9 files changed, 1015 insertions, 0 deletions
diff --git a/third_party/rust/headers/src/util/csv.rs b/third_party/rust/headers/src/util/csv.rs
new file mode 100644
index 0000000000..2d0a8ed68d
--- /dev/null
+++ b/third_party/rust/headers/src/util/csv.rs
@@ -0,0 +1,38 @@
+use std::fmt;
+
+/// Reads a comma-delimited raw header into a Vec.
+pub(crate) fn from_comma_delimited<'i, I, T, E>(values: &mut I) -> Result<E, ::Error>
+where
+    I: Iterator<Item = &'i ::HeaderValue>,
+    T: ::std::str::FromStr,
+    E: ::std::iter::FromIterator<T>,
+{
+    values
+        .flat_map(|value| {
+            value.to_str().into_iter().flat_map(|string| {
+                string
+                    .split(',')
+                    .filter_map(|x| match x.trim() {
+                        "" => None,
+                        y => Some(y),
+                    })
+                    .map(|x| x.parse().map_err(|_| ::Error::invalid()))
+            })
+        })
+        .collect()
+}
+
+/// Format an array into a comma-delimited string.
+pub(crate) fn fmt_comma_delimited<T: fmt::Display>(
+    f: &mut fmt::Formatter,
+    mut iter: impl Iterator<Item = T>,
+) -> fmt::Result {
+    if let Some(part) = iter.next() {
+        fmt::Display::fmt(&part, f)?;
+    }
+    for part in iter {
+        f.write_str(", ")?;
+        fmt::Display::fmt(&part, f)?;
+    }
+    Ok(())
+}
diff --git a/third_party/rust/headers/src/util/entity.rs b/third_party/rust/headers/src/util/entity.rs
new file mode 100644
index 0000000000..c966b6fe96
--- /dev/null
+++ b/third_party/rust/headers/src/util/entity.rs
@@ -0,0 +1,357 @@
+use std::fmt;
+
+use super::{FlatCsv, IterExt};
+use HeaderValue;
+
+/// An entity tag, defined in [RFC7232](https://tools.ietf.org/html/rfc7232#section-2.3)
+///
+/// An entity tag consists of a string enclosed by two literal double quotes.
+/// Preceding the first double quote is an optional weakness indicator,
+/// which always looks like `W/`. Examples for valid tags are `"xyzzy"` and `W/"xyzzy"`.
+///
+/// # ABNF
+///
+/// ```text
+/// entity-tag = [ weak ] opaque-tag
+/// weak       = %x57.2F ; "W/", case-sensitive
+/// opaque-tag = DQUOTE *etagc DQUOTE
+/// etagc      = %x21 / %x23-7E / obs-text
+///            ; VCHAR except double quotes, plus obs-text
+/// ```
+///
+/// # Comparison
+/// To check if two entity tags are equivalent in an application always use the `strong_eq` or
+/// `weak_eq` methods based on the context of the Tag. Only use `==` to check if two tags are
+/// identical.
+///
+/// The example below shows the results for a set of entity-tag pairs and
+/// both the weak and strong comparison function results:
+///
+/// | ETag 1  | ETag 2  | Strong Comparison | Weak Comparison |
+/// |---------|---------|-------------------|-----------------|
+/// | `W/"1"` | `W/"1"` | no match          | match           |
+/// | `W/"1"` | `W/"2"` | no match          | no match        |
+/// | `W/"1"` | `"1"`   | no match          | match           |
+/// | `"1"`   | `"1"`   | match             | match           |
+#[derive(Clone, Eq, PartialEq)]
+pub(crate) struct EntityTag<T = HeaderValue>(T);
+
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) enum EntityTagRange {
+    Any,
+    Tags(FlatCsv),
+}
+
+// ===== impl EntityTag =====
+
+impl<T: AsRef<[u8]>> EntityTag<T> {
+    /// Get the tag.
+    pub(crate) fn tag(&self) -> &[u8] {
+        let bytes = self.0.as_ref();
+        let end = bytes.len() - 1;
+        if bytes[0] == b'W' {
+            // W/"<tag>"
+            &bytes[3..end]
+        } else {
+            // "<tag>"
+            &bytes[1..end]
+        }
+    }
+
+    /// Return if this is a "weak" tag.
