add etag header

Author: ajnirp

src/header/common/etag.rs

@@ -0,0 +1,156 @@
+use header::{Header, HeaderFormat};
+use std::fmt::{mod};
+use super::util::from_one_raw_str;
+
+/// The `Etag` header.
+///
+/// An Etag consists of a string enclosed by two literal double quotes.
+/// Preceding the first double quote is an optional weakness indicator,
+/// which always looks like this: W/
+/// See also: https://tools.ietf.org/html/rfc7232#section-2.3
+#[deriving(Clone, PartialEq, Show)]
+pub struct Etag {
+    /// Weakness indicator for the tag
+    pub weak: bool,
+    /// The opaque string in between the DQUOTEs
+    pub tag: String
+}
+
+impl Header for Etag {
+    fn header_name(_: Option<Etag>) -> &'static str {
+        "Etag"
+    }
+
+    fn parse_header(raw: &[Vec<u8>]) -> Option<Etag> {
+        // check that each char in the slice is either:
+        // 1. %x21, or
+        // 2. in the range %x23 to %x7E, or
+        // 3. in the range %x80 to %xFF
+        fn check_slice_validity(slice: &str) -> bool {
+            for c in slice.bytes() {
+                match c {
+                    b'\x21' | b'\x23' ... b'\x7e' | b'\x80' ... b'\xff' => (),
+                    _ => { return false; }
+                }
+            }
+            true
+        }
+
+
+        from_one_raw_str(raw).and_then(|s: String| {
+            let length: uint = s.len();
+            let slice = s[];
+
+            // Early exits:
+            // 1. The string is empty, or,
+            // 2. it doesn't terminate in a DQUOTE.
+            if slice.is_empty() || !slice.ends_with("\"") {
+                return None;
+            }
+
+            // The etag is weak if its first char is not a DQUOTE.
+            if slice.char_at(0) == '"' {
+                // No need to check if the last char is a DQUOTE,
+                // we already did that above.
+                if check_slice_validity(slice.slice_chars(1, length-1)) {
+                    return Some(Etag {
+                        weak: false,
+                        tag: slice.slice_chars(1, length-1).into_string()
+                    });
+                } else {
+                    return None;
+                }
+            }
+
+            if slice.slice_chars(0, 3) == "W/\"" {
+                if check_slice_validity(slice.slice_chars(3, length-1)) {
+                    return Some(Etag {
+                        weak: true,
+                        tag: slice.slice_chars(3, length-1).into_string()
+                    });
+                } else {
+                    return None;
+                }
+            }
+
+            None
+        })
+    }
+}
+
+impl HeaderFormat for Etag {
+    fn fmt_header(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        if self.weak {
+            try!(fmt.write(b"W/"));
+        }
+        write!(fmt, "\"{}\"", self.tag)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Etag;
+    use header::Header;
+
+    #[test]
+    fn test_etag_successes() {
+        // Expected successes
+        let mut etag: Option<Etag>;
+
+        etag = Header::parse_header([b"\"foobar\"".to_vec()].as_slice());
+        assert_eq!(etag, Some(Etag {
+            weak: false,
+            tag: "foobar".into_string()
+        }));
+
+        etag = Header::parse_header([b"\"\"".to_vec()].as_slice());
+        assert_eq!(etag, Some(Etag {
+            weak: false,
+            tag: "".into_string()
+        }));
+
+        etag = Header::parse_header([b"W/\"weak-etag\"".to_vec()].as_slice());
+        assert_eq!(etag, Some(Etag {
+            weak: true,
+            tag: "weak-etag".into_string()
+        }));
+
+        etag = Header::parse_header([b"W/\"\x65\x62\"".to_vec()].as_slice());
+        assert_eq!(etag, Some(Etag {
+            weak: true,
+            tag: "\u0065\u0062".into_string()
+        }));
+
+        etag = Header::parse_header([b"W/\"\"".to_vec()].as_slice());
+        assert_eq!(etag, Some(Etag {
+            weak: true,
+            tag: "".into_string()
+        }));
+    }
+
+    #[test]
+    fn test_etag_failures() {
+        // Expected failures
+        let mut etag: Option<Etag>;
+
+        etag = Header::parse_header([b"no-dquotes".to_vec()].as_slice());
+        assert_eq!(etag, None);
+
+        etag = Header::parse_header([b"w/\"the-first-w-is-case-sensitive\"".to_vec()].as_slice());
+        assert_eq!(etag, None);
+
+        etag = Header::parse_header([b"".to_vec()].as_slice());
+        assert_eq!(etag, None);
+
+        etag = Header::parse_header([b"\"unmatched-dquotes1".to_vec()].as_slice());
+        assert_eq!(etag, None);
+
+        etag = Header::parse_header([b"unmatched-dquotes2\"".to_vec()].as_slice());
+        assert_eq!(etag, None);
+
+        etag = Header::parse_header([b"matched-\"dquotes\"".to_vec()].as_slice());
+        assert_eq!(etag, None);
+    }
+}
+
+bench_header!(bench, Etag, { vec![b"W/\"nonemptytag\"".to_vec()] })

src/header/common/mod.rs

@@ -14,6 +14,7 @@ pub use self::connection::Connection;
 pub use self::content_length::ContentLength;
 pub use self::content_type::ContentType;
 pub use self::date::Date;
+pub use self::etag::Etag;
 pub use self::expires::Expires;
 pub use self::host::Host;
 pub use self::last_modified::LastModified;
@@ -93,6 +94,9 @@ pub mod content_type;
 /// Exposes the Date header.
 pub mod date;
 
+/// Exposes the Etag header.
+pub mod etag;
+
 /// Exposes the Expires header.
 pub mod expires;