From 195a89fa918a83c9dcab47a4b09edb464d4e8006 Mon Sep 17 00:00:00 2001
From: Pyfisch <pyfisch@gmail.com>
Date: Sat, 6 Jun 2015 22:04:01 +0200
Subject: [PATCH] refactor(headers): errors for parse_header

Header::parse_header() returns now a hyper Result instead of an option
this will enable more precise Error messages in the future, currently
most failures are reported as ::Error::Header.

BREAKING CHANGE: parse_header returns Result instead of Option, related
code did also change
---
 benches/client.rs                             |  5 +--
 src/error.rs                                  | 11 +++++
 src/header/common/accept_ranges.rs            |  4 +-
 .../common/access_control_allow_origin.rs     | 12 +++---
 src/header/common/authorization.rs            | 37 +++++++++-------
 src/header/common/cache_control.rs            | 20 ++++-----
 src/header/common/cookie.rs                   | 27 ++++++------
 src/header/common/expect.rs                   |  8 ++--
 src/header/common/host.rs                     | 10 ++---
 src/header/common/if_none_match.rs            |  6 +--
 src/header/common/if_range.rs                 | 16 +++----
 src/header/common/mod.rs                      | 12 +++---
 src/header/common/pragma.rs                   | 10 ++---
 src/header/common/set_cookie.rs               |  8 ++--
 src/header/common/upgrade.rs                  |  4 +-
 src/header/common/vary.rs                     | 10 ++---
 src/header/internals/item.rs                  | 10 ++---
 src/header/mod.rs                             | 19 ++++----
 src/header/parsing.rs                         | 43 ++++++++-----------
 19 files changed, 140 insertions(+), 132 deletions(-)

diff --git a/benches/client.rs b/benches/client.rs
index 984ce13191..ff11a712ca 100644
--- a/benches/client.rs
+++ b/benches/client.rs
@@ -58,8 +58,8 @@ impl hyper::header::Header for Foo {
     fn header_name() -> &'static str {
         "x-foo"
     }
-    fn parse_header(_: &[Vec<u8>]) -> Option<Foo> {
-        None
+    fn parse_header(_: &[Vec<u8>]) -> hyper::Result<Foo> {
+        Err(hyper::Error::Header)
     }
 }
 
@@ -104,4 +104,3 @@ fn bench_mock_hyper(b: &mut test::Bencher) {
             .read_to_string(&mut s).unwrap()
     });
 }
-
diff --git a/src/error.rs b/src/error.rs
index 96844f45d0..762f29e66a 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -2,6 +2,7 @@
 use std::error::Error as StdError;
 use std::fmt;
 use std::io::Error as IoError;
+use std::str::Utf8Error;
 
 use httparse;
 use openssl::ssl::error::SslError;
@@ -18,6 +19,7 @@ use self::Error::{
     Ssl,
     TooLarge,
     Http2,
+    Utf8
 };
 
 
@@ -45,6 +47,8 @@ pub enum Error {
     Ssl(SslError),
     /// An HTTP/2-specific error, coming from the `solicit` library.
     Http2(Http2Error),
+    /// Parsing a field as string failed
+    Utf8(Utf8Error),
 
     #[doc(hidden)]
     __Nonexhaustive(Void)
@@ -77,6 +81,7 @@ impl StdError for Error {
             Io(ref e) => e.description(),
             Ssl(ref e) => e.description(),
             Http2(ref e) => e.description(),
+            Utf8(ref e) => e.description(),
             Error::__Nonexhaustive(ref void) =>  match *void {}
         }
     }
@@ -113,6 +118,12 @@ impl From<SslError> for Error {
     }
 }
 
