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use std::time::SystemTime;
use util::HttpDate;
/// `If-Unmodified-Since` header, defined in
///
/// The `If-Unmodified-Since` header field makes the request method
/// conditional on the selected representation's last modification date
/// being earlier than or equal to the date provided in the field-value.
/// This field accomplishes the same purpose as If-Match for cases where
/// the user agent does not have an entity-tag for the representation.
///
/// # ABNF
///
/// ```text
/// If-Unmodified-Since = HTTP-date
/// ```
///
/// # Example values
///
/// * `Sat, 29 Oct 1994 19:43:31 GMT`
///
/// # Example
///
/// ```
/// # extern crate headers;
/// use headers::IfUnmodifiedSince;
/// use std::time::{SystemTime, Duration};
///
/// let time = SystemTime::now() - Duration::from_secs(60 * 60 * 24);
/// let if_unmod = IfUnmodifiedSince::from(time);
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct IfUnmodifiedSince(HttpDate);
derive_header! {
IfUnmodifiedSince(_),
name: IF_UNMODIFIED_SINCE
}
impl IfUnmodifiedSince {
/// Check if the supplied time passes the precondtion.
pub fn precondition_passes(&self, last_modified: SystemTime) -> bool {
self.0 >= last_modified.into()
}
}
impl From<SystemTime> for IfUnmodifiedSince {
fn from(time: SystemTime) -> IfUnmodifiedSince {
IfUnmodifiedSince(time.into())
}
}
impl From<IfUnmodifiedSince> for SystemTime {
fn from(date: IfUnmodifiedSince) -> SystemTime {
date.0.into()
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::time::Duration;
#[test]
fn precondition_passes() {
let newer = SystemTime::now();
let exact = newer - Duration::from_secs(2);
let older = newer - Duration::from_secs(4);
let if_unmod = IfUnmodifiedSince::from(exact);
assert!(!if_unmod.precondition_passes(newer));
assert!(if_unmod.precondition_passes(exact));
assert!(if_unmod.precondition_passes(older));
}
}