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use std::{
fmt::{self, Display, Write},
str::FromStr,
};
use super::{HeaderValue, InvalidHeaderValue, TryIntoHeaderValue, Writer};
/// check that each char in the slice is either:
/// 1. `%x21`, or
/// 2. in the range `%x23` to `%x7E`, or
/// 3. above `%x80`
fn entity_validate_char(c: u8) -> bool {
c == 0x21 || (0x23..=0x7e).contains(&c) || (c >= 0x80)
}
fn check_slice_validity(slice: &str) -> bool {
slice.bytes().all(entity_validate_char)
}
/// An entity tag, defined in [RFC 7232 §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
/// ```plain
/// 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 |
///
/// [RFC 7232 §2.3](https://datatracker.ietf.org/doc/html/rfc7232#section-2.3)
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct EntityTag {
/// Weakness indicator for the tag
pub weak: bool,
/// The opaque string in between the DQUOTEs
tag: String,
}
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, tag }
}
/// Constructs a new weak EntityTag.
///
/// # Panics
/// If the tag contains invalid characters.
pub fn new_weak(tag: String) -> EntityTag {
EntityTag::new(true, tag)
}
#[deprecated(since = "3.0.0", note = "Renamed to `new_weak`.")]
pub fn weak(tag: String) -> EntityTag {
Self::new_weak(tag)
}
/// Constructs a new strong EntityTag.
///
/// # Panics
/// If the tag contains invalid characters.
pub fn new_strong(tag: String) -> EntityTag {
EntityTag::new(false, tag)
}
#[deprecated(since = "3.0.0", note = "Renamed to `new_strong`.")]
pub fn strong(tag: String) -> EntityTag {
Self::new_strong(tag)
}
/// Returns tag.
pub fn tag(&self) -> &str {
self.tag.as_ref()
}
/// Sets tag.
///
/// # Panics
/// If the tag contains invalid characters.
pub fn set_tag(&mut self, tag: impl Into<String>) {
let tag = tag.into();
assert!(check_slice_validity(&tag), "Invalid tag: {:?}", tag);
self.tag = tag
}
/// For strong comparison two entity-tags are equivalent if both are not weak and their
/// opaque-tags match character-by-character.
pub fn strong_eq(&self, other: &EntityTag) -> bool {
!self.weak && !other.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 fn weak_eq(&self, other: &EntityTag) -> bool {
self.tag == other.tag
}
/// Returns the inverse of `strong_eq()`.
pub fn strong_ne(&self, other: &EntityTag) -> bool {
!self.strong_eq(other)
}
/// Returns inverse of `weak_eq()`.
pub fn weak_ne(&self, other: &EntityTag) -> bool {
!self.weak_eq(other)
}
}
impl Display for EntityTag {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if self.weak {
write!(f, "W/\"{}\"", self.tag)
} else {
write!(f, "\"{}\"", self.tag)
}
}
}
impl FromStr for EntityTag {
type Err = crate::error::ParseError;
fn from_str(slice: &str) -> Result<EntityTag, crate::error::ParseError> {
let length = slice.len();
// Early exits if it doesn't terminate in a DQUOTE.
if !slice.ends_with('"') || slice.len() < 2 {
return Err(crate::error::ParseError::Header);
}
// The etag is weak if its first char is not a DQUOTE.
if slice.len() >= 2 && slice.starts_with('"') && check_slice_validity(&slice[1..length - 1])
{
// No need to check if the last char is a DQUOTE,
// we already did that above.
return Ok(EntityTag {
weak: false,
tag: slice[1..length - 1].to_owned(),
});
} else if slice.len() >= 4
&& slice.starts_with("W/\"")
&& check_slice_validity(&slice[3..length - 1])
{
return Ok(EntityTag {
weak: true,
tag: slice[3..length - 1].to_owned(),
});
}
Err(crate::error::ParseError::Header)
}
}
impl TryIntoHeaderValue for EntityTag {
type Error = InvalidHeaderValue;
fn try_into_value(self) -> Result<HeaderValue, Self::Error> {
let mut wrt = Writer::new();
write!(wrt, "{}", self).unwrap();
HeaderValue::from_maybe_shared(wrt.take())
}
}
#[cfg(test)]
mod tests {
use super::EntityTag;
#[test]
fn test_etag_parse_success() {
// Expected success
assert_eq!(
"\"foobar\"".parse::<EntityTag>().unwrap(),
EntityTag::new_strong("foobar".to_owned())
);
assert_eq!(
"\"\"".parse::<EntityTag>().unwrap(),
EntityTag::new_strong("".to_owned())
);
assert_eq!(
"W/\"weaktag\"".parse::<EntityTag>().unwrap(),
EntityTag::new_weak("weaktag".to_owned())
);
assert_eq!(
"W/\"\x65\x62\"".parse::<EntityTag>().unwrap(),
EntityTag::new_weak("\x65\x62".to_owned())
);
assert_eq!(
"W/\"\"".parse::<EntityTag>().unwrap(),
EntityTag::new_weak("".to_owned())
);
}
#[test]
fn test_etag_parse_failures() {
// Expected failures
assert!("no-dquotes".parse::<EntityTag>().is_err());
assert!("w/\"the-first-w-is-case-sensitive\""
.parse::<EntityTag>()
.is_err());
assert!("".parse::<EntityTag>().is_err());
assert!("\"unmatched-dquotes1".parse::<EntityTag>().is_err());
assert!("unmatched-dquotes2\"".parse::<EntityTag>().is_err());
assert!("matched-\"dquotes\"".parse::<EntityTag>().is_err());
}
#[test]
fn test_etag_fmt() {
assert_eq!(
format!("{}", EntityTag::new_strong("foobar".to_owned())),
"\"foobar\""
);
assert_eq!(format!("{}", EntityTag::new_strong("".to_owned())), "\"\"");
assert_eq!(
format!("{}", EntityTag::new_weak("weak-etag".to_owned())),
"W/\"weak-etag\""
);
assert_eq!(
format!("{}", EntityTag::new_weak("\u{0065}".to_owned())),
"W/\"\x65\""
);
assert_eq!(format!("{}", EntityTag::new_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::new_weak("1".to_owned());
let mut etag2 = EntityTag::new_weak("1".to_owned());
assert!(!etag1.strong_eq(&etag2));
assert!(etag1.weak_eq(&etag2));
assert!(etag1.strong_ne(&etag2));
assert!(!etag1.weak_ne(&etag2));
etag1 = EntityTag::new_weak("1".to_owned());
etag2 = EntityTag::new_weak("2".to_owned());
assert!(!etag1.strong_eq(&etag2));
assert!(!etag1.weak_eq(&etag2));
assert!(etag1.strong_ne(&etag2));
assert!(etag1.weak_ne(&etag2));
etag1 = EntityTag::new_weak("1".to_owned());
etag2 = EntityTag::new_strong("1".to_owned());
assert!(!etag1.strong_eq(&etag2));
assert!(etag1.weak_eq(&etag2));
assert!(etag1.strong_ne(&etag2));
assert!(!etag1.weak_ne(&etag2));
etag1 = EntityTag::new_strong("1".to_owned());
etag2 = EntityTag::new_strong("1".to_owned());
assert!(etag1.strong_eq(&etag2));
assert!(etag1.weak_eq(&etag2));
assert!(!etag1.strong_ne(&etag2));
assert!(!etag1.weak_ne(&etag2));
}
}