+impl From<Utf8Error> for Error {
+    fn from(err: Utf8Error) -> Error {
+        Utf8(err)
+    }
+}
+
 impl From<httparse::Error> for Error {
     fn from(err: httparse::Error) -> Error {
         match err {
diff --git a/src/header/common/accept_ranges.rs b/src/header/common/accept_ranges.rs
index 9b15bbd548..ffcceeeb9d 100644
--- a/src/header/common/accept_ranges.rs
+++ b/src/header/common/accept_ranges.rs
@@ -52,8 +52,8 @@ pub enum RangeUnit {
 
 
 impl FromStr for RangeUnit {
-    type Err = ();
-    fn from_str(s: &str) -> Result<Self, ()> {
+    type Err = ::Error;
+    fn from_str(s: &str) -> ::Result<Self> {
         match s {
             "bytes" => Ok(RangeUnit::Bytes),
             "none" => Ok(RangeUnit::None),
diff --git a/src/header/common/access_control_allow_origin.rs b/src/header/common/access_control_allow_origin.rs
index 06d758e3e2..fff5ff3d20 100644
--- a/src/header/common/access_control_allow_origin.rs
+++ b/src/header/common/access_control_allow_origin.rs
@@ -35,16 +35,14 @@ impl Header for AccessControlAllowOrigin {
         "Access-Control-Allow-Origin"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<AccessControlAllowOrigin> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<AccessControlAllowOrigin> {
         if raw.len() == 1 {
             match unsafe { &raw.get_unchecked(0)[..] } {
-                b"*" => Some(AccessControlAllowOrigin::Any),
-                b"null" => Some(AccessControlAllowOrigin::Null),
-                r => if let Ok(s) = str::from_utf8(r) {
-                    Url::parse(s).ok().map(AccessControlAllowOrigin::Value)
-                } else { None }
+                b"*" => Ok(AccessControlAllowOrigin::Any),
+                b"null" => Ok(AccessControlAllowOrigin::Null),
+                r => Ok(AccessControlAllowOrigin::Value(try!(Url::parse(try!(str::from_utf8(r))))))
             }
-        } else { None }
+        } else { Err(::Error::Header) }
     }
 }
 
diff --git a/src/header/common/authorization.rs b/src/header/common/authorization.rs
index f5a05073ed..f7724cbae1 100644
--- a/src/header/common/authorization.rs
+++ b/src/header/common/authorization.rs
@@ -42,18 +42,25 @@ impl<S: Scheme + Any> Header for Authorization<S> where <S as FromStr>::Err: 'st
         "Authorization"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Authorization<S>> {
-        if raw.len() == 1 {
-            match (from_utf8(unsafe { &raw.get_unchecked(0)[..] }), <S as Scheme>::scheme()) {
-                (Ok(header), Some(scheme))
-                    if header.starts_with(scheme) && header.len() > scheme.len() + 1 => {
-                    header[scheme.len() + 1..].parse::<S>().map(Authorization).ok()
-                },
-                (Ok(header), None) => header.parse::<S>().map(Authorization).ok(),
-                _ => None
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Authorization<S>> {
+        if raw.len() != 1 {
+            return Err(::Error::Header);
+        }
+        let header = try!(from_utf8(unsafe { &raw.get_unchecked(0)[..] }));
+        return if let Some(scheme) = <S as Scheme>::scheme() {
+            if header.starts_with(scheme) && header.len() > scheme.len() + 1 {
+                match header[scheme.len() + 1..].parse::<S>().map(Authorization) {
+                    Ok(h) => Ok(h),
+                    Err(_) => Err(::Error::Header)
+                }
+            } else {
+                Err(::Error::Header)
             }
         } else {
-            None
+            match header.parse::<S>().map(Authorization) {
+                Ok(h) => Ok(h),
+                Err(_) => Err(::Error::Header)
+            }
         }
     }
 }
@@ -121,15 +128,15 @@ impl Scheme for Basic {
 }
 
