Restructure code base.

src/func/hashing.rs

@@ -0,0 +1,140 @@
+//! Module containing utilities to hash functions and function calls.
+
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+use std::{
+    any::TypeId,
+    hash::{BuildHasher, Hash, Hasher},
+    iter::empty,
+};
+
+/// A hasher that only takes one single [`u64`] and returns it as a hash key.
+///
+/// # Panics
+///
+/// Panics when hashing any data type other than a [`u64`].
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct StraightHasher(u64);
+
+impl Hasher for StraightHasher {
+    #[inline(always)]
+    fn finish(&self) -> u64 {
+        self.0
+    }
+    #[inline]
+    fn write(&mut self, bytes: &[u8]) {
+        assert_eq!(bytes.len(), 8, "StraightHasher can only hash u64 values");
+
+        let mut key = [0_u8; 8];
+        key.copy_from_slice(bytes);
+
+        self.0 = u64::from_ne_bytes(key);
+    }
+}
+
+/// A hash builder for `StraightHasher`.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash, Default)]
+pub struct StraightHasherBuilder;
+
+impl BuildHasher for StraightHasherBuilder {
+    type Hasher = StraightHasher;
+
+    #[inline(always)]
+    fn build_hasher(&self) -> Self::Hasher {
+        StraightHasher(42)
+    }
+}
+
+/// Create an instance of the default hasher.
+#[inline(always)]
+#[must_use]
+pub fn get_hasher() -> ahash::AHasher {
+    Default::default()
+}
+
+/// Calculate a [`u64`] hash key from a namespace-qualified variable name.
+///
+/// Module names are passed in via `&str` references from an iterator.
+/// Parameter types are passed in via [`TypeId`] values from an iterator.
+///
+/// # Note
+///
+/// The first module name is skipped.  Hashing starts from the _second_ module in the chain.
+#[inline]
+#[must_use]
+pub fn calc_qualified_var_hash<'a>(modules: impl Iterator<Item = &'a str>, var_name: &str) -> u64 {
+    let s = &mut get_hasher();
+
+    // We always skip the first module
+    let mut len = 0;
+    modules
+        .inspect(|_| len += 1)
+        .skip(1)
+        .for_each(|m| m.hash(s));
+    len.hash(s);
+    var_name.hash(s);
+    s.finish()
+}
+
+/// Calculate a [`u64`] hash key from a namespace-qualified function name
+/// and the number of parameters, but no parameter types.
+///
+/// Module names are passed in via `&str` references from an iterator.
+/// Parameter types are passed in via [`TypeId`] values from an iterator.
+///
+/// # Note
+///
+/// The first module name is skipped.  Hashing starts from the _second_ module in the chain.
+#[inline]
+#[must_use]
+pub fn calc_qualified_fn_hash<'a>(
+    modules: impl Iterator<Item = &'a str>,
+    fn_name: &str,
+    num: usize,
+) -> u64 {
+    let s = &mut get_hasher();
+
+    // We always skip the first module
+    let mut len = 0;
+    modules
+        .inspect(|_| len += 1)
+        .skip(1)
+        .for_each(|m| m.hash(s));
+    len.hash(s);
+    fn_name.hash(s);
+    num.hash(s);
+    s.finish()
+}
+
+/// Calculate a [`u64`] hash key from a non-namespace-qualified function name
+/// and the number of parameters, but no parameter types.
+///
+/// Parameter types are passed in via [`TypeId`] values from an iterator.
+#[inline(always)]
+#[must_use]
+pub fn calc_fn_hash(fn_name: &str, num: usize) -> u64 {
+    calc_qualified_fn_hash(empty(), fn_name, num)
+}
+
+/// Calculate a [`u64`] hash key from a list of parameter types.
+///
+/// Parameter types are passed in via [`TypeId`] values from an iterator.
+#[inline]
+#[must_use]
+pub fn calc_fn_params_hash(params: impl Iterator<Item = TypeId>) -> u64 {
+    let s = &mut get_hasher();
+    let mut len = 0;
+    params.for_each(|t| {
+        len += 1;
+        t.hash(s);
+    });
+    len.hash(s);
+    s.finish()
+}
+
+/// Combine two [`u64`] hashes by taking the XOR of them.
+#[inline(always)]
+#[must_use]
+pub(crate) const fn combine_hashes(a: u64, b: u64) -> u64 {
+    a ^ b
+}