1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225
use std::{
convert::{TryFrom, TryInto},
fmt,
};
use derive_more::{Display, Error};
const MAX_QUALITY_INT: u16 = 1000;
const MAX_QUALITY_FLOAT: f32 = 1.0;
/// Represents a quality used in q-factor values.
///
/// The default value is equivalent to `q=1.0` (the [max](Self::MAX) value).
///
/// # Implementation notes
/// The quality value is defined as a number between 0.0 and 1.0 with three decimal places.
/// This means there are 1001 possible values. Since floating point numbers are not exact and the
/// smallest floating point data type (`f32`) consumes four bytes, we use an `u16` value to store
/// the quality internally.
///
/// [RFC 7231 §5.3.1] gives more information on quality values in HTTP header fields.
///
/// # Examples
/// ```
/// use actix_http::header::{Quality, q};
/// assert_eq!(q(1.0), Quality::MAX);
///
/// assert_eq!(q(0.42).to_string(), "0.42");
/// assert_eq!(q(1.0).to_string(), "1");
/// assert_eq!(Quality::MIN.to_string(), "0.001");
/// assert_eq!(Quality::ZERO.to_string(), "0");
/// ```
///
/// [RFC 7231 §5.3.1]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.1
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct Quality(pub(super) u16);
impl Quality {
/// The maximum quality value, equivalent to `q=1.0`.
pub const MAX: Quality = Quality(MAX_QUALITY_INT);
/// The minimum, non-zero quality value, equivalent to `q=0.001`.
pub const MIN: Quality = Quality(1);
/// The zero quality value, equivalent to `q=0.0`.
pub const ZERO: Quality = Quality(0);
/// Converts a float in the range 0.0–1.0 to a `Quality`.
///
/// Intentionally private. External uses should rely on the `TryFrom` impl.
///
/// # Panics
/// Panics in debug mode when value is not in the range 0.0 <= n <= 1.0.
fn from_f32(value: f32) -> Self {
// Check that `value` is within range should be done before calling this method.
// Just in case, this debug_assert should catch if we were forgetful.
debug_assert!(
(0.0..=MAX_QUALITY_FLOAT).contains(&value),
"q value must be between 0.0 and 1.0"
);
Quality((value * MAX_QUALITY_INT as f32) as u16)
}
}
/// The default value is [`Quality::MAX`].
impl Default for Quality {
fn default() -> Quality {
Quality::MAX
}
}
impl fmt::Display for Quality {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.0 {
0 => f.write_str("0"),
MAX_QUALITY_INT => f.write_str("1"),
// some number in the range 1–999
x => {
f.write_str("0.")?;
// This implementation avoids string allocation for removing trailing zeroes.
// In benchmarks it is twice as fast as approach using something like
// `format!("{}").trim_end_matches('0')` for non-fast-path quality values.
if x < 10 {
// x in is range 1–9
f.write_str("00")?;
// 0 is already handled so it's not possible to have a trailing 0 in this range
// we can just write the integer
itoa_fmt(f, x)
} else if x < 100 {
// x in is range 10–99
f.write_str("0")?;
if x % 10 == 0 {
// trailing 0, divide by 10 and write
itoa_fmt(f, x / 10)
} else {
itoa_fmt(f, x)
}
} else {
// x is in range 100–999
if x % 100 == 0 {
// two trailing 0s, divide by 100 and write
itoa_fmt(f, x / 100)
} else if x % 10 == 0 {
// one trailing 0, divide by 10 and write
itoa_fmt(f, x / 10)
} else {
itoa_fmt(f, x)
}
}
}
}
}
}
/// Write integer to a `fmt::Write`.
pub fn itoa_fmt<W: fmt::Write, V: itoa::Integer>(mut wr: W, value: V) -> fmt::Result {
let mut buf = itoa::Buffer::new();
wr.write_str(buf.format(value))
}
#[derive(Debug, Clone, Display, Error)]
#[display(fmt = "quality out of bounds")]
#[non_exhaustive]
pub struct QualityOutOfBounds;
impl TryFrom<f32> for Quality {
type Error = QualityOutOfBounds;
#[inline]
fn try_from(value: f32) -> Result<Self, Self::Error> {
if (0.0..=MAX_QUALITY_FLOAT).contains(&value) {
Ok(Quality::from_f32(value))
} else {
Err(QualityOutOfBounds)
}
}
}
/// Convenience function to create a [`Quality`] from an `f32` (0.0–1.0).
///
/// Not recommended for use with user input. Rely on the `TryFrom` impls where possible.
///
/// # Panics
/// Panics if value is out of range.
///
/// # Examples
/// ```
/// # use actix_http::header::{q, Quality};
/// let q1 = q(1.0);
/// assert_eq!(q1, Quality::MAX);
///
/// let q2 = q(0.001);
/// assert_eq!(q2, Quality::MIN);
///
/// let q3 = q(0.0);
/// assert_eq!(q3, Quality::ZERO);
///
/// let q4 = q(0.42);
/// ```
///
/// An out-of-range `f32` quality will panic.
/// ```should_panic
/// # use actix_http::header::q;
/// let _q2 = q(1.42);
/// ```
#[inline]
pub fn q<T>(quality: T) -> Quality
where
T: TryInto<Quality>,
T::Error: fmt::Debug,
{
quality.try_into().expect("quality value was out of bounds")
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn q_helper() {
assert_eq!(q(0.5), Quality(500));
}
#[test]
fn display_output() {
assert_eq!(Quality::ZERO.to_string(), "0");
assert_eq!(Quality::MIN.to_string(), "0.001");
assert_eq!(Quality::MAX.to_string(), "1");
assert_eq!(q(0.0).to_string(), "0");
assert_eq!(q(1.0).to_string(), "1");
assert_eq!(q(0.001).to_string(), "0.001");
assert_eq!(q(0.5).to_string(), "0.5");
assert_eq!(q(0.22).to_string(), "0.22");
assert_eq!(q(0.123).to_string(), "0.123");
assert_eq!(q(0.999).to_string(), "0.999");
for x in 0..=1000 {
// if trailing zeroes are handled correctly, we would not expect the serialized length
// to ever exceed "0." + 3 decimal places = 5 in length
assert!(q(x as f32 / 1000.0).to_string().len() <= 5);
}
}
#[test]
#[should_panic]
fn negative_quality() {
q(-1.0);
}
#[test]
#[should_panic]
fn quality_out_of_bounds() {
q(2.0);
}
}