+    pub(crate) fn is_weak(&self) -> bool {
+        self.0.as_ref()[0] == b'W'
+    }
+
+    /// For strong comparison two entity-tags are equivalent if both are not weak and their
+    /// opaque-tags match character-by-character.
+    pub(crate) fn strong_eq<R>(&self, other: &EntityTag<R>) -> bool
+    where
+        R: AsRef<[u8]>,
+    {
+        !self.is_weak() && !other.is_weak() && self.tag() == other.tag()
+    }
+
+    /// For weak comparison two entity-tags are equivalent if their
+    /// opaque-tags match character-by-character, regardless of either or
+    /// both being tagged as "weak".
+    pub(crate) fn weak_eq<R>(&self, other: &EntityTag<R>) -> bool
+    where
+        R: AsRef<[u8]>,
+    {
+        self.tag() == other.tag()
+    }
+
+    /// The inverse of `EntityTag.strong_eq()`.
+    #[cfg(test)]
+    pub(crate) fn strong_ne(&self, other: &EntityTag) -> bool {
+        !self.strong_eq(other)
+    }
+
+    /// The inverse of `EntityTag.weak_eq()`.
+    #[cfg(test)]
+    pub(crate) fn weak_ne(&self, other: &EntityTag) -> bool {
+        !self.weak_eq(other)
+    }
+
+    pub(crate) fn parse(src: T) -> Option<Self> {
+        let slice = src.as_ref();
+        let length = slice.len();
+
+        // Early exits if it doesn't terminate in a DQUOTE.
+        if length < 2 || slice[length - 1] != b'"' {
+            return None;
+        }
+
+        let start = match slice[0] {
+            // "<tag>"
+            b'"' => 1,
+            // W/"<tag>"
+            b'W' => {
+                if length >= 4 && slice[1] == b'/' && slice[2] == b'"' {
+                    3
+                } else {
+                    return None;
+                }
+            }
+            _ => return None,
+        };
+
+        if check_slice_validity(&slice[start..length - 1]) {
+            Some(EntityTag(src))
+        } else {
+            None
+        }
+    }
+}
+
+impl EntityTag {
+    /*
+    /// Constructs a new EntityTag.
+    /// # Panics
+    /// If the tag contains invalid characters.
+    pub fn new(weak: bool, tag: String) -> EntityTag {
+        assert!(check_slice_validity(&tag), "Invalid tag: {:?}", tag);
+        EntityTag { weak: weak, tag: tag }
+    }
+
+    /// Constructs a new weak EntityTag.
+    /// # Panics
+    /// If the tag contains invalid characters.
+    pub fn weak(tag: String) -> EntityTag {
+        EntityTag::new(true, tag)
+    }
+
+    /// Constructs a new strong EntityTag.
+    /// # Panics
+    /// If the tag contains invalid characters.
+    pub fn strong(tag: String) -> EntityTag {
+        EntityTag::new(false, tag)
+    }
+    */
+
+    #[cfg(test)]
+    pub fn from_static(bytes: &'static str) -> EntityTag {
+        let val = HeaderValue::from_static(bytes);
+        match EntityTag::from_val(&val) {
+            Some(tag) => tag,
+            None => {
+                panic!("invalid static string for EntityTag: {:?}", bytes);
+            }
+        }
+    }
+
+    pub(crate) fn from_owned(val: HeaderValue) -> Option<EntityTag> {
+        EntityTag::parse(val.as_bytes())?;
+        Some(EntityTag(val))
+    }
+
+    pub(crate) fn from_val(val: &HeaderValue) -> Option<EntityTag> {
+        EntityTag::parse(val.as_bytes()).map(|_entity| {
+            EntityTag(val.clone())
+        })
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for EntityTag<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl super::TryFromValues for EntityTag {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        values
+            .just_one()
+            .and_then(EntityTag::from_val)
+            .ok_or_else(::Error::invalid)
+    }
+}
+
+impl From<EntityTag> for HeaderValue {
+    fn from(tag: EntityTag) -> HeaderValue {
+        tag.0
+    }
+}
+
+impl<'a> From<&'a EntityTag> for HeaderValue {
+    fn from(tag: &'a EntityTag) -> HeaderValue {
+        tag.0.clone()
+    }
+}
+
+/// check that each char in the slice is either:
+/// 1. `%x21`, or
+/// 2. in the range `%x23` to `%x7E`, or
+/// 3. above `%x80`
+fn check_slice_validity(slice: &[u8]) -> bool {
+    slice.iter().all(|&c| {
+        // HeaderValue already validates that this doesnt contain control
+        // characters, so we only need to look for DQUOTE (`"`).
