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| </pre><pre class="rust"><code><span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::ops::RangeInclusive; |
| |
| <span class="kw">use </span>fastdivide::DividerU64; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::MonotonicallyMappableToU128; |
| |
| <span class="doccomment">/// Monotonic maps a value to u64 value space. |
| /// Monotonic mapping enables `PartialOrd` on u64 space without conversion to original space. |
| </span><span class="kw">pub trait </span>MonotonicallyMappableToU64: |
| <span class="lifetime">'static </span>+ PartialOrd + Copy + Send + Sync + fmt::Debug |
| { |
| <span class="doccomment">/// Converts a value to u64. |
| /// |
| /// Internally all fast field values are encoded as u64. |
| </span><span class="kw">fn </span>to_u64(<span class="self">self</span>) -> u64; |
| |
| <span class="doccomment">/// Converts a value from u64 |
| /// |
| /// Internally all fast field values are encoded as u64. |
| /// **Note: To be used for converting encoded Term, Posting values.** |
| </span><span class="kw">fn </span>from_u64(val: u64) -> <span class="self">Self</span>; |
| } |
| |
| <span class="doccomment">/// Values need to be strictly monotonic mapped to a `Internal` value (u64 or u128) that can be |
| /// used in fast field codecs. |
| /// |
| /// The monotonic mapping is required so that `PartialOrd` can be used on `Internal` without |
| /// converting to `External`. |
| /// |
| /// All strictly monotonic functions are invertible because they are guaranteed to have a one-to-one |
| /// mapping from their range to their domain. The `inverse` method is required when opening a codec, |
| /// so a value can be converted back to its original domain (e.g. ip address or f64) from its |
| /// internal representation. |
| </span><span class="kw">pub trait </span>StrictlyMonotonicFn<External: Copy, Internal: Copy> { |
| <span class="doccomment">/// Strictly monotonically maps the value from External to Internal. |
| </span><span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, inp: External) -> Internal; |
| <span class="doccomment">/// Inverse of `mapping`. Maps the value from Internal to External. |
| </span><span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, out: Internal) -> External; |
| |
| <span class="doccomment">/// Maps a user provded value from External to Internal. |
| /// It may be necessary to coerce the value if it is outside the value space. |
| /// In that case it tries to find the next greater value in the value space. |
| /// |
| /// Returns a bool to mark if a value was outside the value space and had to be coerced _up_. |
| /// With that information we can detect if two values in a range both map outside the same value |
| /// space. |
| /// |
| /// coerce_up means the next valid upper value in the value space will be chosen if the value |
| /// has to be coerced. |
| </span><span class="kw">fn </span>mapping_coerce(<span class="kw-2">&</span><span class="self">self</span>, inp: RangeInclusive<External>) -> RangeInclusive<Internal> { |
| <span class="self">self</span>.mapping(<span class="kw-2">*</span>inp.start())..=<span class="self">self</span>.mapping(<span class="kw-2">*</span>inp.end()) |
| } |
| <span class="doccomment">/// Inverse of `mapping_coerce`. |
| </span><span class="kw">fn </span>inverse_coerce(<span class="kw-2">&</span><span class="self">self</span>, out: RangeInclusive<Internal>) -> RangeInclusive<External> { |
| <span class="self">self</span>.inverse(<span class="kw-2">*</span>out.start())..=<span class="self">self</span>.inverse(<span class="kw-2">*</span>out.end()) |
| } |
| } |
| |
| <span class="doccomment">/// Inverts a strictly monotonic mapping from `StrictlyMonotonicFn<A, B>` to |
| /// `StrictlyMonotonicFn<B, A>`. |
| /// |
| /// # Warning |
| /// |
| /// This type comes with a footgun. A type being strictly monotonic does not impose that the inverse |
| /// mapping is strictly monotonic over the entire space External. e.g. a -> a * 2. Use at your own |
| /// risks. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>StrictlyMonotonicMappingInverter<T> { |
| orig_mapping: T, |
| } |
| <span class="kw">impl</span><T> From<T> <span class="kw">for </span>StrictlyMonotonicMappingInverter<T> { |
| <span class="kw">fn </span>from(orig_mapping: T) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ orig_mapping } |
| } |
| } |
| |
| <span class="kw">impl</span><From, To, T> StrictlyMonotonicFn<To, From> <span class="kw">for </span>StrictlyMonotonicMappingInverter<T> |
| <span class="kw">where |
| </span>T: StrictlyMonotonicFn<From, To>, |
| From: Copy, |
| To: Copy, |
| { |
| <span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, val: To) -> From { |
| <span class="self">self</span>.orig_mapping.inverse(val) |
| } |
| |
| <span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, val: From) -> To { |
| <span class="self">self</span>.orig_mapping.mapping(val) |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>mapping_coerce(<span class="kw-2">&</span><span class="self">self</span>, inp: RangeInclusive<To>) -> RangeInclusive<From> { |
