Macro oasis_cbor::destructure_cbor_map

macro_rules! destructure_cbor_map {
    ( let { $( $key:expr => $variable:ident, )+ } = $map:expr; ) => { ... };
}

This macro generates code to extract multiple values from a Vec<(Value, Value)> at once in an optimized manner, consuming the input vector.

It takes as input a Vec as well as a list of identifiers and keys, and generates code that assigns the corresponding values to new variables using the given identifiers. Each of these variables has type Option<Value>, to account for the case where keys aren’t found.

Important: Keys passed to the destructure_cbor_map! macro must be sorted in increasing order. If not, the algorithm can yield incorrect results, such a assigning None to a variable even if the corresponding key existed in the map. No runtime checks are made for this in the destructure_cbor_map! macro, in order to avoid overhead at runtime. However, assertions that keys are sorted are added in cfg(test) mode, so that unit tests can verify ahead of time that the keys are indeed sorted. This macro is therefore not suitable for dynamic keys that can change at runtime.

Example usage:

destructure_cbor_map! {
    let {
        1 => x,
        "key" => y,
    } = map;
}