+        //
+        // The debug_assert is just in case we use check_slice_validity in
+        // some new context that didnt come from a HeaderValue.
+        debug_assert!(
+            (c >= b'\x21' && c <= b'\x7e') | (c >= b'\x80'),
+            "EntityTag expects HeaderValue to have check for control characters"
+        );
+        c != b'"'
+    })
+}
+
+// ===== impl EntityTagRange =====
+
+impl EntityTagRange {
+    pub(crate) fn matches_strong(&self, entity: &EntityTag) -> bool {
+        self.matches_if(entity, |a, b| a.strong_eq(b))
+    }
+
+    pub(crate) fn matches_weak(&self, entity: &EntityTag) -> bool {
+        self.matches_if(entity, |a, b| a.weak_eq(b))
+    }
+
+    fn matches_if<F>(&self, entity: &EntityTag, func: F) -> bool
+    where
+        F: Fn(&EntityTag<&str>, &EntityTag) -> bool,
+    {
+        match *self {
+            EntityTagRange::Any => true,
+            EntityTagRange::Tags(ref tags) => {
+                tags.iter()
+                    .flat_map(EntityTag::<&str>::parse)
+                    .any(|tag| func(&tag, entity))
+            },
+        }
+    }
+}
+
+impl super::TryFromValues for EntityTagRange {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        let flat = FlatCsv::try_from_values(values)?;
+        if flat.value == "*" {
+            Ok(EntityTagRange::Any)
+        } else {
+            Ok(EntityTagRange::Tags(flat))
+        }
+    }
+}
+
+impl<'a> From<&'a EntityTagRange> for HeaderValue {
+    fn from(tag: &'a EntityTagRange) -> HeaderValue {
+        match *tag {
+            EntityTagRange::Any => HeaderValue::from_static("*"),
+            EntityTagRange::Tags(ref tags) => tags.into(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn parse(slice: &[u8]) -> Option<EntityTag> {
+        let val = HeaderValue::from_bytes(slice).ok()?;
+        EntityTag::from_val(&val)
+    }
+
+    #[test]
+    fn test_etag_parse_success() {
+        // Expected success
+        let tag = parse(b"\"foobar\"").unwrap();
+        assert!(!tag.is_weak());
+        assert_eq!(tag.tag(), b"foobar");
+
+        let weak = parse(b"W/\"weaktag\"").unwrap();
+        assert!(weak.is_weak());
+        assert_eq!(weak.tag(), b"weaktag");
+    }
+
+    #[test]
+    fn test_etag_parse_failures() {
+        // Expected failures
+        macro_rules! fails {
+            ($slice:expr) => {
+                assert_eq!(parse($slice), None);
+            };
+        }
+
+        fails!(b"no-dquote");
+        fails!(b"w/\"the-first-w-is-case sensitive\"");
+        fails!(b"W/\"");
+        fails!(b"");
+        fails!(b"\"unmatched-dquotes1");
+        fails!(b"unmatched-dquotes2\"");
+        fails!(b"\"inner\"quotes\"");
+    }
+
+    /*
+    #[test]
+    fn test_etag_fmt() {
+        assert_eq!(format!("{}", EntityTag::strong("foobar".to_owned())), "\"foobar\"");
+        assert_eq!(format!("{}", EntityTag::strong("".to_owned())), "\"\"");
+        assert_eq!(format!("{}", EntityTag::weak("weak-etag".to_owned())), "W/\"weak-etag\"");
+        assert_eq!(format!("{}", EntityTag::weak("\u{0065}".to_owned())), "W/\"\x65\"");
+        assert_eq!(format!("{}", EntityTag::weak("".to_owned())), "W/\"\"");
+    }
+    */
+
+    #[test]
+    fn test_cmp() {
+        // | ETag 1  | ETag 2  | Strong Comparison | Weak Comparison |
+        // |---------|---------|-------------------|-----------------|
+        // | `W/"1"` | `W/"1"` | no match          | match           |
+        // | `W/"1"` | `W/"2"` | no match          | no match        |
+        // | `W/"1"` | `"1"`   | no match          | match           |
+        // | `"1"`   | `"1"`   | match             | match           |
+        let mut etag1 = EntityTag::from_static("W/\"1\"");
+        let mut etag2 = etag1.clone();
+        assert!(!etag1.strong_eq(&etag2));
+        assert!(etag1.weak_eq(&etag2));
+        assert!(etag1.strong_ne(&etag2));
