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</pre></div><pre class="rust"><code><span class="kw">use </span>std::fmt;
<span class="kw">use </span>derive_more::{Display, Error};
<span class="kw">const </span>MAX_QUALITY_INT: u16 = <span class="number">1000</span>;
<span class="kw">const </span>MAX_QUALITY_FLOAT: f32 = <span class="number">1.0</span>;
<span class="doccomment">/// 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
</span><span class="attr">#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
</span><span class="kw">pub struct </span>Quality(<span class="kw">pub</span>(<span class="kw">super</span>) u16);
<span class="kw">impl </span>Quality {
<span class="doccomment">/// The maximum quality value, equivalent to `q=1.0`.
</span><span class="kw">pub const </span>MAX: Quality = Quality(MAX_QUALITY_INT);
<span class="doccomment">/// The minimum, non-zero quality value, equivalent to `q=0.001`.
</span><span class="kw">pub const </span>MIN: Quality = Quality(<span class="number">1</span>);
<span class="doccomment">/// The zero quality value, equivalent to `q=0.0`.
</span><span class="kw">pub const </span>ZERO: Quality = Quality(<span class="number">0</span>);
<span class="doccomment">/// 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.
</span><span class="kw">fn </span>from_f32(value: f32) -> <span class="self">Self </span>{
<span class="comment">// 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.
</span><span class="macro">debug_assert!</span>(
(<span class="number">0.0</span>..=MAX_QUALITY_FLOAT).contains(<span class="kw-2">&</span>value),
<span class="string">"q value must be between 0.0 and 1.0"
</span>);
Quality((value * MAX_QUALITY_INT <span class="kw">as </span>f32) <span class="kw">as </span>u16)
}
}
<span class="doccomment">/// The default value is [`Quality::MAX`].
</span><span class="kw">impl </span>Default <span class="kw">for </span>Quality {
<span class="kw">fn </span>default() -> Quality {
Quality::MAX
}
}
<span class="kw">impl </span>fmt::Display <span class="kw">for </span>Quality {
<span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result {
<span class="kw">match </span><span class="self">self</span>.<span class="number">0 </span>{
<span class="number">0 </span>=> f.write_str(<span class="string">"0"</span>),
MAX_QUALITY_INT => f.write_str(<span class="string">"1"</span>),
<span class="comment">// some number in the range 1–999
</span>x => {
f.write_str(<span class="string">"0."</span>)<span class="question-mark">?</span>;
<span class="comment">// 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.
</span><span class="kw">if </span>x < <span class="number">10 </span>{
<span class="comment">// x in is range 1–9
</span>f.write_str(<span class="string">"00"</span>)<span class="question-mark">?</span>;
<span class="comment">// 0 is already handled so it's not possible to have a trailing 0 in this range
// we can just write the integer
</span>itoa_fmt(f, x)
} <span class="kw">else if </span>x < <span class="number">100 </span>{
<span class="comment">// x in is range 10–99
</span>f.write_str(<span class="string">"0"</span>)<span class="question-mark">?</span>;
<span class="kw">if </span>x % <span class="number">10 </span>== <span class="number">0 </span>{
<span class="comment">// trailing 0, divide by 10 and write
</span>itoa_fmt(f, x / <span class="number">10</span>)
} <span class="kw">else </span>{
itoa_fmt(f, x)
}
} <span class="kw">else </span>{
<span class="comment">// x is in range 100–999
</span><span class="kw">if </span>x % <span class="number">100 </span>== <span class="number">0 </span>{
<span class="comment">// two trailing 0s, divide by 100 and write
</span>itoa_fmt(f, x / <span class="number">100</span>)
} <span class="kw">else if </span>x % <span class="number">10 </span>== <span class="number">0 </span>{
<span class="comment">// one trailing 0, divide by 10 and write
</span>itoa_fmt(f, x / <span class="number">10</span>)
} <span class="kw">else </span>{
itoa_fmt(f, x)
}
}
}
}
}
}
<span class="doccomment">/// Write integer to a `fmt::Write`.
</span><span class="kw">pub fn </span>itoa_fmt<W: fmt::Write, V: itoa::Integer>(<span class="kw-2">mut </span>wr: W, value: V) -> fmt::Result {
<span class="kw">let </span><span class="kw-2">mut </span>buf = itoa::Buffer::new();
wr.write_str(buf.format(value))
}
<span class="attr">#[derive(Debug, Clone, Display, Error)]
#[display(fmt = <span class="string">"quality out of bounds"</span>)]
#[non_exhaustive]
</span><span class="kw">pub struct </span>QualityOutOfBounds;
<span class="kw">impl </span>TryFrom<f32> <span class="kw">for </span>Quality {
<span class="kw">type </span>Error = QualityOutOfBounds;
<span class="attr">#[inline]
</span><span class="kw">fn </span>try_from(value: f32) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, <span class="self">Self</span>::Error> {
<span class="kw">if </span>(<span class="number">0.0</span>..=MAX_QUALITY_FLOAT).contains(<span class="kw-2">&</span>value) {
<span class="prelude-val">Ok</span>(Quality::from_f32(value))
} <span class="kw">else </span>{
<span class="prelude-val">Err</span>(QualityOutOfBounds)
}
}
}
<span class="doccomment">/// 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);
/// ```
</span><span class="attr">#[inline]
</span><span class="kw">pub fn </span>q<T>(quality: T) -> Quality
<span class="kw">where
</span>T: TryInto<Quality>,
T::Error: fmt::Debug,
{
quality.try_into().expect(<span class="string">"quality value was out of bounds"</span>)
}
<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>tests {
<span class="kw">use super</span>::<span class="kw-2">*</span>;
<span class="attr">#[test]
</span><span class="kw">fn </span>q_helper() {
<span class="macro">assert_eq!</span>(q(<span class="number">0.5</span>), Quality(<span class="number">500</span>));
}
<span class="attr">#[test]
</span><span class="kw">fn </span>display_output() {
<span class="macro">assert_eq!</span>(Quality::ZERO.to_string(), <span class="string">"0"</span>);
<span class="macro">assert_eq!</span>(Quality::MIN.to_string(), <span class="string">"0.001"</span>);
<span class="macro">assert_eq!</span>(Quality::MAX.to_string(), <span class="string">"1"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.0</span>).to_string(), <span class="string">"0"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">1.0</span>).to_string(), <span class="string">"1"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.001</span>).to_string(), <span class="string">"0.001"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.5</span>).to_string(), <span class="string">"0.5"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.22</span>).to_string(), <span class="string">"0.22"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.123</span>).to_string(), <span class="string">"0.123"</span>);
<span class="macro">assert_eq!</span>(q(<span class="number">0.999</span>).to_string(), <span class="string">"0.999"</span>);
<span class="kw">for </span>x <span class="kw">in </span><span class="number">0</span>..=<span class="number">1000 </span>{
<span class="comment">// if trailing zeroes are handled correctly, we would not expect the serialized length
// to ever exceed "0." + 3 decimal places = 5 in length
</span><span class="macro">assert!</span>(q(x <span class="kw">as </span>f32 / <span class="number">1000.0</span>).to_string().len() <= <span class="number">5</span>);
}
}
<span class="attr">#[test]
#[should_panic]
</span><span class="kw">fn </span>negative_quality() {
q(-<span class="number">1.0</span>);
}
<span class="attr">#[test]
#[should_panic]
</span><span class="kw">fn </span>quality_out_of_bounds() {
q(<span class="number">2.0</span>);
}
}
</code></pre></div></section></main></body></html>