 impl FromStr for Basic {
-    type Err = ();
-    fn from_str(s: &str) -> Result<Basic, ()> {
+    type Err = ::Error;
+    fn from_str(s: &str) -> ::Result<Basic> {
         match s.from_base64() {
             Ok(decoded) => match String::from_utf8(decoded) {
                 Ok(text) => {
                     let mut parts = &mut text.split(':');
                     let user = match parts.next() {
                         Some(part) => part.to_owned(),
-                        None => return Err(())
+                        None => return Err(::Error::Header)
                     };
                     let password = match parts.next() {
                         Some(part) => Some(part.to_owned()),
@@ -142,12 +149,12 @@ impl FromStr for Basic {
                 },
                 Err(e) => {
                     debug!("Basic::from_utf8 error={:?}", e);
-                    Err(())
+                    Err(::Error::Header)
                 }
             },
             Err(e) => {
                 debug!("Basic::from_base64 error={:?}", e);
-                Err(())
+                Err(::Error::Header)
             }
         }
     }
diff --git a/src/header/common/cache_control.rs b/src/header/common/cache_control.rs
index ab7dd6cac8..c937c01848 100644
--- a/src/header/common/cache_control.rs
+++ b/src/header/common/cache_control.rs
@@ -30,15 +30,15 @@ impl Header for CacheControl {
         "Cache-Control"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<CacheControl> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<CacheControl> {
         let directives = raw.iter()
-            .filter_map(|line| from_one_comma_delimited(&line[..]))
+            .filter_map(|line| from_one_comma_delimited(&line[..]).ok())
             .collect::<Vec<Vec<CacheDirective>>>()
             .concat();
         if !directives.is_empty() {
-            Some(CacheControl(directives))
+            Ok(CacheControl(directives))
         } else {
-            None
+            Err(::Error::Header)
         }
     }
 }
@@ -148,35 +148,35 @@ mod tests {
     #[test]
     fn test_parse_multiple_headers() {
         let cache = Header::parse_header(&[b"no-cache".to_vec(), b"private".to_vec()]);
-        assert_eq!(cache, Some(CacheControl(vec![CacheDirective::NoCache,
+        assert_eq!(cache.ok(), Some(CacheControl(vec![CacheDirective::NoCache,
                                                  CacheDirective::Private])))
     }
 
     #[test]
     fn test_parse_argument() {
         let cache = Header::parse_header(&[b"max-age=100, private".to_vec()]);
-        assert_eq!(cache, Some(CacheControl(vec![CacheDirective::MaxAge(100),
+        assert_eq!(cache.ok(), Some(CacheControl(vec![CacheDirective::MaxAge(100),
                                                  CacheDirective::Private])))
     }
 
     #[test]
     fn test_parse_quote_form() {
         let cache = Header::parse_header(&[b"max-age=\"200\"".to_vec()]);
-        assert_eq!(cache, Some(CacheControl(vec![CacheDirective::MaxAge(200)])))
+        assert_eq!(cache.ok(), Some(CacheControl(vec![CacheDirective::MaxAge(200)])))
     }
 
     #[test]
     fn test_parse_extension() {
         let cache = Header::parse_header(&[b"foo, bar=baz".to_vec()]);
-        assert_eq!(cache, Some(CacheControl(vec![
+        assert_eq!(cache.ok(), Some(CacheControl(vec![
             CacheDirective::Extension("foo".to_owned(), None),
             CacheDirective::Extension("bar".to_owned(), Some("baz".to_owned()))])))
     }
 
     #[test]
     fn test_parse_bad_syntax() {
-        let cache: Option<CacheControl> = Header::parse_header(&[b"foo=".to_vec()]);
-        assert_eq!(cache, None)
+        let cache: ::Result<CacheControl> = Header::parse_header(&[b"foo=".to_vec()]);
+        assert_eq!(cache.ok(), None)
     }
 }
 
diff --git a/src/header/common/cookie.rs b/src/header/common/cookie.rs
index 6322c400c3..07ff710a5e 100644
--- a/src/header/common/cookie.rs
+++ b/src/header/common/cookie.rs
@@ -27,26 +27,23 @@ impl Header for Cookie {
         "Cookie"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Cookie> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Cookie> {
         let mut cookies = Vec::with_capacity(raw.len());
         for cookies_raw in raw.iter() {
-            match from_utf8(&cookies_raw[..]) {
-                Ok(cookies_str) => {
-                    for cookie_str in cookies_str.split(';') {
-                        match cookie_str.trim().parse() {
-                            Ok(cookie) => cookies.push(cookie),
-                            Err(_) => return None
-                        }
-                    }
-                },
-                Err(_) => return None
-            };
+            let cookies_str = try!(from_utf8(&cookies_raw[..]));
+            for cookie_str in cookies_str.split(';') {
+                if let Ok(cookie) = cookie_str.trim().parse() {
+                    cookies.push(cookie);
+                } else {
+                    return Err(::Error::Header);
+                }
+            }
         }
 