+        assert!(!etag1.weak_ne(&etag2));
+
+        etag2 = EntityTag::from_static("W/\"2\"");
+        assert!(!etag1.strong_eq(&etag2));
+        assert!(!etag1.weak_eq(&etag2));
+        assert!(etag1.strong_ne(&etag2));
+        assert!(etag1.weak_ne(&etag2));
+
+        etag2 = EntityTag::from_static("\"1\"");
+        assert!(!etag1.strong_eq(&etag2));
+        assert!(etag1.weak_eq(&etag2));
+        assert!(etag1.strong_ne(&etag2));
+        assert!(!etag1.weak_ne(&etag2));
+
+        etag1 = EntityTag::from_static("\"1\"");
+        assert!(etag1.strong_eq(&etag2));
+        assert!(etag1.weak_eq(&etag2));
+        assert!(!etag1.strong_ne(&etag2));
+        assert!(!etag1.weak_ne(&etag2));
+    }
+}
diff --git a/third_party/rust/headers/src/util/flat_csv.rs b/third_party/rust/headers/src/util/flat_csv.rs
new file mode 100644
index 0000000000..099b034212
--- /dev/null
+++ b/third_party/rust/headers/src/util/flat_csv.rs
@@ -0,0 +1,199 @@
+use std::fmt;
+use std::iter::FromIterator;
+use std::marker::PhantomData;
+
+use bytes::BytesMut;
+use util::TryFromValues;
+use HeaderValue;
+
+// A single `HeaderValue` that can flatten multiple values with commas.
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub(crate) struct FlatCsv<Sep = Comma> {
+    pub(crate) value: HeaderValue,
+    _marker: PhantomData<Sep>,
+}
+
+pub(crate) trait Separator {
+    const BYTE: u8;
+    const CHAR: char;
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub(crate) enum Comma {}
+
+impl Separator for Comma {
+    const BYTE: u8 = b',';
+    const CHAR: char = ',';
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub(crate) enum SemiColon {}
+
+impl Separator for SemiColon {
+    const BYTE: u8 = b';';
+    const CHAR: char = ';';
+}
+
+impl<Sep: Separator> FlatCsv<Sep> {
+    pub(crate) fn iter(&self) -> impl Iterator<Item = &str> {
+        self.value.to_str().ok().into_iter().flat_map(|value_str| {
+            let mut in_quotes = false;
+            value_str
+                .split(move |c| {
+                    if in_quotes {
+                        if c == '"' {
+                            in_quotes = false;
+                        }
+                        false // dont split
+                    } else {
+                        if c == Sep::CHAR {
+                            true // split
+                        } else {
+                            if c == '"' {
+                                in_quotes = true;
+                            }
+                            false // dont split
+                        }
+                    }
+                })
+                .map(|item| item.trim())
+        })
+    }
+}
+
+impl<Sep: Separator> TryFromValues for FlatCsv<Sep> {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        let flat = values.collect();
+        Ok(flat)
+    }
+}
+
+impl<Sep> From<HeaderValue> for FlatCsv<Sep> {
+    fn from(value: HeaderValue) -> Self {
+        FlatCsv {
+            value,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<'a, Sep> From<&'a FlatCsv<Sep>> for HeaderValue {
+    fn from(flat: &'a FlatCsv<Sep>) -> HeaderValue {
+        flat.value.clone()
+    }
+}
+
+impl<Sep> fmt::Debug for FlatCsv<Sep> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(&self.value, f)
+    }
+}
+
+impl<'a, Sep: Separator> FromIterator<&'a HeaderValue> for FlatCsv<Sep> {
+    fn from_iter<I>(iter: I) -> Self
+    where
+        I: IntoIterator<Item = &'a HeaderValue>,
+    {
+        let mut values = iter.into_iter();
+
+        // Common case is there is only 1 value, optimize for that
+        if let (1, Some(1)) = values.size_hint() {
+            return values
+                .next()
+                .expect("size_hint claimed 1 item")
+                .clone()
+                .into();
+        }
+
+        // Otherwise, there are multiple, so this should merge them into 1.
