Crate rt_map

Expand description

Runtime managed mutable borrowing from a map.

This library provides a map that allows mutable borrows to different entries at the same time. For a map implementation of this, see rt_vec.

The implementation is extracted and slightly modified from shred.

Usage

Add the following to Cargo.toml

rt_map = "0.5.2" # or
rt_map = { version = "0.5.2", features = ["unsafe_debug"] }

In code:

use rt_map::RtMap;

struct A(u32);

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_ok() {
    "Ok(..)"
} else {
    "Err"
};
println!("a_try_borrow_mut: {}", exists); // prints "Err"