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// Copyright 2020 Tyler Neely // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. use crate::{ffi, ColumnFamily, Error, ReadOptions, WriteBatch, DB}; use libc::{c_char, c_uchar, size_t}; use std::marker::PhantomData; use std::slice; /// An iterator over a database or column family, with specifiable /// ranges and direction. /// /// This iterator is different to the standard ``DBIterator`` as it aims Into /// replicate the underlying iterator API within RocksDB itself. This should /// give access to more performance and flexibility but departs from the /// widely recognised Rust idioms. /// /// ``` /// use rocksdb::{DB, Options}; /// /// let path = "_path_for_rocksdb_storage4"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.raw_iterator(); /// /// // Forwards iteration /// iter.seek_to_first(); /// while iter.valid() { /// println!("Saw {:?} {:?}", iter.key(), iter.value()); /// iter.next(); /// } /// /// // Reverse iteration /// iter.seek_to_last(); /// while iter.valid() { /// println!("Saw {:?} {:?}", iter.key(), iter.value()); /// iter.prev(); /// } /// /// // Seeking /// iter.seek(b"my key"); /// while iter.valid() { /// println!("Saw {:?} {:?}", iter.key(), iter.value()); /// iter.next(); /// } /// /// // Reverse iteration from key /// // Note, use seek_for_prev when reversing because if this key doesn't exist, /// // this will make the iterator start from the previous key rather than the next. /// iter.seek_for_prev(b"my key"); /// while iter.valid() { /// println!("Saw {:?} {:?}", iter.key(), iter.value()); /// iter.prev(); /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub struct DBRawIterator<'a> { inner: *mut ffi::rocksdb_iterator_t, /// When iterate_upper_bound is set, the inner C iterator keeps a pointer to the upper bound /// inside `_readopts`. Storing this makes sure the upper bound is always alive when the /// iterator is being used. _readopts: ReadOptions, db: PhantomData<&'a DB>, } impl<'a> DBRawIterator<'a> { pub(crate) fn new(db: &DB, readopts: ReadOptions) -> DBRawIterator<'a> { unsafe { DBRawIterator { inner: ffi::rocksdb_create_iterator(db.inner, readopts.inner), _readopts: readopts, db: PhantomData, } } } pub(crate) fn new_cf( db: &DB, cf_handle: &ColumnFamily, readopts: ReadOptions, ) -> DBRawIterator<'a> { unsafe { DBRawIterator { inner: ffi::rocksdb_create_iterator_cf(db.inner, readopts.inner, cf_handle.inner), _readopts: readopts, db: PhantomData, } } } /// Returns `true` if the iterator is valid. An iterator is invalidated when /// it reaches the end of its defined range, or when it encounters an error. /// /// To check whether the iterator encountered an error after `valid` has /// returned `false`, use the [`status`](DBRawIterator::status) method. `status` will never /// return an error when `valid` is `true`. pub fn valid(&self) -> bool { unsafe { ffi::rocksdb_iter_valid(self.inner) != 0 } } /// Returns an error `Result` if the iterator has encountered an error /// during operation. When an error is encountered, the iterator is /// invalidated and [`valid`](DBRawIterator::valid) will return `false` when called. /// /// Performing a seek will discard the current status. pub fn status(&self) -> Result<(), Error> { unsafe { ffi_try!(ffi::rocksdb_iter_get_error(self.inner)); } Ok(()) } /// Seeks to the first key in the database. /// /// # Examples /// /// ```rust /// use rocksdb::{DB, Options}; /// /// let path = "_path_for_rocksdb_storage5"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.raw_iterator(); /// /// // Iterate all keys from the start in lexicographic order /// iter.seek_to_first(); /// /// while iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// iter.next(); /// } /// /// // Read just the first key /// iter.seek_to_first(); /// /// if iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// } else { /// // There are no keys in the database /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub fn seek_to_first(&mut self) { unsafe { ffi::rocksdb_iter_seek_to_first(self.inner); } } /// Seeks to the last key in the database. /// /// # Examples /// /// ```rust /// use rocksdb::{DB, Options}; /// /// let path = "_path_for_rocksdb_storage6"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.raw_iterator(); /// /// // Iterate all keys from the end in reverse lexicographic order /// iter.seek_to_last(); /// /// while iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// iter.prev(); /// } /// /// // Read just the last key /// iter.seek_to_last(); /// /// if iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// } else { /// // There are no keys in the database /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub fn seek_to_last(&mut self) { unsafe { ffi::rocksdb_iter_seek_to_last(self.inner); } } /// Seeks to the specified key or the first key that lexicographically follows it. /// /// This method will attempt to seek to the specified key. If that key does not exist, it will /// find and seek to the key that lexicographically follows it instead. /// /// # Examples /// /// ```rust /// use rocksdb::{DB, Options}; /// /// let path = "_path_for_rocksdb_storage7"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.raw_iterator(); /// /// // Read the first key that starts with 'a' /// iter.seek(b"a"); /// /// if iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// } else { /// // There are no keys in the database /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub fn seek<K: AsRef<[u8]>>(&mut self, key: K) { let key = key.as_ref(); unsafe { ffi::rocksdb_iter_seek( self.inner, key.as_ptr() as *const c_char, key.len() as size_t, ); } } /// Seeks to the specified key, or the first key that lexicographically precedes it. /// /// Like ``.seek()`` this method will attempt to seek to the specified key. /// The difference with ``.seek()`` is that if the specified key do not exist, this method will /// seek to key that lexicographically precedes it instead. /// /// # Examples /// /// ```rust /// use rocksdb::{DB, Options}; /// /// let path = "_path_for_rocksdb_storage8"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.raw_iterator(); /// /// // Read the last key that starts with 'a' /// iter.seek_for_prev(b"b"); /// /// if iter.valid() { /// println!("{:?} {:?}", iter.key(), iter.value()); /// } else { /// // There are no keys in the database /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub fn seek_for_prev<K: AsRef<[u8]>>(&mut self, key: K) { let key = key.as_ref(); unsafe { ffi::rocksdb_iter_seek_for_prev( self.inner, key.as_ptr() as *const c_char, key.len() as size_t, ); } } /// Seeks to the next key. pub fn next(&mut self) { unsafe { ffi::rocksdb_iter_next(self.inner); } } /// Seeks to the previous key. pub fn prev(&mut self) { unsafe { ffi::rocksdb_iter_prev(self.inner); } } /// Returns a slice of the current key. pub fn key(&self) -> Option<&[u8]> { if self.valid() { // Safety Note: This is safe as all methods that may invalidate the buffer returned // take `&mut self`, so borrow checker will prevent use of buffer after seek. unsafe { let mut key_len: size_t = 0; let key_len_ptr: *mut size_t = &mut key_len; let key_ptr = ffi::rocksdb_iter_key(self.inner, key_len_ptr) as *const c_uchar; Some(slice::from_raw_parts(key_ptr, key_len as usize)) } } else { None } } /// Returns a slice of the current value. pub fn value(&self) -> Option<&[u8]> { if self.valid() { // Safety Note: This is safe as all methods that may invalidate the buffer returned // take `&mut self`, so borrow checker will prevent use of buffer after seek. unsafe { let mut val_len: size_t = 0; let val_len_ptr: *mut size_t = &mut val_len; let val_ptr = ffi::rocksdb_iter_value(self.inner, val_len_ptr) as *const c_uchar; Some(slice::from_raw_parts(val_ptr, val_len as usize)) } } else { None } } } impl<'a> Drop for DBRawIterator<'a> { fn drop(&mut self) { unsafe { ffi::rocksdb_iter_destroy(self.inner); } } } unsafe impl<'a> Send for DBRawIterator<'a> {} unsafe impl<'a> Sync for DBRawIterator<'a> {} /// An iterator over a database or column family, with specifiable /// ranges and direction. /// /// ``` /// use rocksdb::{DB, Direction, IteratorMode, Options}; /// /// let path = "_path_for_rocksdb_storage2"; /// { /// let db = DB::open_default(path).unwrap(); /// let mut iter = db.iterator(IteratorMode::Start); // Always iterates forward /// for (key, value) in iter { /// println!("Saw {:?} {:?}", key, value); /// } /// iter = db.iterator(IteratorMode::End); // Always iterates backward /// for (key, value) in iter { /// println!("Saw {:?} {:?}", key, value); /// } /// iter = db.iterator(IteratorMode::From(b"my key", Direction::Forward)); // From a key in Direction::{forward,reverse} /// for (key, value) in iter { /// println!("Saw {:?} {:?