+        let mut buf = values
+            .next()
+            .cloned()
+            .map(|val| BytesMut::from(val.as_bytes()))
+            .unwrap_or_else(|| BytesMut::new());
+
+        for val in values {
+            buf.extend_from_slice(&[Sep::BYTE, b' ']);
+            buf.extend_from_slice(val.as_bytes());
+        }
+
+        let val =
+            HeaderValue::from_maybe_shared(buf.freeze()).expect("comma separated HeaderValues are valid");
+
+        val.into()
+    }
+}
+
+// TODO: would be great if there was a way to de-dupe these with above
+impl<Sep: Separator> FromIterator<HeaderValue> for FlatCsv<Sep> {
+    fn from_iter<I>(iter: I) -> Self
+    where
+        I: IntoIterator<Item = HeaderValue>,
+    {
+        let mut values = iter.into_iter();
+
+        // Common case is there is only 1 value, optimize for that
+        if let (1, Some(1)) = values.size_hint() {
+            return values.next().expect("size_hint claimed 1 item").into();
+        }
+
+        // Otherwise, there are multiple, so this should merge them into 1.
+        let mut buf = values
+            .next()
+            .map(|val| BytesMut::from(val.as_bytes()))
+            .unwrap_or_else(|| BytesMut::new());
+
+        for val in values {
+            buf.extend_from_slice(&[Sep::BYTE, b' ']);
+            buf.extend_from_slice(val.as_bytes());
+        }
+
+        let val =
+            HeaderValue::from_maybe_shared(buf.freeze()).expect("comma separated HeaderValues are valid");
+
+        val.into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn comma() {
+        let val = HeaderValue::from_static("aaa, b; bb, ccc");
+        let csv = FlatCsv::<Comma>::from(val);
+
+        let mut values = csv.iter();
+        assert_eq!(values.next(), Some("aaa"));
+        assert_eq!(values.next(), Some("b; bb"));
+        assert_eq!(values.next(), Some("ccc"));
+        assert_eq!(values.next(), None);
+    }
+
+    #[test]
+    fn semicolon() {
+        let val = HeaderValue::from_static("aaa; b, bb; ccc");
+        let csv = FlatCsv::<SemiColon>::from(val);
+
+        let mut values = csv.iter();
+        assert_eq!(values.next(), Some("aaa"));
+        assert_eq!(values.next(), Some("b, bb"));
+        assert_eq!(values.next(), Some("ccc"));
+        assert_eq!(values.next(), None);
+    }
+
+    #[test]
+    fn quoted_text() {
+        let val = HeaderValue::from_static("foo=\"bar,baz\", sherlock=holmes");
+        let csv = FlatCsv::<Comma>::from(val);
+
+        let mut values = csv.iter();
+        assert_eq!(values.next(), Some("foo=\"bar,baz\""));
+        assert_eq!(values.next(), Some("sherlock=holmes"));
+        assert_eq!(values.next(), None);
+    }
+}
diff --git a/third_party/rust/headers/src/util/fmt.rs b/third_party/rust/headers/src/util/fmt.rs
new file mode 100644
index 0000000000..c535c72925
--- /dev/null
+++ b/third_party/rust/headers/src/util/fmt.rs
@@ -0,0 +1,11 @@
+use std::fmt::Display;
+
+use HeaderValue;
+
+pub(crate) fn fmt<T: Display>(fmt: T) -> HeaderValue {
+    let s = fmt.to_string();
+    match HeaderValue::from_maybe_shared(s) {
+        Ok(val) => val,
+        Err(err) => panic!("illegal HeaderValue; error = {:?}, fmt = \"{}\"", err, fmt),
+    }
+}
diff --git a/third_party/rust/headers/src/util/http_date.rs b/third_party/rust/headers/src/util/http_date.rs
new file mode 100644
index 0000000000..da3f83969d
--- /dev/null
+++ b/third_party/rust/headers/src/util/http_date.rs
@@ -0,0 +1,152 @@
+use std::fmt;
+use std::str::FromStr;
+use std::time::SystemTime;
+
+use bytes::Bytes;
+use http::header::HeaderValue;
+use httpdate;
+
+use super::IterExt;
+
+/// A timestamp with HTTP formatting and parsing
+//   Prior to 1995, there were three different formats commonly used by
+//   servers to communicate timestamps.  For compatibility with old
+//   implementations, all three are defined here.  The preferred format is
+//   a fixed-length and single-zone subset of the date and time
+//   specification used by the Internet Message Format [RFC5322].
