add a structured cache::Age header

src/cache/age.rs

@@ -0,0 +1,117 @@
+use crate::headers::{HeaderName, HeaderValue, Headers, ToHeaderValues, AGE};
+use crate::Status;
+
+use std::fmt::Debug;
+use std::option;
+use std::time::Duration;
+
+/// HTTP `Age` header
+///
+/// # Specifications
+///
+/// - [RFC 7234 Hypertext Transfer Protocol (HTTP/1.1): Caching](https://tools.ietf.org/html/rfc7234#section-5.1)
+///
+/// # Examples
+///
+/// ```
+/// # fn main() -> http_types::Result<()> {
+/// #
+/// use http_types::Response;
+/// use http_types::cache::Age;
+/// use std::time::Duration;
+///
+/// let age = Age::new(Duration::from_secs(12));
+///
+/// let mut res = Response::new(200);
+/// age.apply(&mut res);
+///
+/// let age = Age::from_headers(res)?.unwrap();
+/// assert_eq!(age, Age::new(Duration::from_secs(12)));
+/// #
+/// # Ok(()) }
+/// ```
+#[derive(Debug, Ord, PartialOrd, Eq, PartialEq)]
+pub struct Age {
+ dur: Duration,
+}
+
+impl Age {
+ /// Create a new instance of `Age`.
+ pub fn new(dur: Duration) -> Self {
+ Self { dur }
+ }
+
+ /// Create an instance of `Age` from a `Headers` instance.
+ ///
+ /// # Implementation note
+ ///
+ /// A header value of `"null"` is treated the same as if no header was sent.
+ pub fn from_headers(headers: impl AsRef<Headers>) -> crate::Result<Option<Self>> {
+ let headers = match headers.as_ref().get(AGE) {
+ Some(headers) => headers,
+ None => return Ok(None),
+ };
+
+ // If we successfully parsed the header then there's always at least one
+ // entry. We want the last entry.
+ let header = headers.iter().last().unwrap();
+
+ let num: u64 = header.as_str().parse().status(400)?;
+ let dur = Duration::from_secs_f64(num as f64);
+
+ Ok(Some(Self { dur }))
+ }
+
+ /// Insert a `HeaderName` + `HeaderValue` pair into a `Headers` instance.
+ pub fn apply(&self, mut headers: impl AsMut<Headers>) {
+ headers.as_mut().insert(AGE, self.value());
+ }
+
+ /// Get the `HeaderName`.
+ pub fn name(&self) -> HeaderName {
+ AGE
+ }
+
+ /// Get the `HeaderValue`.
+ pub fn value(&self) -> HeaderValue {
+ let output = self.dur.as_secs().to_string();
+
+ // SAFETY: the internal string is validated to be ASCII.
+ unsafe { HeaderValue::from_bytes_unchecked(output.into()) }
+ }
+}
+
+impl ToHeaderValues for Age {
+ type Iter = option::IntoIter<HeaderValue>;
+ fn to_header_values(&self) -> crate::Result<Self::Iter> {
+ // A HeaderValue will always convert into itself.
+ Ok(self.value().to_header_values().unwrap())
+ }
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+ use crate::headers::Headers;
+
+ #[test]
+ fn smoke() -> crate::Result<()> {
+ let age = Age::new(Duration::from_secs(12));
+
+ let mut headers = Headers::new();
+ age.apply(&mut headers);
+
+ let age = Age::from_headers(headers)?.unwrap();
+ assert_eq!(age, Age::new(Duration::from_secs(12)));
+ Ok(())
+ }
+
+ #[test]
+ fn bad_request_on_parse_error() -> crate::Result<()> {
+ let mut headers = Headers::new();
+ headers.insert(AGE, "<nori ate the tag. yum.>");
+ let err = Age::from_headers(headers).unwrap_err();
+ assert_eq!(err.status(), 400);
+ Ok(())
+ }
+}

src/cache/mod.rs

@@ -10,6 +10,8 @@
 //! - [MDN: HTTP Conditional Requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Conditional_requests)
 
 mod cache_control;
+mod age;
 
 pub use cache_control::CacheControl;
 pub use cache_control::CacheDirective;
+pub use age::Age;