Mercurial > lbo > hg > memoize
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Added tag v0.4.1 for changeset 793f2e38a318
author | Lewin Bormann <lbo@spheniscida.de> |
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date | Fri, 27 Oct 2023 20:22:19 +0200 |
parents | 7d8d8525f957 |
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# memoize [![Docs.rs](https://docs.rs/memoize/badge.svg)](https://docs.rs/memoize) [![Crates.rs](https://img.shields.io/crates/v/memoize.svg)](https://crates.io/crates/memoize) [![CI](https://github.com/dermesser/rex/workflows/CI/badge.svg)](https://github.com/dermesser/memoize/actions?query=workflow%3ACI) A `#[memoize]` attribute for somewhat simple Rust functions: That is, functions with one or more `Clone`-able arguments, and a `Clone`-able return type. That's it. **NEWS**: The crate has been updated so that you don't need to separately import `lru`, `lazy_static`, and other dependencies. Now everything should work automatically. Remember to enable the `full` feature to use LRU caching and other additional features. Read the documentation (`cargo doc --open`) for the sparse details, or take a look at the `examples/`, if you want to know more: ```rust // From examples/test2.rs use memoize::memoize; #[memoize] fn hello(arg: String, arg2: usize) -> bool { arg.len()%2 == arg2 } fn main() { // `hello` is only called once here. assert!(! hello("World".to_string(), 0)); assert!(! hello("World".to_string(), 0)); // Sometimes one might need the original function. assert!(! memoized_original_hello("World".to_string(), 0)); } ``` This is expanded into (with a few simplifications): ```rust std::thread_local! { static MEMOIZED_MAPPING_HELLO : RefCell<HashMap<(String, usize), bool>> = RefCell::new(HashMap::new()); } pub fn memoized_original_hello(arg: String, arg2: usize) -> bool { arg.len() % 2 == arg2 } #[allow(unused_variables)] fn hello(arg: String, arg2: usize) -> bool { let ATTR_MEMOIZE_RETURN__ = MEMOIZED_MAPPING_HELLO.with(|ATTR_MEMOIZE_HM__| { let mut ATTR_MEMOIZE_HM__ = ATTR_MEMOIZE_HM__.borrow_mut(); ATTR_MEMOIZE_HM__.get(&(arg.clone(), arg2.clone())).cloned() }); if let Some(ATTR_MEMOIZE_RETURN__) = ATTR_MEMOIZE_RETURN__ { return ATTR_MEMOIZE_RETURN__; } let ATTR_MEMOIZE_RETURN__ = memoized_original_hello(arg.clone(), arg2.clone()); MEMOIZED_MAPPING_HELLO.with(|ATTR_MEMOIZE_HM__| { let mut ATTR_MEMOIZE_HM__ = ATTR_MEMOIZE_HM__.borrow_mut(); ATTR_MEMOIZE_HM__.insert((arg, arg2), ATTR_MEMOIZE_RETURN__.clone()); }); r } ``` ## Further Functionality As can be seen in the above example, each thread has its own cache by default. If you would prefer that every thread share the same cache, you can specify the `SharedCache` option like below to wrap the cache in a `std::sync::Mutex`. For example: ```rust #[memoize(SharedCache)] fn hello(key: String) -> ComplexStruct { // ... } ``` You can choose to use an [LRU cache](https://crates.io/crates/lru). In fact, if you know that a memoized function has an unbounded number of different inputs, you should do this! In that case, use the attribute like this: ```rust // From examples/test1.rs // Compile with --features=full use memoize::memoize; #[derive(Debug, Clone)] struct ComplexStruct { // ... } #[memoize(Capacity: 123)] fn hello(key: String) -> ComplexStruct { // ... } ``` Adding more caches and configuration options is relatively simple, and a matter of parsing attribute parameters. Currently, compiling will fail if you use a parameter such as `Capacity` without the feature `full` being enabled. Another parameter is TimeToLive, specifying how long a cached value is allowed to live: ```rust #[memoize(Capacity: 123, TimeToLive: Duration::from_secs(2))] ``` `chrono::Duration` is also possible, but would have to first be converted to `std::time::Duration` ```rust #[memoize(TimeToLive: chrono::Duration::hours(3).to_std().unwrap())] ``` The cached value will never be older than duration provided and instead recalculated on the next request. You can also specifiy a **custom hasher**, like [AHash](https://github.com/tkaitchuck/aHash) using `CustomHasher`. ```rust #[memoize(CustomHasher: ahash::HashMap)] ``` As some hashers initializing functions other than `new()`, you can specifiy a `HasherInit` function call: ```rust #[memoize(CustomHasher: FxHashMap, HasherInit: FxHashMap::default())] ``` ### Flushing If you memoize a function `f`, there will be a function called `memoized_flush_f()` that allows you to clear the memoization cache. ## Contributions ...are always welcome! This being my first procedural-macros crate, I am grateful for improvements of functionality and style. Please send a pull request, and don't be discouraged if it takes a while for me to review it; I'm sometimes a bit slow to catch up here :) -- Lewin