+//
+//     HTTP-date    = IMF-fixdate / obs-date
+//
+//   An example of the preferred format is
+//
+//     Sun, 06 Nov 1994 08:49:37 GMT    ; IMF-fixdate
+//
+//   Examples of the two obsolete formats are
+//
+//     Sunday, 06-Nov-94 08:49:37 GMT   ; obsolete RFC 850 format
+//     Sun Nov  6 08:49:37 1994         ; ANSI C's asctime() format
+//
+//   A recipient that parses a timestamp value in an HTTP header field
+//   MUST accept all three HTTP-date formats.  When a sender generates a
+//   header field that contains one or more timestamps defined as
+//   HTTP-date, the sender MUST generate those timestamps in the
+//   IMF-fixdate format.
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct HttpDate(httpdate::HttpDate);
+
+impl HttpDate {
+    pub(crate) fn from_val(val: &HeaderValue) -> Option<Self> {
+        val.to_str().ok()?.parse().ok()
+    }
+}
+
+// TODO: remove this and FromStr?
+#[derive(Debug)]
+pub struct Error(());
+
+impl super::TryFromValues for HttpDate {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        values
+            .just_one()
+            .and_then(HttpDate::from_val)
+            .ok_or_else(::Error::invalid)
+    }
+}
+
+impl From<HttpDate> for HeaderValue {
+    fn from(date: HttpDate) -> HeaderValue {
+        (&date).into()
+    }
+}
+
+impl<'a> From<&'a HttpDate> for HeaderValue {
+    fn from(date: &'a HttpDate) -> HeaderValue {
+        // TODO: could be just BytesMut instead of String
+        let s = date.to_string();
+        let bytes = Bytes::from(s);
+        HeaderValue::from_maybe_shared(bytes).expect("HttpDate always is a valid value")
+    }
+}
+
+impl FromStr for HttpDate {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<HttpDate, Error> {
+        Ok(HttpDate(s.parse().map_err(|_| Error(()))?))
+    }
+}
+
+impl fmt::Debug for HttpDate {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl fmt::Display for HttpDate {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl From<SystemTime> for HttpDate {
+    fn from(sys: SystemTime) -> HttpDate {
+        HttpDate(sys.into())
+    }
+}
+
+impl From<HttpDate> for SystemTime {
+    fn from(date: HttpDate) -> SystemTime {
+        SystemTime::from(date.0)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::HttpDate;
+
+    use std::time::{Duration, UNIX_EPOCH};
+
+    // The old tests had Sunday, but 1994-11-07 is a Monday.
