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use std::time::SystemTime;
use util::HttpDate;
/// `If-Modified-Since` header, defined in
///
/// The `If-Modified-Since` header field makes a GET or HEAD request
/// method conditional on the selected representation's modification date
/// being more recent than the date provided in the field-value.
/// Transfer of the selected representation's data is avoided if that
/// data has not changed.
///
/// # ABNF
///
/// ```text
/// If-Modified-Since = HTTP-date
/// ```
///
/// # Example values
/// * `Sat, 29 Oct 1994 19:43:31 GMT`
///
/// # Example
///
/// ```
/// # extern crate headers;
/// use headers::IfModifiedSince;
/// use std::time::{Duration, SystemTime};
///
/// let time = SystemTime::now() - Duration::from_secs(60 * 60 * 24);
/// let if_mod = IfModifiedSince::from(time);
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct IfModifiedSince(HttpDate);
derive_header! {
IfModifiedSince(_),
name: IF_MODIFIED_SINCE
}
impl IfModifiedSince {
/// Check if the supplied time means the resource has been modified.
pub fn is_modified(&self, last_modified: SystemTime) -> bool {
self.0 < last_modified.into()
}
}
impl From<SystemTime> for IfModifiedSince {
fn from(time: SystemTime) -> IfModifiedSince {
IfModifiedSince(time.into())
}
}
impl From<IfModifiedSince> for SystemTime {
fn from(date: IfModifiedSince) -> SystemTime {
date.0.into()
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::time::Duration;
#[test]
fn is_modified() {
let newer = SystemTime::now();
let exact = newer - Duration::from_secs(2);
let older = newer - Duration::from_secs(4);
let if_mod = IfModifiedSince::from(exact);
assert!(if_mod.is_modified(newer));
assert!(!if_mod.is_modified(exact));
assert!(!if_mod.is_modified(older));
}
}