Mercurial > lbo > hg > leveldb-rs
view src/types.rs @ 221:d7de5c816802
all: Smaller clean-ups.
author | Lewin Bormann <lbo@spheniscida.de> |
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date | Sat, 09 Sep 2017 17:21:32 +0200 |
parents | 6e1e7c828b69 |
children | 188a52d70d4e |
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//! A collection of fundamental and/or simple types used by other modules use std::cell::RefCell; use std::rc::Rc; #[derive(Debug, PartialOrd, PartialEq)] pub enum ValueType { TypeDeletion = 0, TypeValue = 1, } /// Represents a sequence number of a single entry. pub type SequenceNumber = u64; pub const MAX_SEQUENCE_NUMBER: SequenceNumber = (1 << 56) - 1; /// A shared thingy with interior mutability. pub type Shared<T> = Rc<RefCell<T>>; pub fn share<T>(t: T) -> Rc<RefCell<T>> { Rc::new(RefCell::new(t)) } /// Denotes a key range pub struct Range<'a> { pub start: &'a [u8], pub limit: &'a [u8], } /// An extension of the standard `Iterator` trait that supports some methods necessary for LevelDB. /// This works because the iterators used are stateful and keep the last returned element. /// /// Note: Implementing types are expected to hold `!valid()` before the first call to `advance()`. /// /// test_util::test_iterator_properties() verifies that all properties hold. pub trait LdbIterator { /// advance advances the position of the iterator by one element (which can be retrieved using /// current(). If no more elements are available, advance() returns false, and the iterator /// becomes invalid (i.e. like reset() has been called). fn advance(&mut self) -> bool; /// Return the current item (i.e. the item most recently returned by get_next()) fn current(&self, key: &mut Vec<u8>, val: &mut Vec<u8>) -> bool; /// Seek the iterator to `key` or the next bigger key. If the seek is invalid (past last /// element), the iterator is reset() and not valid. /// After a seek to an existing key, current() returns that entry. fn seek(&mut self, key: &[u8]); /// Resets the iterator to be `!valid()` again (before first element) fn reset(&mut self); /// Returns true if the iterator is not positioned before the first or after the last element, /// i.e. if current() would return an entry. fn valid(&self) -> bool; /// Go to the previous item; if the iterator has reached the "before-first" item, prev() /// returns false, and the iterator is invalid. This is inefficient for most iterators. fn prev(&mut self) -> bool; // default implementations. /// next is like Iterator::next(). It's implemented here because "only traits defined in the /// current crate can be implemented for a type parameter" (says rustc). fn next(&mut self) -> Option<(Vec<u8>, Vec<u8>)> { if !self.advance() { return None; } let (mut key, mut val) = (vec![], vec![]); if self.current(&mut key, &mut val) { Some((key, val)) } else { None } } /// seek_to_first seeks to the first element. fn seek_to_first(&mut self) { self.reset(); self.advance(); } } /// current_key_val is a helper allocating two vectors and filling them with the current key/value /// of the specified iterator. pub fn current_key_val<It: LdbIterator + ?Sized>(it: &It) -> Option<(Vec<u8>, Vec<u8>)> { let (mut k, mut v) = (vec![], vec![]); if it.current(&mut k, &mut v) { Some((k, v)) } else { None } } /// The unique (sequential) number of a file. pub type FileNum = u64; /// Describes a file on disk. #[derive(Clone, Debug, PartialEq)] pub struct FileMetaData { // default: size / 16384. pub allowed_seeks: isize, pub num: FileNum, pub size: usize, // these are in InternalKey format: pub smallest: Vec<u8>, pub largest: Vec<u8>, } pub const NUM_LEVELS: usize = 7;