+    // See https://github.com/pyfisch/httpdate/pull/6#issuecomment-846881001
+    fn nov_07() -> HttpDate {
+        HttpDate((UNIX_EPOCH + Duration::new(784198117, 0)).into())
+    }
+
+    #[test]
+    fn test_display_is_imf_fixdate() {
+        assert_eq!("Mon, 07 Nov 1994 08:48:37 GMT", &nov_07().to_string());
+    }
+
+    #[test]
+    fn test_imf_fixdate() {
+        assert_eq!(
+            "Mon, 07 Nov 1994 08:48:37 GMT".parse::<HttpDate>().unwrap(),
+            nov_07()
+        );
+    }
+
+    #[test]
+    fn test_rfc_850() {
+        assert_eq!(
+            "Monday, 07-Nov-94 08:48:37 GMT"
+                .parse::<HttpDate>()
+                .unwrap(),
+            nov_07()
+        );
+    }
+
+    #[test]
+    fn test_asctime() {
+        assert_eq!(
+            "Mon Nov  7 08:48:37 1994".parse::<HttpDate>().unwrap(),
+            nov_07()
+        );
+    }
+
+    #[test]
+    fn test_no_date() {
+        assert!("this-is-no-date".parse::<HttpDate>().is_err());
+    }
+}
diff --git a/third_party/rust/headers/src/util/iter.rs b/third_party/rust/headers/src/util/iter.rs
new file mode 100644
index 0000000000..03ed691ed6
--- /dev/null
+++ b/third_party/rust/headers/src/util/iter.rs
@@ -0,0 +1,11 @@
+pub trait IterExt: Iterator {
+    fn just_one(&mut self) -> Option<Self::Item> {
+        let one = self.next()?;
+        match self.next() {
+            Some(_) => None,
+            None => Some(one),
+        }
+    }
+}
+
+impl<T: Iterator> IterExt for T {}
diff --git a/third_party/rust/headers/src/util/mod.rs b/third_party/rust/headers/src/util/mod.rs
new file mode 100644
index 0000000000..07fddbfb6c
--- /dev/null
+++ b/third_party/rust/headers/src/util/mod.rs
@@ -0,0 +1,87 @@
+use HeaderValue;
+
+//pub use self::charset::Charset;
+//pub use self::encoding::Encoding;
+pub(crate) use self::entity::{EntityTag, EntityTagRange};
+pub(crate) use self::flat_csv::{FlatCsv, SemiColon};
+pub(crate) use self::fmt::fmt;
+pub(crate) use self::http_date::HttpDate;
+pub(crate) use self::iter::IterExt;
+//pub use language_tags::LanguageTag;
+//pub use self::quality_value::{Quality, QualityValue};
+pub(crate) use self::seconds::Seconds;
+pub(crate) use self::value_string::HeaderValueString;
+
+//mod charset;
+pub(crate) mod csv;
+//mod encoding;
+mod entity;
+mod flat_csv;
+mod fmt;
+mod http_date;
+mod iter;
+//mod quality_value;
+mod seconds;
+mod value_string;
+
+macro_rules! error_type {
+    ($name:ident) => {
+        #[doc(hidden)]
+        pub struct $name {
+            _inner: (),
+        }
+
+        impl ::std::fmt::Debug for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                f.debug_struct(stringify!($name)).finish()
+            }
+        }
+
+        impl ::std::fmt::Display for $name {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                f.write_str(stringify!($name))
+            }
+        }
+
+        impl ::std::error::Error for $name {}
+    };
+}
+
+macro_rules! derive_header {
+    ($type:ident(_), name: $name:ident) => {
+        impl crate::Header for $type {
+            fn name() -> &'static ::http::header::HeaderName {
+                &::http::header::$name
+            }
+
+            fn decode<'i, I>(values: &mut I) -> Result<Self, ::Error>
+            where
+                I: Iterator<Item = &'i ::http::header::HeaderValue>,
+            {
+                ::util::TryFromValues::try_from_values(values).map($type)
+            }
+
+            fn encode<E: Extend<::HeaderValue>>(&self, values: &mut E) {
+                values.extend(::std::iter::once((&self.0).into()));
+            }
+        }
+    };
+}
+
+/// A helper trait for use when deriving `Header`.
+pub(crate) trait TryFromValues: Sized {
+    /// Try to convert from the values into an instance of `Self`.