| <span class="self">self</span>.orig_mapping.inverse_coerce(inp) |
| } |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>inverse_coerce(<span class="kw-2">&</span><span class="self">self</span>, out: RangeInclusive<From>) -> RangeInclusive<To> { |
| <span class="self">self</span>.orig_mapping.mapping_coerce(out) |
| } |
| } |
| |
| <span class="doccomment">/// Applies the strictly monotonic mapping from `T` without any additional changes. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>StrictlyMonotonicMappingToInternal<T> { |
| _phantom: PhantomData<T>, |
| } |
| |
| <span class="kw">impl</span><T> StrictlyMonotonicMappingToInternal<T> { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new() -> StrictlyMonotonicMappingToInternal<T> { |
| <span class="self">Self </span>{ |
| _phantom: PhantomData, |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><External: MonotonicallyMappableToU128, T: MonotonicallyMappableToU128> |
| StrictlyMonotonicFn<External, u128> <span class="kw">for </span>StrictlyMonotonicMappingToInternal<T> |
| <span class="kw">where </span>T: MonotonicallyMappableToU128 |
| { |
| <span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, inp: External) -> u128 { |
| External::to_u128(inp) |
| } |
| |
| <span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, out: u128) -> External { |
| External::from_u128(out) |
| } |
| } |
| |
| <span class="kw">impl</span><External: MonotonicallyMappableToU64, T: MonotonicallyMappableToU64> |
| StrictlyMonotonicFn<External, u64> <span class="kw">for </span>StrictlyMonotonicMappingToInternal<T> |
| <span class="kw">where </span>T: MonotonicallyMappableToU64 |
| { |
| <span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, inp: External) -> u64 { |
| External::to_u64(inp) |
| } |
| |
| <span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, out: u64) -> External { |
| External::from_u64(out) |
| } |
| } |
| |
| <span class="doccomment">/// Mapping dividing by gcd and a base value. |
| /// |
| /// The function is assumed to be only called on values divided by passed |
| /// gcd value. (It is necessary for the function to be monotonic.) |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>StrictlyMonotonicMappingToInternalGCDBaseval { |
| gcd_divider: DividerU64, |
| gcd: u64, |
| min_value: u64, |
| } |
| <span class="kw">impl </span>StrictlyMonotonicMappingToInternalGCDBaseval { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(gcd: u64, min_value: u64) -> <span class="self">Self </span>{ |
| <span class="kw">let </span>gcd_divider = DividerU64::divide_by(gcd); |
| <span class="self">Self </span>{ |
| gcd_divider, |
| gcd, |
| min_value, |
| } |
| } |
| } |
| <span class="kw">impl</span><External: MonotonicallyMappableToU64> StrictlyMonotonicFn<External, u64> |
| <span class="kw">for </span>StrictlyMonotonicMappingToInternalGCDBaseval |
| { |
| <span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, inp: External) -> u64 { |
| <span class="self">self</span>.gcd_divider |
| .divide(External::to_u64(inp) - <span class="self">self</span>.min_value) |
| } |
| |
| <span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, out: u64) -> External { |
| External::from_u64(<span class="self">self</span>.min_value + out * <span class="self">self</span>.gcd) |
| } |
| |
| <span class="attribute">#[inline] |
| #[allow(clippy::reversed_empty_ranges)] |
| </span><span class="kw">fn </span>mapping_coerce(<span class="kw-2">&</span><span class="self">self</span>, inp: RangeInclusive<External>) -> RangeInclusive<u64> { |
| <span class="kw">let </span>end = External::to_u64(<span class="kw-2">*</span>inp.end()); |
| <span class="kw">if </span>end < <span class="self">self</span>.min_value || inp.end() < inp.start() { |
| <span class="kw">return </span><span class="number">1</span>..=<span class="number">0</span>; |
| } |
| <span class="kw">let </span>map_coerce = |<span class="kw-2">mut </span>inp, coerce_up| { |
| <span class="kw">let </span>inp_lower_bound = <span class="self">self</span>.inverse(<span class="number">0</span>); |
| <span class="kw">if </span>inp < inp_lower_bound { |
| inp = inp_lower_bound; |
| } |
| <span class="kw">let </span>val = External::to_u64(inp); |
| <span class="kw">let </span>need_coercion = coerce_up && (val - <span class="self">self</span>.min_value) % <span class="self">self</span>.gcd != <span class="number">0</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>mapped_val = <span class="self">self</span>.mapping(inp); |
| <span class="kw">if </span>need_coercion { |
| mapped_val += <span class="number">1</span>; |
| } |
| mapped_val |
| }; |
| <span class="kw">let </span>start = map_coerce(<span class="kw-2">*</span>inp.start(), <span class="bool-val">true</span>); |
| <span class="kw">let </span>end = map_coerce(<span class="kw-2">*</span>inp.end(), <span class="bool-val">false</span>); |
| start..=end |
| } |
| } |
| |
