Crate matchit 

A high performance, zero-copy URL router.

use matchit::Router;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut router = Router::new();
    router.insert("/home", "Welcome!")?;
    router.insert("/users/{id}", "A User")?;

    let matched = router.at("/users/978")?;
    assert_eq!(matched.params.get("id"), Some("978"));
    assert_eq!(*matched.value, "A User");

    Ok(())
}

Parameters

The router supports dynamic route segments. These can either be named or catch-all parameters.

Named parameters like /{id} match anything until the next static segment or the end of the path.

let mut router = Router::new();
router.insert("/users/{id}", 42)?;

let matched = router.at("/users/1")?;
assert_eq!(matched.params.get("id"), Some("1"));

let matched = router.at("/users/23")?;
assert_eq!(matched.params.get("id"), Some("23"));

assert!(router.at("/users").is_err());

Prefixes and suffixes within a segment are also supported. However, there may only be a single named parameter per route segment.

let mut router = Router::new();
router.insert("/images/img-{id}.png", true)?;

let matched = router.at("/images/img-1.png")?;
assert_eq!(matched.params.get("id"), Some("1"));

assert!(router.at("/images/img-1.jpg").is_err());

Catch-all parameters start with a * and match anything until the end of the path. They must always be at the end of the route.

let mut router = Router::new();
router.insert("/{*rest}", true)?;

let matched = router.at("/foo.html")?;
assert_eq!(matched.params.get("rest"), Some("foo.html"));

let matched = router.at("/static/bar.css")?;
assert_eq!(matched.params.get("rest"), Some("static/bar.css"));

// Note that this would lead to an empty parameter value.
assert!(router.at("/").is_err());

The literal characters { and } may be included in a static route by escaping them with the same character. For example, the { character is escaped with {{, and the } character is escaped with }}.

let mut router = Router::new();
router.insert("/{{hello}}", true)?;
router.insert("/{hello}", true)?;

// Match the static route.
let matched = router.at("/{hello}")?;
assert!(matched.params.is_empty());

// Match the dynamic route.
let matched = router.at("/hello")?;
assert_eq!(matched.params.get("hello"), Some("hello"));

Conflict Rules

Static and dynamic route segments are allowed to overlap. If they do, static segments will be given higher priority:

let mut router = Router::new();
router.insert("/", "Welcome!").unwrap();       // Priority: 1
router.insert("/about", "About Me").unwrap();  // Priority: 1
router.insert("/{*filepath}", "...").unwrap();  // Priority: 2

Formally, a route consists of a list of segments separated by /, with an optional leading and trailing slash: (/)<segment_1>/.../<segment_n>(/).

Given set of routes, their overlapping segments may include, in order of priority:

• Any number of static segments (/a, /b, …).
• One of the following:
  • Any number of route parameters with a suffix (/{x}a, /{x}b, …), prioritizing the longest suffix.
  • Any number of route parameters with a prefix (/a{x}, /b{x}, …), prioritizing the longest prefix.
  • A single route parameter with both a prefix and a suffix (/a{x}b).
• One of the following;
  • A single standalone parameter (/{x}).
  • A single standalone catch-all parameter (/{*rest}). Note this only applies to the final route segment.

Any other combination of route segments is considered ambiguous, and attempting to insert such a route will result in an error.

The one exception to the above set of rules is that catch-all parameters are always considered to conflict with suffixed route parameters, i.e. that /{*rest} and /{x}suffix are overlapping. This is due to an implementation detail of the routing tree that may be relaxed in the future.

How does it work?

The router takes advantage of the fact that URL routes generally follow a hierarchical structure. Routes are stored them in a radix trie that makes heavy use of common prefixes.

Priority   Path             Value
9          \                1
3          ├s               None
2          |├earch\         2
1          |└upport\        3
2          ├blog\           4
1          |    └{post}     None
1          |          └\    5
2          ├about-us\       6
1          |        └team\  7
1          └contact\        8

This allows us to reduce the route search to a small number of branches. Child nodes on the same level of the tree are also prioritized by the number of children with registered values, increasing the chance of choosing the correct branch of the first try.

As it turns out, this method of routing is extremely fast. See the benchmark results for details.

Structs

Match

A successful match consisting of the registered value and URL parameters, returned by Router::at.

MergeError

A failed merge attempt.

Params

A list of parameters returned by a route match.

ParamsIter

An iterator over the keys and values of a route’s parameters.

Router

A zero-copy URL router.

Enums

InsertError

Represents errors that can occur when inserting a new route.

MatchError

A failed match attempt.