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        Self: Sized,
+        I: Iterator<Item = &'i HeaderValue>;
+}
+
+impl TryFromValues for HeaderValue {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        values.next().cloned().ok_or_else(|| ::Error::invalid())
+    }
+}
diff --git a/third_party/rust/headers/src/util/seconds.rs b/third_party/rust/headers/src/util/seconds.rs
new file mode 100644
index 0000000000..a1a9194b0c
--- /dev/null
+++ b/third_party/rust/headers/src/util/seconds.rs
@@ -0,0 +1,67 @@
+use std::fmt;
+use std::time::Duration;
+
+use util::IterExt;
+use HeaderValue;
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct Seconds(Duration);
+
+impl Seconds {
+    pub(crate) fn from_val(val: &HeaderValue) -> Option<Self> {
+        let secs = val.to_str().ok()?.parse().ok()?;
+
+        Some(Self::from_secs(secs))
+    }
+
+    pub(crate) fn from_secs(secs: u64) -> Self {
+        Self::from(Duration::from_secs(secs))
+    }
+
+    pub(crate) fn as_u64(&self) -> u64 {
+        self.0.as_secs()
+    }
+}
+
+impl super::TryFromValues for Seconds {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        values
+            .just_one()
+            .and_then(Seconds::from_val)
+            .ok_or_else(::Error::invalid)
+    }
+}
+
+impl<'a> From<&'a Seconds> for HeaderValue {
+    fn from(secs: &'a Seconds) -> HeaderValue {
+        secs.0.as_secs().into()
+    }
+}
+
+impl From<Duration> for Seconds {
+    fn from(dur: Duration) -> Seconds {
+        debug_assert!(dur.subsec_nanos() == 0);
+        Seconds(dur)
+    }
+}
+
+impl From<Seconds> for Duration {
+    fn from(secs: Seconds) -> Duration {
+        secs.0
+    }
+}
+
+impl fmt::Debug for Seconds {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}s", self.0.as_secs())
+    }
+}
+
+impl fmt::Display for Seconds {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.0.as_secs(), f)
+    }
+}
diff --git a/third_party/rust/headers/src/util/value_string.rs b/third_party/rust/headers/src/util/value_string.rs
new file mode 100644
index 0000000000..865a3558b9
--- /dev/null
+++ b/third_party/rust/headers/src/util/value_string.rs
@@ -0,0 +1,93 @@
+use std::{
+    fmt,
+    str::{self, FromStr},
+};
+
+use bytes::Bytes;
+use http::header::HeaderValue;
+
+use super::IterExt;
+
+/// A value that is both a valid `HeaderValue` and `String`.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct HeaderValueString {
+    /// Care must be taken to only set this value when it is also
+    /// a valid `String`, since `as_str` will convert to a `&str`
+    /// in an unchecked manner.
+    value: HeaderValue,
+}
+
+impl HeaderValueString {
+    pub(crate) fn from_val(val: &HeaderValue) -> Result<Self, ::Error> {
+        if val.to_str().is_ok() {
+            Ok(HeaderValueString { value: val.clone() })
+        } else {
+            Err(::Error::invalid())
+        }
+    }
+
+    pub(crate) fn from_string(src: String) -> Option<Self> {
+        // A valid `str` (the argument)...
+        let bytes = Bytes::from(src);
+        HeaderValue::from_maybe_shared(bytes)
+            .ok()
+            .map(|value| HeaderValueString { value })
+    }
+
+    pub(crate) fn from_static(src: &'static str) -> HeaderValueString {
+        // A valid `str` (the argument)...
+        HeaderValueString {
+            value: HeaderValue::from_static(src),
+        }
+    }
+
+    pub(crate) fn as_str(&self) -> &str {
+        // HeaderValueString is only created from HeaderValues
+        // that have validated they are also UTF-8 strings.
+        unsafe { str::from_utf8_unchecked(self.value.as_bytes()) }
+    }
+}
+
+impl fmt::Debug for HeaderValueString {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(self.as_str(), f)
+    }
+}
+
+impl fmt::Display for HeaderValueString {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self.as_str(), f)
+    }
+}
+
+impl super::TryFromValues for HeaderValueString {
+    fn try_from_values<'i, I>(values: &mut I) -> Result<Self, ::Error>
+    where
+        I: Iterator<Item = &'i HeaderValue>,
+    {
+        values
+            .just_one()
+            .map(HeaderValueString::from_val)
+            .unwrap_or_else(|| Err(::Error::invalid()))
+    }
+}
+
+impl<'a> From<&'a HeaderValueString> for HeaderValue {
+    fn from(src: &'a HeaderValueString) -> HeaderValue {
+        src.value.clone()
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct FromStrError(());
+
+impl FromStr for HeaderValueString {
+    type Err = FromStrError;
+
+    fn from_str(src: &str) -> Result<Self, Self::Err> {
+        // A valid `str` (the argument)...
+        src.parse()
+            .map(|value| HeaderValueString { value })
+            .map_err(|_| FromStrError(()))
+    }
+}