146 lines
3.9 KiB
Rust
146 lines
3.9 KiB
Rust
//! Module containing utilities to hash functions and function calls.
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use crate::config;
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#[cfg(feature = "no_std")]
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use std::prelude::v1::*;
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use std::{
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any::TypeId,
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hash::{BuildHasher, Hash, Hasher},
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};
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#[cfg(feature = "no_std")]
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pub type StraightHashMap<V> = hashbrown::HashMap<u64, V, StraightHasherBuilder>;
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#[cfg(not(feature = "no_std"))]
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pub type StraightHashMap<V> = std::collections::HashMap<u64, V, StraightHasherBuilder>;
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/// A hasher that only takes one single [`u64`] and returns it as a hash key.
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///
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/// # Panics
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///
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/// Panics when hashing any data type other than a [`u64`].
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#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
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pub struct StraightHasher(u64);
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impl Hasher for StraightHasher {
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#[inline(always)]
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#[must_use]
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fn finish(&self) -> u64 {
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self.0
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}
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#[cold]
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#[inline(never)]
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fn write(&mut self, _bytes: &[u8]) {
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panic!("StraightHasher can only hash u64 values");
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}
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#[inline(always)]
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fn write_u64(&mut self, i: u64) {
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self.0 = i;
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}
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}
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/// A hash builder for `StraightHasher`.
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#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash, Default)]
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pub struct StraightHasherBuilder;
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impl BuildHasher for StraightHasherBuilder {
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type Hasher = StraightHasher;
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#[inline(always)]
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#[must_use]
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fn build_hasher(&self) -> Self::Hasher {
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StraightHasher(0)
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}
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}
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/// Create an instance of the default hasher.
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#[inline(always)]
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#[must_use]
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pub fn get_hasher() -> ahash::AHasher {
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match config::hashing::get_ahash_seed() {
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Some([seed1, seed2, seed3, seed4]) if (seed1 | seed2 | seed3 | seed4) != 0 => {
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ahash::RandomState::with_seeds(*seed1, *seed2, *seed3, *seed4).build_hasher()
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}
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_ => ahash::AHasher::default(),
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}
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}
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/// Calculate a [`u64`] hash key from a namespace-qualified variable name.
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///
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/// Module names are passed in via `&str` references from an iterator.
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/// Parameter types are passed in via [`TypeId`] values from an iterator.
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///
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/// # Note
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///
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/// The first module name is skipped. Hashing starts from the _second_ module in the chain.
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#[inline]
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#[must_use]
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pub fn calc_var_hash<'a>(namespace: impl IntoIterator<Item = &'a str>, var_name: &str) -> u64 {
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let s = &mut get_hasher();
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let mut count = 0;
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// We always skip the first module
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namespace.into_iter().for_each(|m| {
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// We always skip the first module
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if count > 0 {
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m.hash(s);
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}
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count += 1;
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});
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s.write_usize(count);
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var_name.hash(s);
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s.finish()
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}
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/// Calculate a [`u64`] hash key from a namespace-qualified function name
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/// and the number of parameters, but no parameter types.
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///
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/// Module names making up the namespace are passed in via `&str` references from an iterator.
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/// Parameter types are passed in via [`TypeId`] values from an iterator.
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///
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/// If the function is not namespace-qualified, pass [`None`] as the namespace.
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///
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/// # Note
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///
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/// The first module name is skipped. Hashing starts from the _second_ module in the chain.
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#[inline]
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#[must_use]
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pub fn calc_fn_hash<'a>(
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namespace: impl IntoIterator<Item = &'a str>,
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fn_name: &str,
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num: usize,
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) -> u64 {
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let s = &mut get_hasher();
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let mut count = 0;
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namespace.into_iter().for_each(|m| {
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// We always skip the first module
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if count > 0 {
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m.hash(s);
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}
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count += 1;
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});
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s.write_usize(count);
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fn_name.hash(s);
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s.write_usize(num);
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s.finish()
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}
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/// Calculate a [`u64`] hash key from a base [`u64`] hash key and a list of parameter types.
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///
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/// Parameter types are passed in via [`TypeId`] values from an iterator.
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#[inline]
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#[must_use]
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pub fn calc_fn_hash_full(base: u64, params: impl IntoIterator<Item = TypeId>) -> u64 {
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let s = &mut get_hasher();
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let mut count = 0;
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params.into_iter().for_each(|t| {
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t.hash(s);
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count += 1;
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});
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s.write_usize(count);
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s.finish() ^ base
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}
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