DUPSORT`) then the first data item for the /// key will be returned. Retrieval of other items requires the use of /// cursoring. /// /// The returned memory is valid until the next mutation through the /// transaction or the end of the transaction (both are enforced through /// the borrow checker). /// /// ## Errors /// /// This call may return errors for reasons other than the key not being /// found. The easiest way to handle "not found" is generally to use the /// `to_opt` method on `traits::LmdbResultExt` to promote the value into a /// `Result<Option<V>>`. Most important of these other errors is the /// possibility of the key being found, but the value not being convertible /// to a `&V`. #[inline] pub fn get<K : AsLmdbBytes + ?Sized, V : FromLmdbBytes + ?Sized>( &self, db: &Database, key: &K) -> Result<&V> { try!(db.assert_same_env(self.env())); let mut mv_key = as_val(key); let mut out_val = EMPTY_VAL; unsafe { lmdb_call!(ffi::mdb_get( self.txptr(), db.dbi(), &mut mv_key, &mut out_val)); } from_val(self, &out_val) } fn txptr(&self) -> *mut ffi::MDB_txn { self.0.tx.0 } fn env(&self) -> &Environment { self.0.env } } impl<'txn> Deref for WriteAccessor<'txn> { type Target = ConstAccessor<'txn>; fn deref(&self) -> &ConstAccessor<'txn> { &self.0 } } impl<'txn> WriteAccessor<'txn> { /// Store items into a database. /// /// This function stores key/data pairs in the database. The default /// behavior is to enter the new key/data pair, replacing any previously /// existing key if duplicates are disallowed, or adding a duplicate data /// item if duplicates are allowed (`DUPSORT`). #[inline] pub fn put<K : AsLmdbBytes + ?Sized, V : AsLmdbBytes + ?Sized>( &mut self, db: &Database, key: &K, value: &V, flags: put::Flags) -> Result<()> { try!(db.assert_same_env(self.env())); let mut mv_key = as_val(key); let mut mv_val = as_val(value); unsafe { lmdb_call!(ffi::mdb_put( self.txptr(), db.dbi(), &mut mv_key, &mut mv_val, flags.bits())); } Ok(()) } /// Store items into a database. /// /// This function stores key/data pairs in the database. The default /// behavior is to enter the new key/data pair, replacing any previously /// existing key if duplicates are disallowed, or adding a duplicate data /// item if duplicates are allowed (`DUPSORT`). /// /// Unlike `put()`, this does not take a value. Instead, it reserves space /// for the value (equal to the size of `V`) and then returns a mutable /// reference to it. Be aware that the `FromReservedLmdbBytes` conversion /// will be invoked on whatever memory happens to be at the destination /// location. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// #[repr(C, packed)] /// #[derive(Clone,Copy,Debug,PartialEq,Eq)] /// struct MyStruct { /// x: i32, /// y: i32, /// } /// unsafe impl lmdb::traits::LmdbRaw for MyStruct { } /// /// # fn main() { /// # let env = create_env(); /// # let db = lmdb::Database::open( /// # &env, None, &lmdb::DatabaseOptions::defaults()) /// # .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// { /// let dst: &mut MyStruct = access.put_reserve( /// &db, "foo", lmdb::put::Flags::empty()).unwrap(); /// // Writing to `dst` actually writes directly into the database. /// dst.x = 42; /// dst.y = 56; /// // Drop `dst` so we can use `access` again /// } /// assert_eq!(&MyStruct { x: 42, y: 56 }, /// access.get(&db, "foo").unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` #[inline] pub fn put_reserve<K : AsLmdbBytes + ?Sized, V : FromReservedLmdbBytes + Sized>( &mut self, db: &Database, key: &K, flags: put::Flags) -> Result<&mut V> { unsafe { self.put_reserve_unsized(db, key, mem::size_of::<V>(), flags) } } /// Store items into a database. /// /// This function stores key/data pairs in the database. The default /// behavior is to enter the new key/data pair, replacing any previously /// existing key if duplicates are disallowed, or adding a duplicate data /// item if duplicates are allowed (`DUPSORT`). /// /// Unlike `put()`, this does not take a value. Instead, it reserves space /// for the value (equal to an array of `count` objects of size `V`) and /// then returns a mutable reference to it. Be aware that the content of /// the returned slice is simply whatever happens to be in the destination /// memory at the time of this call. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// # let db = lmdb::Database::open( /// # &env, None, &lmdb::DatabaseOptions::defaults()) /// # .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// { /// let bytes: &mut [u8] = access.put_reserve_array( /// &db, "foo", 4, lmdb::put::Flags::empty()).unwrap(); /// // More realistically, one could zero-copy data from a file/socket /// // into `bytes`, for example. /// bytes[0] = b'b'; bytes[1] = b'y'; /// bytes[2] = b't'; bytes[3] = b'e'; /// } /// assert_eq!