feat: add method to check if AcceptRanges is bytes (#159)

Author: tottoto

src/common/accept_ranges.rs

@@ -1,3 +1,5 @@
+use http::HeaderValue;
+
 use util::FlatCsv;
 
 /// `Accept-Ranges` header, defined in [RFC7233](http://tools.ietf.org/html/rfc7233#section-2.3)
@@ -34,9 +36,33 @@ derive_header! {
     name: ACCEPT_RANGES
 }
 
+const ACCEPT_RANGES_BYTES: HeaderValue = ::HeaderValue::from_static("bytes");
+
 impl AcceptRanges {
     /// A constructor to easily create the common `Accept-Ranges: bytes` header.
     pub fn bytes() -> Self {
-        AcceptRanges(::HeaderValue::from_static("bytes").into())
+        AcceptRanges(ACCEPT_RANGES_BYTES.into())
+    }
+
+    /// Check if the unit is `bytes`.
+    pub fn is_bytes(&self) -> bool {
+        self.0.value == ACCEPT_RANGES_BYTES
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn bytes() {
+        let bytes_range = AcceptRanges::bytes();
+        assert!(bytes_range.is_bytes());
+    }
+
+    #[test]
+    fn bytes_fails() {
+        let none_range = AcceptRanges(::HeaderValue::from_static("none").into());
+        assert!(!none_range.is_bytes());
     }
 }