364 lines
12 KiB
Rust
364 lines
12 KiB
Rust
#[cfg(all(feature = "runtime-rng", not(all(feature = "compile-time-rng", test))))]
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use crate::convert::Convert;
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#[cfg(feature = "specialize")]
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use crate::BuildHasherExt;
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#[cfg(any(
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all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)),
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all(any(target_arch = "arm", target_arch = "aarch64"), target_feature = "crypto", not(miri), feature = "stdsimd")
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))]
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pub use crate::aes_hash::*;
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#[cfg(not(any(
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all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)),
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all(any(target_arch = "arm", target_arch = "aarch64"), target_feature = "crypto", not(miri), feature = "stdsimd")
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)))]
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pub use crate::fallback_hash::*;
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#[cfg(all(feature = "compile-time-rng", any(not(feature = "runtime-rng"), test)))]
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use const_random::const_random;
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use core::any::{Any, TypeId};
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use core::fmt;
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use core::hash::BuildHasher;
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#[cfg(feature = "specialize")]
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use core::hash::Hash;
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use core::hash::Hasher;
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#[cfg(not(feature = "std"))]
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extern crate alloc;
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#[cfg(feature = "std")]
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extern crate std as alloc;
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#[cfg(feature = "atomic-polyfill")]
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use atomic_polyfill as atomic;
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#[cfg(not(feature = "atomic-polyfill"))]
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use core::sync::atomic;
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use alloc::boxed::Box;
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use atomic::{AtomicUsize, Ordering};
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#[cfg(not(all(target_arch = "arm", target_os = "none")))]
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use once_cell::race::OnceBox;
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#[cfg(any(
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all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)),
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all(any(target_arch = "arm", target_arch = "aarch64"), target_feature = "crypto", not(miri), feature = "stdsimd")
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))]
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use crate::aes_hash::*;
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#[cfg(not(any(
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all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)),
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all(any(target_arch = "arm", target_arch = "aarch64"), target_feature = "crypto", not(miri), feature = "stdsimd")
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)))]
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use crate::fallback_hash::*;
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#[cfg(not(all(target_arch = "arm", target_os = "none")))]
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static RAND_SOURCE: OnceBox<Box<dyn RandomSource + Send + Sync>> = OnceBox::new();
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/// A supplier of Randomness used for different hashers.
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/// See [RandomState.set_random_source].
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pub trait RandomSource {
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fn get_fixed_seeds(&self) -> &'static [[u64; 4]; 2];
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fn gen_hasher_seed(&self) -> usize;
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}
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pub(crate) const PI: [u64; 4] = [
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0x243f_6a88_85a3_08d3,
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0x1319_8a2e_0370_7344,
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0xa409_3822_299f_31d0,
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0x082e_fa98_ec4e_6c89,
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];
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pub(crate) const PI2: [u64; 4] = [
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0x4528_21e6_38d0_1377,
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0xbe54_66cf_34e9_0c6c,
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0xc0ac_29b7_c97c_50dd,
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0x3f84_d5b5_b547_0917,
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];
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struct DefaultRandomSource {
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counter: AtomicUsize,
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}
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impl DefaultRandomSource {
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fn new() -> DefaultRandomSource {
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DefaultRandomSource {
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counter: AtomicUsize::new(&PI as *const _ as usize),
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}
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}
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const fn default() -> DefaultRandomSource {
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DefaultRandomSource {
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counter: AtomicUsize::new(PI[3] as usize),
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}
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}
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}
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impl RandomSource for DefaultRandomSource {
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#[cfg(all(feature = "runtime-rng", not(all(feature = "compile-time-rng", test))))]
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fn get_fixed_seeds(&self) -> &'static [[u64; 4]; 2] {
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static SEEDS: OnceBox<[[u64; 4]; 2]> = OnceBox::new();
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SEEDS.get_or_init(|| {
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let mut result: [u8; 64] = [0; 64];
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getrandom::getrandom(&mut result).expect("getrandom::getrandom() failed.");
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Box::new(result.convert())
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})
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}
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#[cfg(all(feature = "compile-time-rng", any(not(feature = "runtime-rng"), test)))]
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fn get_fixed_seeds(&self) -> &'static [[u64; 4]; 2] {
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const RAND: [[u64; 4]; 2] = [
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[
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const_random!(u64),
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const_random!(u64),
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const_random!(u64),
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const_random!(u64),
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], [
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const_random!(u64),
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const_random!(u64),
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const_random!(u64),
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const_random!(u64),
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]
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];
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&RAND
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}
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#[cfg(all(not(feature = "runtime-rng"), not(feature = "compile-time-rng")))]
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fn get_fixed_seeds(&self) -> &'static [[u64; 4]; 2] {
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&[PI, PI2]
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}
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#[cfg(not(all(target_arch = "arm", target_os = "none")))]
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fn gen_hasher_seed(&self) -> usize {
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let stack = self as *const _ as usize;
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self.counter.fetch_add(stack, Ordering::Relaxed)
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}
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#[cfg(all(target_arch = "arm", target_os = "none"))]
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fn gen_hasher_seed(&self) -> usize {
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let stack = self as *const _ as usize;
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let previous = self.counter.load(Ordering::Relaxed);
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let new = previous.wrapping_add(stack);
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self.counter.store(new, Ordering::Relaxed);
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new
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}
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}
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/// Provides a [Hasher] factory. This is typically used (e.g. by [HashMap]) to create
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/// [AHasher]s in order to hash the keys of the map. See `build_hasher` below.