         if !cookies.is_empty() {
-            Some(Cookie(cookies))
+            Ok(Cookie(cookies))
         } else {
-            None
+            Err(::Error::Header)
         }
     }
 }
@@ -88,7 +85,7 @@ fn test_parse() {
     let h = Header::parse_header(&[b"foo=bar; baz=quux".to_vec()][..]);
     let c1 = CookiePair::new("foo".to_owned(), "bar".to_owned());
     let c2 = CookiePair::new("baz".to_owned(), "quux".to_owned());
-    assert_eq!(h, Some(Cookie(vec![c1, c2])));
+    assert_eq!(h.ok(), Some(Cookie(vec![c1, c2])));
 }
 
 #[test]
diff --git a/src/header/common/expect.rs b/src/header/common/expect.rs
index 0bb9eac601..109ce70723 100644
--- a/src/header/common/expect.rs
+++ b/src/header/common/expect.rs
@@ -26,7 +26,7 @@ impl Header for Expect {
         "Expect"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Expect> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Expect> {
         if raw.len() == 1 {
             let text = unsafe {
                 // safe because:
@@ -38,12 +38,12 @@ impl Header for Expect {
                 str::from_utf8_unchecked(raw.get_unchecked(0))
             };
             if UniCase(text) == EXPECT_CONTINUE {
-                Some(Expect::Continue)
+                Ok(Expect::Continue)
             } else {
-                None
+                Err(::Error::Header)
             }
         } else {
-            None
+            Err(::Error::Header)
         }
     }
 }
diff --git a/src/header/common/host.rs b/src/header/common/host.rs
index 2984f27c32..4f628dc638 100644
--- a/src/header/common/host.rs
+++ b/src/header/common/host.rs
@@ -22,7 +22,7 @@ impl Header for Host {
         "Host"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Host> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Host> {
         from_one_raw_str(raw).and_then(|mut s: String| {
             // FIXME: use rust-url to parse this
             // https://github.com/servo/rust-url/issues/42
@@ -39,7 +39,7 @@ impl Header for Host {
                                 None
                             }
                         }
-                        None => return None // this is a bad ipv6 address...
+                        None => return Err(::Error::Header) // this is a bad ipv6 address...
                     }
                 } else {
                     slice.rfind(':')
@@ -56,7 +56,7 @@ impl Header for Host {
                 None => ()
             }
 
-            Some(Host {
+            Ok(Host {
                 hostname: s,
                 port: port
             })
@@ -82,14 +82,14 @@ mod tests {
     #[test]
     fn test_host() {
         let host = Header::parse_header([b"foo.com".to_vec()].as_ref());
-        assert_eq!(host, Some(Host {
+        assert_eq!(host.ok(), Some(Host {
             hostname: "foo.com".to_owned(),
             port: None
         }));
 
 
         let host = Header::parse_header([b"foo.com:8080".to_vec()].as_ref());
-        assert_eq!(host, Some(Host {
+        assert_eq!(host.ok(), Some(Host {
             hostname: "foo.com".to_owned(),
             port: Some(8080)
         }));
diff --git a/src/header/common/if_none_match.rs b/src/header/common/if_none_match.rs
index 7d801045bb..8fb249d526 100644
--- a/src/header/common/if_none_match.rs
+++ b/src/header/common/if_none_match.rs
@@ -45,10 +45,10 @@ mod tests {
 