("byte", access.get::<str,str>(&db, "foo").unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` #[inline] pub fn put_reserve_array<K : AsLmdbBytes + ?Sized, V : LmdbRaw>( &mut self, db: &Database, key: &K, count: usize, flags: put::Flags) -> Result<&mut [V]> { unsafe { self.put_reserve_unsized( db, key, mem::size_of::<V>() * count, flags) } } /// Store items into a database. /// /// This function stores key/data pairs in the database. The default /// behavior is to enter the new key/data pair, replacing any previously /// existing key if duplicates are disallowed, or adding a duplicate data /// item if duplicates are allowed (`DUPSORT`). /// /// Unlike `put()`, this does not take a value. Instead, it reserves space /// equal to `size` bytes for the value and then returns a mutable /// reference to it. Be aware that the `FromReservedLmdbBytes` conversion /// will be invoked on whatever memory happens to be at the destination /// location. /// /// ## Unsafety /// /// The caller must ensure that `size` is a valid size for `V`. #[inline] pub unsafe fn put_reserve_unsized<K : AsLmdbBytes + ?Sized, V : FromReservedLmdbBytes + ?Sized>( &mut self, db: &Database, key: &K, size: usize, flags: put::Flags) -> Result<&mut V> { try!(db.assert_same_env(self.env())); let mut mv_key = as_val(key); let mut out_val = EMPTY_VAL; out_val.mv_size = size; lmdb_call!(ffi::mdb_put( self.txptr(), db.dbi(), &mut mv_key, &mut out_val, flags.bits() | ffi::MDB_RESERVE)); Ok(from_reserved(self, &out_val)) } /// Delete items from a database by key. /// /// This function removes key/data pairs from the database. All values /// whose key matches `key` are deleted, including in the case of /// `DUPSORT`. This function will return `NOTFOUND` if the specified /// key is not in the database. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("example"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// assert_eq!("Apple", access.get::<str,str>(&db, "Fruit").unwrap()); /// access.del_key(&db, "Fruit").unwrap(); /// assert!(access.get::<str,str>(&db, "Fruit").is_err()); /// } /// txn.commit().unwrap(); /// # } /// ``` #[inline] pub fn del_key<K : AsLmdbBytes + ?Sized>( &mut self, db: &Database, key: &K) -> Result<()> { try!(db.assert_same_env(self.env())); let mut mv_key = as_val(key); unsafe { lmdb_call!(ffi::mdb_del( self.txptr(), db.dbi(), &mut mv_key, ptr::null_mut())); } Ok(()) } /// Delete items from a database by key and value. /// /// This function removes key/data pairs from the database. If the database /// does not support sorted duplicate data items (`DUPSORT`) the `val` /// parameter is ignored and this call behaves like `del()`. Otherwise, if /// the data item matching both `key` and `val` will be deleted. This /// function will return `NOTFOUND` if the specified key/data pair is not /// in the database. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// let db = lmdb::Database::open( /// &env, Some("example"), /// &lmdb::DatabaseOptions::create_multimap_unsized::<str,str>()) /// .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// access.put(&db, "Fruit", "Apple", lmdb::put::Flags::empty()).unwrap(); /// access.put(&db, "Fruit", "Orange", lmdb::put::Flags::empty()).unwrap(); /// assert_eq!("Apple", access.get::<str,str>(&db, "Fruit").unwrap()); /// access.del_item(&db, "Fruit", "Apple").unwrap(); /// assert_eq!("Orange", access.get::<str,str>(&db, "Fruit").unwrap()); /// } /// txn.commit().unwrap(); /// # } /// ``` #[inline] pub fn del_item<K : AsLmdbBytes + ?Sized, V : AsLmdbBytes + ?Sized>( &mut self, db: &Database, key: &K, val: &V) -> Result<()> { try!(db.assert_same_env(self.env())); let mut mv_key = as_val(key); let mut mv_val = as_val(val); unsafe { lmdb_call!(ffi::mdb_del( self.txptr(), db.dbi(), &mut mv_key, &mut mv_val)); } Ok(()) } /// Completely clears the content of the given database. /// /// ## Example /// /// ``` /// # include!("src/example_helpers.rs"); /// # fn main() { /// # let env = create_env(); /// # let db = lmdb::Database::open( /// # &env, None, &lmdb::DatabaseOptions::defaults()) /// # .unwrap(); /// let txn = lmdb::WriteTransaction::new(&env).unwrap(); /// { /// let mut access = txn.access(); /// let f = lmdb::put::Flags::empty(); /// access.put(&db, "Germany", "Berlin", f).unwrap(); /// access.put(&db, "France", "Paris", f).unwrap(); /// access.put(&db, "Latvia", "Rīga", f).unwrap(); /// assert_eq!(3, txn.db_stat(&db).unwrap().entries); /// /// access.clear_db(&db).unwrap(); /// assert_eq!(0, txn.db_stat(&db).unwrap().entries); /// } /// txn.commit().unwrap(); /// # } /// ``` pub fn clear_db(&mut self, db: &Database) -> Result<()> { try!(db.assert_same_env(self.env())); unsafe { lmdb_call!(ffi::mdb_drop(self.txptr(), db.dbi(), 0)); } Ok(()) } }