| <span class="doccomment">/// Strictly monotonic mapping with a base value. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>StrictlyMonotonicMappingToInternalBaseval { |
| min_value: u64, |
| } |
| <span class="kw">impl </span>StrictlyMonotonicMappingToInternalBaseval { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(min_value: u64) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ min_value } |
| } |
| } |
| |
| <span class="kw">impl</span><External: MonotonicallyMappableToU64> StrictlyMonotonicFn<External, u64> |
| <span class="kw">for </span>StrictlyMonotonicMappingToInternalBaseval |
| { |
| <span class="attribute">#[inline] |
| #[allow(clippy::reversed_empty_ranges)] |
| </span><span class="kw">fn </span>mapping_coerce(<span class="kw-2">&</span><span class="self">self</span>, inp: RangeInclusive<External>) -> RangeInclusive<u64> { |
| <span class="kw">if </span>External::to_u64(<span class="kw-2">*</span>inp.end()) < <span class="self">self</span>.min_value { |
| <span class="kw">return </span><span class="number">1</span>..=<span class="number">0</span>; |
| } |
| <span class="kw">let </span>start = <span class="self">self</span>.mapping(External::to_u64(<span class="kw-2">*</span>inp.start()).max(<span class="self">self</span>.min_value)); |
| <span class="kw">let </span>end = <span class="self">self</span>.mapping(External::to_u64(<span class="kw-2">*</span>inp.end())); |
| start..=end |
| } |
| |
| <span class="kw">fn </span>mapping(<span class="kw-2">&</span><span class="self">self</span>, val: External) -> u64 { |
| External::to_u64(val) - <span class="self">self</span>.min_value |
| } |
| |
| <span class="kw">fn </span>inverse(<span class="kw-2">&</span><span class="self">self</span>, val: u64) -> External { |
| External::from_u64(<span class="self">self</span>.min_value + val) |
| } |
| } |
| |
| <span class="kw">impl </span>MonotonicallyMappableToU64 <span class="kw">for </span>u64 { |
| <span class="kw">fn </span>to_u64(<span class="self">self</span>) -> u64 { |
| <span class="self">self |
| </span>} |
| |
| <span class="kw">fn </span>from_u64(val: u64) -> <span class="self">Self </span>{ |
| val |
| } |
| } |
| |
| <span class="kw">impl </span>MonotonicallyMappableToU64 <span class="kw">for </span>i64 { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>to_u64(<span class="self">self</span>) -> u64 { |
| common::i64_to_u64(<span class="self">self</span>) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>from_u64(val: u64) -> <span class="self">Self </span>{ |
| common::u64_to_i64(val) |
| } |
| } |
| |
| <span class="kw">impl </span>MonotonicallyMappableToU64 <span class="kw">for </span>bool { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>to_u64(<span class="self">self</span>) -> u64 { |
| u64::from(<span class="self">self</span>) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>from_u64(val: u64) -> <span class="self">Self </span>{ |
| val > <span class="number">0 |
| </span>} |
| } |
| |
| <span class="kw">impl </span>MonotonicallyMappableToU64 <span class="kw">for </span>f64 { |
| <span class="kw">fn </span>to_u64(<span class="self">self</span>) -> u64 { |
| common::f64_to_u64(<span class="self">self</span>) |
| } |
| |
| <span class="kw">fn </span>from_u64(val: u64) -> <span class="self">Self </span>{ |
| common::u64_to_f64(val) |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>strictly_monotonic_test() { |
| <span class="comment">// identity mapping |
| </span>test_round_trip(<span class="kw-2">&</span>StrictlyMonotonicMappingToInternal::<u64>::new(), <span class="number">100u64</span>); |
| <span class="comment">// round trip to i64 |
| </span>test_round_trip(<span class="kw-2">&</span>StrictlyMonotonicMappingToInternal::<i64>::new(), <span class="number">100u64</span>); |
| <span class="comment">// identity mapping |
| </span>test_round_trip(<span class="kw-2">&</span>StrictlyMonotonicMappingToInternal::<u128>::new(), <span class="number">100u128</span>); |
| |
| <span class="comment">// base value to i64 round trip |
| </span><span class="kw">let </span>mapping = StrictlyMonotonicMappingToInternalBaseval::new(<span class="number">100</span>); |
| test_round_trip::<<span class="kw">_</span>, <span class="kw">_</span>, u64>(<span class="kw-2">&</span>mapping, <span class="number">100i64</span>); |
| <span class="comment">// base value and gcd to u64 round trip |
| </span><span class="kw">let </span>mapping = StrictlyMonotonicMappingToInternalGCDBaseval::new(<span class="number">10</span>, <span class="number">100</span>); |
| test_round_trip::<<span class="kw">_</span>, <span class="kw">_</span>, u64>(<span class="kw-2">&</span>mapping, <span class="number">100u64</span>); |
| } |
| |
| <span class="kw">fn </span>test_round_trip<T: StrictlyMonotonicFn<K, L>, K: std::fmt::Debug + Eq + Copy, L: Copy>( |
| mapping: <span class="kw-2">&</span>T, |
| test_val: K, |
| ) { |
| <span class="macro">assert_eq!</span>(mapping.inverse(mapping.mapping(test_val)), test_val); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="fastfield_codecs" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