     #[test]
     fn test_if_none_match() {
-        let mut if_none_match: Option<IfNoneMatch>;
+        let mut if_none_match: ::Result<IfNoneMatch>;
 
         if_none_match = Header::parse_header([b"*".to_vec()].as_ref());
-        assert_eq!(if_none_match, Some(IfNoneMatch::Any));
+        assert_eq!(if_none_match.ok(), Some(IfNoneMatch::Any));
 
         if_none_match = Header::parse_header([b"\"foobar\", W/\"weak-etag\"".to_vec()].as_ref());
         let mut entities: Vec<EntityTag> = Vec::new();
@@ -56,7 +56,7 @@ mod tests {
         let weak_etag = EntityTag::new(true, "weak-etag".to_owned());
         entities.push(foobar_etag);
         entities.push(weak_etag);
-        assert_eq!(if_none_match, Some(IfNoneMatch::Items(entities)));
+        assert_eq!(if_none_match.ok(), Some(IfNoneMatch::Items(entities)));
     }
 }
 
diff --git a/src/header/common/if_range.rs b/src/header/common/if_range.rs
index c3b0f12029..1f02e53966 100644
--- a/src/header/common/if_range.rs
+++ b/src/header/common/if_range.rs
@@ -36,16 +36,16 @@ impl Header for IfRange {
     fn header_name() -> &'static str {
         "If-Range"
     }
-    fn parse_header(raw: &[Vec<u8>]) -> Option<IfRange> {
-        let etag: Option<EntityTag> = header::parsing::from_one_raw_str(raw);
-        if etag != None {
-            return Some(IfRange::EntityTag(etag.unwrap()));
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<IfRange> {
+        let etag: ::Result<EntityTag> = header::parsing::from_one_raw_str(raw);
+        if etag.is_ok() {
+            return Ok(IfRange::EntityTag(etag.unwrap()));
         }
-        let date: Option<HttpDate> = header::parsing::from_one_raw_str(raw);
-        if date != None {
-            return Some(IfRange::Date(date.unwrap()));
+        let date: ::Result<HttpDate> = header::parsing::from_one_raw_str(raw);
+        if date.is_ok() {
+            return Ok(IfRange::Date(date.unwrap()));
         }
-        None
+        Err(::Error::Header)
     }
 }
 
diff --git a/src/header/common/mod.rs b/src/header/common/mod.rs
index 79f9cc3585..987efc3701 100644
--- a/src/header/common/mod.rs
+++ b/src/header/common/mod.rs
@@ -144,7 +144,7 @@ macro_rules! test_header {
             let a: Vec<Vec<u8>> = $raw.iter().map(|x| x.to_vec()).collect();
             let val = HeaderField::parse_header(&a[..]);
             // Test parsing
-            assert_eq!(val, $typed);
+            assert_eq!(val.ok(), $typed);
             // Test formatting
             if $typed != None {
                 let res: &str = str::from_utf8($raw[0]).unwrap();
@@ -171,7 +171,7 @@ macro_rules! header {
             fn header_name() -> &'static str {
                 $n
             }
-            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+            fn parse_header(raw: &[Vec<u8>]) -> $crate::Result<Self> {
                 $crate::header::parsing::from_comma_delimited(raw).map($id)
             }
         }
@@ -197,7 +197,7 @@ macro_rules! header {
             fn header_name() -> &'static str {
                 $n
             }
-            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+            fn parse_header(raw: &[Vec<u8>]) -> $crate::Result<Self> {
                 $crate::header::parsing::from_comma_delimited(raw).map($id)
             }
         }
@@ -223,7 +223,7 @@ macro_rules! header {
             fn header_name() -> &'static str {
                 $n
             }
-            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+            fn parse_header(raw: &[Vec<u8>]) -> $crate::Result<Self> {
                 $crate::header::parsing::from_one_raw_str(raw).map($id)
             }
         }
@@ -252,11 +252,11 @@ macro_rules! header {
             fn header_name() -> &'static str {
                 $n
             }
-            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+            fn parse_header(raw: &[Vec<u8>]) -> $crate::Result<Self> {
                 // FIXME: Return None if no item is in $id::Only
                 if raw.len() == 1 {
                     if raw[0] == b"*" {
-                        return Some($id::Any)
+                        return Ok($id::Any)
                     }
                 }
                 $crate::header::parsing::from_comma_delimited(raw).map(|vec| $id::Items(vec))
diff --git a/src/header/common/pragma.rs b/src/header/common/pragma.rs
index 21b0c0db04..50e82966ca 100644
--- a/src/header/common/pragma.rs
+++ b/src/header/common/pragma.rs
@@ -29,12 +29,12 @@ impl Header for Pragma {
         "Pragma"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Pragma> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Pragma> {
         parsing::from_one_raw_str(raw).and_then(|s: String| {
             let slice = &s.to_ascii_lowercase()[..];
             match slice {
-                "no-cache" => Some(Pragma::NoCache),
-                _ => Some(Pragma::Ext(s)),
+                "no-cache" => Ok(Pragma::NoCache),
+                _ => Ok(Pragma::Ext(s)),
             }
         })
     }
@@ -57,6 +57,6 @@ fn test_parse_header() {
     let c: Pragma = Header::parse_header([b"FoObar".to_vec()].as_ref()).unwrap();
     let d = Pragma::Ext("FoObar".to_owned());
     assert_eq!(c, d);
-    let e: Option<Pragma> = Header::parse_header([b"".to_vec()].as_ref());
-    assert_eq!(e, None);
+    let e: ::Result<Pragma> = Header::parse_header([b"".to_vec()].as_ref());
+    assert_eq!(e.ok(), None);
 }
diff --git a/src/header/common/set_cookie.rs b/src/header/common/set_cookie.rs
index 8177fb49a7..a2b02f1e7b 100644
--- a/src/header/common/set_cookie.rs
+++ b/src/header/common/set_cookie.rs
@@ -64,7 +64,7 @@ impl Header for SetCookie {
         "Set-Cookie"
     }
 
