1 files changed, 111 insertions, 0 deletions
diff --git a/third_party/rust/headers/src/common/if_match.rs b/third_party/rust/headers/src/common/if_match.rs
new file mode 100644
index 0000000000..5b9bdd95e3
--- /dev/null
+++ b/third_party/rust/headers/src/common/if_match.rs
@@ -0,0 +1,111 @@
+use super::ETag;
+use util::EntityTagRange;
+use HeaderValue;
+
+/// `If-Match` header, defined in
+/// [RFC7232](https://tools.ietf.org/html/rfc7232#section-3.1)
+///
+/// The `If-Match` header field makes the request method conditional on
+/// the recipient origin server either having at least one current
+/// representation of the target resource, when the field-value is "*",
+/// or having a current representation of the target resource that has an
+/// entity-tag matching a member of the list of entity-tags provided in
+/// the field-value.
+///
+/// An origin server MUST use the strong comparison function when
+/// comparing entity-tags for `If-Match`, since the client
+/// intends this precondition to prevent the method from being applied if
+/// there have been any changes to the representation data.
+///
+/// # ABNF
+///
+/// ```text
+/// If-Match = "*" / 1#entity-tag
+/// ```
+///
+/// # Example values
+///
+/// * `"xyzzy"`
+/// * "xyzzy", "r2d2xxxx", "c3piozzzz"
+///
+/// # Examples
+///
+/// ```
+/// # extern crate headers;
+/// use headers::IfMatch;
+///
+/// let if_match = IfMatch::any();
+/// ```
+#[derive(Clone, Debug, PartialEq)]
+pub struct IfMatch(EntityTagRange);
+
+derive_header! {
+    IfMatch(_),
+    name: IF_MATCH
+}
+
+impl IfMatch {
+    /// Create a new `If-Match: *` header.
+    pub fn any() -> IfMatch {
+        IfMatch(EntityTagRange::Any)
+    }
+
+    /// Returns whether this is `If-Match: *`, matching any entity tag.
+    pub fn is_any(&self) -> bool {
+        match self.0 {
+            EntityTagRange::Any => true,
+            EntityTagRange::Tags(..) => false,
+        }
+    }
+
+    /// Checks whether the `ETag` strongly matches.
+    pub fn precondition_passes(&self, etag: &ETag) -> bool {
+        self.0.matches_strong(&etag.0)
+    }
+}
+
+impl From<ETag> for IfMatch {
+    fn from(etag: ETag) -> IfMatch {
+        IfMatch(EntityTagRange::Tags(HeaderValue::from(etag.0).into()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_any() {
+        assert!(IfMatch::any().is_any());
+        assert!(!IfMatch::from(ETag::from_static("\"yolo\"")).is_any());
+    }
+
+    #[test]
+    fn precondition_fails() {
+        let if_match = IfMatch::from(ETag::from_static("\"foo\""));
+
+        let bar = ETag::from_static("\"bar\"");
+        let weak_foo = ETag::from_static("W/\"foo\"");
+
+        assert!(!if_match.precondition_passes(&bar));
+        assert!(!if_match.precondition_passes(&weak_foo));
+    }
+
+    #[test]
+    fn precondition_passes() {
+        let foo = ETag::from_static("\"foo\"");
+
+        let if_match = IfMatch::from(foo.clone());
+
+        assert!(if_match.precondition_passes(&foo));
+    }
+
+    #[test]
+    fn precondition_any() {
+        let foo = ETag::from_static("\"foo\"");
+
+        let if_match = IfMatch::any();
+
+        assert!(if_match.precondition_passes(&foo));
+    }
+}