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///
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/// [build_hasher]: ahash::
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/// [Hasher]: std::hash::Hasher
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/// [BuildHasher]: std::hash::BuildHasher
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/// [HashMap]: std::collections::HashMap
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#[derive(Clone)]
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pub struct RandomState {
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pub(crate) k0: u64,
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pub(crate) k1: u64,
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pub(crate) k2: u64,
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pub(crate) k3: u64,
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}
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impl fmt::Debug for RandomState {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.pad("RandomState { .. }")
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}
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}
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impl RandomState {
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/// Provides an optional way to manually supply a source of randomness for Hasher keys.
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///
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/// The provided [RandomSource] will be used to be used as a source of randomness by [RandomState] to generate new states.
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/// If this method is not invoked the standard source of randomness is used as described in the Readme.
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///
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/// The source of randomness can only be set once, and must be set before the first RandomState is created.
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/// If the source has already been specified `Err` is returned with a `bool` indicating if the set failed because
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/// method was previously invoked (true) or if the default source is already being used (false).
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#[cfg(not(all(target_arch = "arm", target_os = "none")))]
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pub fn set_random_source(source: impl RandomSource + Send + Sync + 'static) -> Result<(), bool> {
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RAND_SOURCE.set(Box::new(Box::new(source))).map_err(|s| s.as_ref().type_id() != TypeId::of::<&DefaultRandomSource>())
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}
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#[inline]
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#[cfg(not(all(target_arch = "arm", target_os = "none")))]
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fn get_src() -> &'static dyn RandomSource {
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RAND_SOURCE.get_or_init(|| Box::new(Box::new(DefaultRandomSource::new()))).as_ref()
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}
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#[inline]
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#[cfg(all(target_arch = "arm", target_os = "none"))]
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fn get_src() -> &'static dyn RandomSource {
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static RAND_SOURCE: DefaultRandomSource = DefaultRandomSource::default();
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&RAND_SOURCE
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}
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/// Use randomly generated keys
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#[inline]
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pub fn new() -> RandomState {
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let src = Self::get_src();
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let fixed = src.get_fixed_seeds();
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Self::from_keys(&fixed[0], &fixed[1], src.gen_hasher_seed())
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}
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/// Allows for supplying seeds, but each time it is called the resulting state will be different.
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/// This is done using a static counter, so it can safely be used with a fixed keys.
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#[inline]
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pub fn generate_with(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState {
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let src = Self::get_src();
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let fixed = src.get_fixed_seeds();
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RandomState::from_keys(&fixed[0], &[k0, k1, k2, k3], src.gen_hasher_seed())
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}
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fn from_keys(a: &[u64; 4], b: &[u64; 4], c: usize) -> RandomState {
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let &[k0, k1, k2, k3] = a;
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let mut hasher = AHasher::from_random_state(&RandomState { k0, k1, k2, k3 });
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hasher.write_usize(c);
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let mix = |k: u64| {
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let mut h = hasher.clone();
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h.write_u64(k);
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h.finish()
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};
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RandomState {
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k0: mix(b[0]),
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k1: mix(b[1]),
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k2: mix(b[2]),
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k3: mix(b[3]),
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}
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}
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/// Internal. Used by Default.