-    fn parse_header(raw: &[Vec<u8>]) -> Option<SetCookie> {
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<SetCookie> {
         let mut set_cookies = Vec::with_capacity(raw.len());
         for set_cookies_raw in raw {
             if let Ok(s) = from_utf8(&set_cookies_raw[..]) {
@@ -75,9 +75,9 @@ impl Header for SetCookie {
         }
 
         if !set_cookies.is_empty() {
-            Some(SetCookie(set_cookies))
+            Ok(SetCookie(set_cookies))
         } else {
-            None
+            Err(::Error::Header)
         }
     }
 
@@ -120,7 +120,7 @@ fn test_parse() {
     let mut c1 = Cookie::new("foo".to_owned(), "bar".to_owned());
     c1.httponly = true;
 
-    assert_eq!(h, Some(SetCookie(vec![c1])));
+    assert_eq!(h.ok(), Some(SetCookie(vec![c1])));
 }
 
 #[test]
diff --git a/src/header/common/upgrade.rs b/src/header/common/upgrade.rs
index 69bccd02f2..5ae7cf7146 100644
--- a/src/header/common/upgrade.rs
+++ b/src/header/common/upgrade.rs
@@ -45,8 +45,8 @@ header! {
             Some(Upgrade(vec![Protocol::new(ProtocolName::WebSocket, None)])));
         #[test]
         fn test3() {
-            let x: Option<Upgrade> = Header::parse_header(&[b"WEbSOCKet".to_vec()]);
-            assert_eq!(x, Some(Upgrade(vec![Protocol::new(ProtocolName::WebSocket, None)])));
+            let x: ::Result<Upgrade> = Header::parse_header(&[b"WEbSOCKet".to_vec()]);
+            assert_eq!(x.ok(), Some(Upgrade(vec![Protocol::new(ProtocolName::WebSocket, None)])));
         }
     }
 }
diff --git a/src/header/common/vary.rs b/src/header/common/vary.rs
index 65a32725d5..d49058add9 100644
--- a/src/header/common/vary.rs
+++ b/src/header/common/vary.rs
@@ -24,15 +24,15 @@ header! {
 
