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use http::header::{HeaderMap, ACCEPT_ENCODING};
use super::error::FeatureError;
/// Represents a supported content encoding.
#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
pub enum ContentEncoding {
/// A format using the Brotli algorithm.
Br,
/// A format using the zlib structure with deflate algorithm.
Deflate,
/// Gzip algorithm.
Gzip,
/// Indicates no operation is done with encoding.
#[default]
NoOp,
}
impl ContentEncoding {
pub fn from_headers(headers: &HeaderMap) -> Self {
let mut prefer = ContentEncodingWithQValue::default();
for encoding in Self::_from_headers(headers) {
prefer.try_update(encoding);
}
prefer.enc
}
fn _from_headers(headers: &HeaderMap) -> impl Iterator<Item = ContentEncodingWithQValue> + '_ {
headers
.get_all(ACCEPT_ENCODING)
.iter()
.filter_map(|hval| hval.to_str().ok())
.flat_map(|s| s.split(','))
.filter_map(|v| {
let mut v = v.splitn(2, ';');
Self::try_parse(v.next().unwrap().trim()).ok().map(|enc| {
let val = v
.next()
.and_then(|v| QValue::parse(v.trim()))
.unwrap_or_else(QValue::one);
ContentEncodingWithQValue { enc, val }
})
})
}
pub(super) fn try_parse(s: &str) -> Result<Self, FeatureError> {
if s.eq_ignore_ascii_case("gzip") {
Ok(Self::Gzip)
} else if s.eq_ignore_ascii_case("deflate") {
Ok(Self::Deflate)
} else if s.eq_ignore_ascii_case("br") {
Ok(Self::Br)
} else if s.eq_ignore_ascii_case("identity") {
Ok(Self::NoOp)
} else {
Err(FeatureError::Unknown(s.to_string().into_boxed_str()))
}
}
}
struct ContentEncodingWithQValue {
enc: ContentEncoding,
val: QValue,
}
impl Default for ContentEncodingWithQValue {
fn default() -> Self {
Self {
enc: ContentEncoding::NoOp,
val: QValue::zero(),
}
}
}
impl ContentEncodingWithQValue {
fn try_update(&mut self, other: Self) {
if other.val > self.val {
match other.enc {
#[cfg(not(feature = "br"))]
ContentEncoding::Br => return,
#[cfg(not(feature = "de"))]
ContentEncoding::Deflate => return,
#[cfg(not(feature = "gz"))]
ContentEncoding::Gzip => return,
_ => {}
};
*self = other;
}
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
struct QValue(u16);
impl QValue {
const fn zero() -> Self {
Self(0)
}
const fn one() -> Self {
Self(1000)
}
// Parse a q-value as specified in RFC 7231 section 5.3.1.
fn parse(s: &str) -> Option<Self> {
let mut c = s.chars();
// Parse "q=" (case-insensitively).
match c.next() {
Some('q') | Some('Q') => (),
_ => return None,
};
match c.next() {
Some('=') => (),
_ => return None,
};
// Parse leading digit. Since valid q-values are between 0.000 and 1.000, only "0" and "1"
// are allowed.
let mut value = match c.next() {
Some('0') => 0,
Some('1') => 1000,
_ => return None,
};
// Parse optional decimal point.
match c.next() {
Some('.') => (),
None => return Some(Self(value)),
_ => return None,
};
// Parse optional fractional digits. The value of each digit is multiplied by `factor`.
// Since the q-value is represented as an integer between 0 and 1000, `factor` is `100` for
// the first digit, `10` for the next, and `1` for the digit after that.
let mut factor = 100;
loop {
match c.next() {
Some(n @ '0'..='9') => {
// If `factor` is less than `1`, three digits have already been parsed. A
// q-value having more than 3 fractional digits is invalid.
if factor < 1 {
return None;
}
// Add the digit's value multiplied by `factor` to `value`.
value += factor * (n as u16 - '0' as u16);
}
None => {
// No more characters to parse. Check that the value representing the q-value is
// in the valid range.
return if value <= 1000 { Some(Self(value)) } else { None };
}
_ => return None,
};
factor /= 10;
}
}
}