}", key, value); /// } /// /// // You can seek with an existing Iterator instance, too /// iter = db.iterator(IteratorMode::Start); /// iter.set_mode(IteratorMode::From(b"another key", Direction::Reverse)); /// for (key, value) in iter { /// println!("Saw {:?} {:?}", key, value); /// } /// } /// let _ = DB::destroy(&Options::default(), path); /// ``` pub struct DBIterator<'a> { raw: DBRawIterator<'a>, direction: Direction, just_seeked: bool, } pub enum Direction { Forward, Reverse, } pub type KVBytes = (Box<[u8]>, Box<[u8]>); pub enum IteratorMode<'a> { Start, End, From(&'a [u8], Direction), } impl<'a> DBIterator<'a> { pub(crate) fn new(db: &DB, readopts: ReadOptions, mode: IteratorMode) -> DBIterator<'a> { let mut rv = DBIterator { raw: DBRawIterator::new(db, readopts), direction: Direction::Forward, // blown away by set_mode() just_seeked: false, }; rv.set_mode(mode); rv } pub(crate) fn new_cf( db: &DB, cf_handle: &ColumnFamily, readopts: ReadOptions, mode: IteratorMode, ) -> DBIterator<'a> { let mut rv = DBIterator { raw: DBRawIterator::new_cf(db, cf_handle, readopts), direction: Direction::Forward, // blown away by set_mode() just_seeked: false, }; rv.set_mode(mode); rv } pub fn set_mode(&mut self, mode: IteratorMode) { match mode { IteratorMode::Start => { self.raw.seek_to_first(); self.direction = Direction::Forward; } IteratorMode::End => { self.raw.seek_to_last(); self.direction = Direction::Reverse; } IteratorMode::From(key, Direction::Forward) => { self.raw.seek(key); self.direction = Direction::Forward; } IteratorMode::From(key, Direction::Reverse) => { self.raw.seek_for_prev(key); self.direction = Direction::Reverse; } }; self.just_seeked = true; } /// See [`valid`](DBRawIterator::valid) pub fn valid(&self) -> bool { self.raw.valid() } /// See [`status`](DBRawIterator::status) pub fn status(&self) -> Result<(), Error> { self.raw.status() } } impl<'a> Iterator for DBIterator<'a> { type Item = KVBytes; fn next(&mut self) -> Option<KVBytes> { if !self.raw.valid() { return None; } // Initial call to next() after seeking should not move the iterator // or the first item will not be returned if self.just_seeked { self.just_seeked = false; } else { match self.direction { Direction::Forward => self.raw.next(), Direction::Reverse => self.raw.prev(), } } if self.raw.valid() { // .key() and .value() only ever return None if valid == false, which we've just cheked Some(( Box::from(self.raw.key().unwrap()), Box::from(self.raw.value().unwrap()), )) } else { None } } } impl<'a> Into<DBRawIterator<'a>> for DBIterator<'a> { fn into(self) -> DBRawIterator<'a> { self.raw } } /// Iterates the batches of writes since a given sequence number. /// /// `DBWALIterator` is returned by `DB::get_updates_since()` and will return the /// batches of write operations that have occurred since a given sequence number /// (see `DB::latest_sequence_number()`). This iterator cannot be constructed by /// the application. /// /// The iterator item type is a tuple of (`u64`, `WriteBatch`) where the first /// value is the sequence number of the associated write batch. /// pub struct DBWALIterator { pub(crate) inner: *mut ffi::rocksdb_wal_iterator_t, } impl DBWALIterator { /// Returns `true` if the iterator is valid. An iterator is invalidated when /// it reaches the end of its defined range, or when it encounters an error. /// /// To check whether the iterator encountered an error after `valid` has /// returned `false`, use the [`status`](DBWALIterator::status) method. /// `status` will never return an error when `valid` is `true`. pub fn valid(&self) -> bool { unsafe { ffi::rocksdb_wal_iter_valid(self.inner) != 0 } } /// Returns an error `Result` if the iterator has encountered an error /// during operation. When an error is encountered, the iterator is /// invalidated and [`valid`](DBWALIterator::valid) will return `false` when /// called. pub fn status(&self) -> Result<(), Error> { unsafe { ffi_try!(ffi::rocksdb_wal_iter_status(self.inner)); } Ok(()) } } impl Iterator for DBWALIterator { type Item = (u64, WriteBatch); fn next(&mut self) -> Option<(u64, WriteBatch)> { // Seek to the next write batch. unsafe { ffi::rocksdb_wal_iter_next(self.inner); } if self.valid() { let mut seq: u64 = 0; let inner = unsafe { ffi::rocksdb_wal_iter_get_batch(self.inner, &mut seq) }; Some((seq, WriteBatch { inner })) } else { None } } } impl Drop for DBWALIterator { fn drop(&mut self) { unsafe { ffi::rocksdb_wal_iter_destroy(self.inner); } } }