         #[test]
         fn test2() {
-            let mut vary: Option<Vary>;
+            let mut vary: ::Result<Vary>;
 
             vary = Header::parse_header([b"*".to_vec()].as_ref());
-            assert_eq!(vary, Some(Vary::Any));
+            assert_eq!(vary.ok(), Some(Vary::Any));
 
             vary = Header::parse_header([b"etag,cookie,allow".to_vec()].as_ref());
-            assert_eq!(vary, Some(Vary::Items(vec!["eTag".parse().unwrap(),
-                                                    "cookIE".parse().unwrap(),
-                                                    "AlLOw".parse().unwrap(),])));
+            assert_eq!(vary.ok(), Some(Vary::Items(vec!["eTag".parse().unwrap(),
+                                                        "cookIE".parse().unwrap(),
+                                                        "AlLOw".parse().unwrap(),])));
         }
     }
 }
diff --git a/src/header/internals/item.rs b/src/header/internals/item.rs
index b9afa8f575..81a637436d 100644
--- a/src/header/internals/item.rs
+++ b/src/header/internals/item.rs
@@ -60,11 +60,11 @@ impl Item {
             Some(val) => Some(val),
             None => {
                 match parse::<H>(self.raw.as_ref().expect("item.raw must exist")) {
-                    Some(typed) => {
+                    Ok(typed) => {
                         unsafe { self.typed.insert(tid, typed); }
                         self.typed.get(tid)
                     },
-                    None => None
+                    Err(_) => None
                 }
             }
         }.map(|typed| unsafe { typed.downcast_ref_unchecked() })
@@ -74,10 +74,10 @@ impl Item {
         let tid = TypeId::of::<H>();
         if self.typed.get_mut(tid).is_none() {
             match parse::<H>(self.raw.as_ref().expect("item.raw must exist")) {
-                Some(typed) => {
+                Ok(typed) => {
                     unsafe { self.typed.insert(tid, typed); }
                 },
-                None => ()
+                Err(_) => ()
             }
         }
         self.typed.get_mut(tid).map(|typed| unsafe { typed.downcast_mut_unchecked() })
@@ -85,7 +85,7 @@ impl Item {
 }
 
 #[inline]
-fn parse<H: Header + HeaderFormat>(raw: &Vec<Vec<u8>>) -> Option<Box<HeaderFormat + Send + Sync>> {
+fn parse<H: Header + HeaderFormat>(raw: &Vec<Vec<u8>>) -> ::Result<Box<HeaderFormat + Send + Sync>> {
     Header::parse_header(&raw[..]).map(|h: H| {
         // FIXME: Use Type ascription
         let h: Box<HeaderFormat + Send + Sync> = Box::new(h);
diff --git a/src/header/mod.rs b/src/header/mod.rs
index 43b1ec47e2..087ff1e64f 100644
--- a/src/header/mod.rs
+++ b/src/header/mod.rs
@@ -44,7 +44,7 @@ pub trait Header: Clone + Any + Send + Sync {
     /// it's not necessarily the case that a Header is *allowed* to have more
     /// than one field value. If that's the case, you **should** return `None`
     /// if `raw.len() > 1`.
-    fn parse_header(raw: &[Vec<u8>]) -> Option<Self>;
+    fn parse_header(raw: &[Vec<u8>]) -> ::Result<Self>;
 
 }
 
@@ -420,7 +420,7 @@ mod tests {
     #[test]
     fn test_content_type() {
         let content_type = Header::parse_header([b"text/plain".to_vec()].as_ref());
-        assert_eq!(content_type, Some(ContentType(Mime(Text, Plain, vec![]))));
+        assert_eq!(content_type.ok(), Some(ContentType(Mime(Text, Plain, vec![]))));
     }
 
     #[test]
@@ -429,10 +429,10 @@ mod tests {
         let application_vendor = "application/vnd.github.v3.full+json; q=0.5".parse().unwrap();
 
         let accept = Header::parse_header([b"text/plain".to_vec()].as_ref());
-        assert_eq!(accept, Some(Accept(vec![text_plain.clone()])));
+        assert_eq!(accept.ok(), Some(Accept(vec![text_plain.clone()])));
 
         let accept = Header::parse_header([b"application/vnd.github.v3.full+json; q=0.5, text/plain".to_vec()].as_ref());
-        assert_eq!(accept, Some(Accept(vec![application_vendor, text_plain])));
+        assert_eq!(accept.ok(), Some(Accept(vec![application_vendor, text_plain])));
     }
 
