🗃️ rt_map

Runtime managed mutable borrowing from a map.

This library provides a map that allows mutable borrows to different entries at the same time.

This implementation is extracted and slightly modified from shred.

Usage

Add the following to Cargo.toml

rt_map = "0.4.0"

In code:

use rt_map::RtMap;

struct A(u32);

fn main() {
    let mut rt_map = RtMap::new();

    rt_map.insert('a', A(1));
    rt_map.insert('b', A(2));

    // We can validly have two mutable borrows from the `RtMap` map!
    let mut a = rt_map.borrow_mut(&'a');
    let mut b = rt_map.borrow_mut(&'b');
    a.0 = 2;
    b.0 = 3;

    // We need to explicitly drop the A and B borrows, because they are runtime
    // managed borrows, and rustc doesn't know to drop them before the immutable
    // borrows after this.
    drop(a);
    drop(b);

    // Multiple immutable borrows to the same value are valid.
    let a_0 = rt_map.borrow(&'a');
    let _a_1 = rt_map.borrow(&'a');
    let b = rt_map.borrow(&'b');

    println!("A: {}", a_0.0);
    println!("B: {}", b.0);

    // Trying to mutably borrow a value that is already borrowed (immutably
    // or mutably) returns `Err`.
    let a_try_borrow_mut = rt_map.try_borrow_mut(&'a');
    let exists = if a_try_borrow_mut.is_some() {
        "Ok(..)"
    } else {
        "Err"
    };
    println!("a_try_borrow_mut: {}", exists); // prints "Err"
}

See Also

• anymap: Map of any type, without multiple mutable borrows.
• resman: Map of any type, with runtime managed borrowing.
• shred: Like resman, plus a task dispatcher.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.