Macro async_coap_uri::rel_ref

macro_rules! rel_ref {
    ( unsafe $S:expr ) => { ... };
    ( $S:expr ) => { ... };
    ( ) => { ... };
}

Creates a &'static RelRef from a string literal.

Accepts only string constants and literals. The given string MUST be well-formed.

Example:

let x = rel_ref!("a/b/c?q=foobar#frag");
assert_eq!(x.raw_path(),"a/b/c");
assert_eq!(x.raw_query(),Some("q=foobar"));
assert_eq!(x.raw_fragment(),Some("frag"));

Checks for correctness are performed at compile time:

// This will not compile.
let x = rel_ref!("%00 invalid %ff");

Degenerate cases (strings that could be confused with URIs if parsed as URI-Refs) will also not compile:

// This will not compile because `//a/b/c` is
// a degenerate relative reference.
let x = rel_ref!("//a/b/c");

// This will not compile because `g:a:b:c` is
// a degenerate relative reference.
let x = rel_ref!("g:a:b:c");

Both of those cases can be made to compile by adjusting them to no longer be degenerate:

let b = rel_ref!("/.//a/b/c"); // Prepending "/."
let a = rel_ref!("./g:a:b:c"); // Prepending "./"
let a = rel_ref!("g%3Aa:b:c"); // Convert first colon to "%3A"

At runtime, UriRef::from_str("g:a:b:c") is allowed since in some circumstances it cannot be avoided, but there is usually no good reason to have a degenerate RelRef literal. In the rare case where such a thing is warranted (unit tests, for example), you can disable compile-time verification by prepending the keyword unsafe to the string:

// Both of these will compile because the `unsafe` keyword
// disables the compile-time validity checks:
assert!(rel_ref!(unsafe "//a/b/c").is_degenerate());
assert!(rel_ref!(unsafe "g:a:b:c").is_degenerate());