     #[derive(Clone, PartialEq, Debug)]
@@ -442,18 +442,21 @@ mod tests {
         fn header_name() -> &'static str {
             "content-length"
         }
-        fn parse_header(raw: &[Vec<u8>]) -> Option<CrazyLength> {
+        fn parse_header(raw: &[Vec<u8>]) -> ::Result<CrazyLength> {
             use std::str::from_utf8;
             use std::str::FromStr;
 
             if raw.len() != 1 {
-                return None;
+                return Err(::Error::Header);
             }
             // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
-            match from_utf8(unsafe { &raw.get_unchecked(0)[..] }) {
+            match match from_utf8(unsafe { &raw.get_unchecked(0)[..] }) {
                 Ok(s) => FromStr::from_str(s).ok(),
                 Err(_) => None
-            }.map(|u| CrazyLength(Some(false), u))
+            }.map(|u| CrazyLength(Some(false), u)) {
+                Some(x) => Ok(x),
+                None => Err(::Error::Header),
+            }
         }
     }
 
diff --git a/src/header/parsing.rs b/src/header/parsing.rs
index 5d4744de49..5a4e572839 100644
--- a/src/header/parsing.rs
+++ b/src/header/parsing.rs
@@ -4,44 +4,37 @@ use std::str;
 use std::fmt::{self, Display};
 
 /// Reads a single raw string when parsing a header
-pub fn from_one_raw_str<T: str::FromStr>(raw: &[Vec<u8>]) -> Option<T> {
-    if raw.len() != 1 {
-        return None;
-    }
+pub fn from_one_raw_str<T: str::FromStr>(raw: &[Vec<u8>]) -> ::Result<T> {
+    if raw.len() != 1 || unsafe { raw.get_unchecked(0) } == b"" { return Err(::Error::Header) }
     // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
-    if let Ok(s) = str::from_utf8(& unsafe { raw.get_unchecked(0) }[..]) {
-        if s != "" {
-            return str::FromStr::from_str(s).ok();
-        }
+    let s: &str = try!(str::from_utf8(& unsafe { raw.get_unchecked(0) }[..]));
+    if let Ok(x) = str::FromStr::from_str(s) {
+        Ok(x)
+    } else {
+        Err(::Error::Header)
     }
-    None
 }
 
 /// Reads a comma-delimited raw header into a Vec.
 #[inline]
-pub fn from_comma_delimited<T: str::FromStr>(raw: &[Vec<u8>]) -> Option<Vec<T>> {
+pub fn from_comma_delimited<T: str::FromStr>(raw: &[Vec<u8>]) -> ::Result<Vec<T>> {
     if raw.len() != 1 {
-        return None;
+        return Err(::Error::Header);
     }
     // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
     from_one_comma_delimited(& unsafe { raw.get_unchecked(0) }[..])
 }
 
 /// Reads a comma-delimited raw string into a Vec.
-pub fn from_one_comma_delimited<T: str::FromStr>(raw: &[u8]) -> Option<Vec<T>> {
-    match str::from_utf8(raw) {
-        Ok(s) => {
-            Some(s
-                 .split(',')
-                 .filter_map(|x| match x.trim() {
-                     "" => None,
-                     y => Some(y)
-                     })
-                 .filter_map(|x| x.parse().ok())
-                 .collect())
-        }
-        Err(_) => None
-    }
+pub fn from_one_comma_delimited<T: str::FromStr>(raw: &[u8]) -> ::Result<Vec<T>> {
+    let s = try!(str::from_utf8(raw));
+    Ok(s.split(',')
+        .filter_map(|x| match x.trim() {
+            "" => None,
+            y => Some(y)
+        })
+        .filter_map(|x| x.parse().ok())
+        .collect())
 }
 
 /// Format an array into a comma-delimited string.