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#[inline]
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pub(crate) fn with_fixed_keys() -> RandomState {
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let [k0, k1, k2, k3] = Self::get_src().get_fixed_seeds()[0];
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RandomState { k0, k1, k2, k3 }
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}
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/// Allows for explicitly setting a seed to used.
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///
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/// Note: This method does not require the provided seed to be strong.
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#[inline]
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pub fn with_seed(key: usize) -> RandomState {
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let fixed = Self::get_src().get_fixed_seeds();
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RandomState::from_keys(&fixed[0], &fixed[1], key)
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}
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/// Allows for explicitly setting the seeds to used.
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///
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/// Note: This method is robust against 0s being passed for one or more of the parameters
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/// or the same value being passed for more than one parameter.
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#[inline]
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pub const fn with_seeds(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState {
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RandomState { k0: k0 ^ PI2[0], k1: k1 ^ PI2[1], k2: k2 ^ PI2[2], k3: k3 ^ PI2[3] }
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}
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}
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impl Default for RandomState {
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#[inline]
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fn default() -> Self {
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Self::new()
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}
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}
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impl BuildHasher for RandomState {
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type Hasher = AHasher;
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/// Constructs a new [AHasher] with keys based on this [RandomState] object.
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/// This means that two different [RandomState]s will will generate
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/// [AHasher]s that will return different hashcodes, but [Hasher]s created from the same [BuildHasher]
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/// will generate the same hashes for the same input data.
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///
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/// # Examples
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///
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/// ```
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/// use ahash::{AHasher, RandomState};
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/// use std::hash::{Hasher, BuildHasher};
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///
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/// let build_hasher = RandomState::new();
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/// let mut hasher_1 = build_hasher.build_hasher();
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/// let mut hasher_2 = build_hasher.build_hasher();
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///
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/// hasher_1.write_u32(1234);
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/// hasher_2.write_u32(1234);
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///
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/// assert_eq!(hasher_1.finish(), hasher_2.finish());
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///
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/// let other_build_hasher = RandomState::new();
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/// let mut different_hasher = other_build_hasher.build_hasher();
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/// different_hasher.write_u32(1234);
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/// assert_ne!(different_hasher.finish(), hasher_1.finish());
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/// ```
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/// [Hasher]: std::hash::Hasher
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/// [BuildHasher]: std::hash::BuildHasher
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/// [HashMap]: std::collections::HashMap
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#[inline]
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fn build_hasher(&self) -> AHasher {
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AHasher::from_random_state(self)
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}
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}
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#[cfg(feature = "specialize")]
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impl BuildHasherExt for RandomState {
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#[inline]
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fn hash_as_u64<T: Hash + ?Sized>(&self, value: &T) -> u64 {
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let mut hasher = AHasherU64 {
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buffer: self.k0,
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pad: self.k1,
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};
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value.hash(&mut hasher);
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hasher.finish()
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}
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#[inline]
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fn hash_as_fixed_length<T: Hash + ?Sized>(&self, value: &T) -> u64 {
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let mut hasher = AHasherFixed(self.build_hasher());
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value.hash(&mut hasher);
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hasher.finish()
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}
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#[inline]
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fn hash_as_str<T: Hash + ?Sized>(&self, value: &T) -> u64 {
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let mut hasher = AHasherStr(self.build_hasher());
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value.hash(&mut hasher);
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hasher.finish()
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_unique() {
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let a = RandomState::new();
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let b = RandomState::new();
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assert_ne!(a.build_hasher().finish(), b.build_hasher().finish());
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}
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#[cfg(all(feature = "runtime-rng", not(all(feature = "compile-time-rng", test))))]
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#[test]
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fn test_not_pi() {
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assert_ne!(PI, RandomState::get_src().get_fixed_seeds()[0]);
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}
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#[cfg(all(feature = "compile-time-rng", any(not(feature = "runtime-rng"), test)))]
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#[test]
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fn test_not_pi_const() {
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assert_ne!(PI, RandomState::get_src().get_fixed_seeds()[0]);
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}
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#[cfg(all(not(feature = "runtime-rng"), not(feature = "compile-time-rng")))]
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#[test]
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fn test_pi() {
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assert_eq!(PI, RandomState::get_src().get_fixed_seeds()[0]);
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}
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#[test]
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fn test_with_seeds_const() {
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const _CONST_RANDOM_STATE: RandomState = RandomState::with_seeds(17, 19, 21, 23);
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}
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}
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