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|
use core::hash::BuildHasher;
use core::hash::Hash;
use core::hash::Hasher;
#[cfg(not(feature = "std"))]
extern crate alloc;
#[cfg(feature = "std")]
extern crate std as alloc;
#[cfg(feature = "specialize")]
use crate::BuildHasherExt;
#[cfg(feature = "specialize")]
use alloc::string::String;
#[cfg(feature = "specialize")]
use alloc::vec::Vec;
/// Provides a way to get an optimized hasher for a given data type.
/// Rather than using a Hasher generically which can hash any value, this provides a way to get a specialized hash
/// for a specific type. So this may be faster for primitive types.
/// # Example
/// ```
/// use std::hash::BuildHasher;
/// use ahash::RandomState;
/// use ahash::CallHasher;
///
/// let hash_builder = RandomState::new();
/// //...
/// let value: u32 = 17;
/// let hash = u32::get_hash(&value, &hash_builder);
/// ```
/// Note that the type used to invoke `get_hash` must be the same a the type of value passed.
/// For example get a hasher specialized on `[u8]` can invoke:
/// ```
/// /// use std::hash::BuildHasher;
/// # use ahash::RandomState;
/// # use ahash::CallHasher;
/// # let hash_builder = RandomState::new();
/// let bytes: [u8; 4] = [1, 2, 3, 4];
/// let hash = <[u8]>::get_hash(&bytes, &hash_builder);
/// ```
pub trait CallHasher {
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64;
}
#[cfg(not(feature = "specialize"))]
impl<T> CallHasher for T
where
T: Hash + ?Sized,
{
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
let mut hasher = build_hasher.build_hasher();
value.hash(&mut hasher);
hasher.finish()
}
}
#[cfg(feature = "specialize")]
impl<T> CallHasher for T
where
T: Hash + ?Sized,
{
#[inline]
default fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
let mut hasher = build_hasher.build_hasher();
value.hash(&mut hasher);
hasher.finish()
}
}
macro_rules! call_hasher_impl {
($typ:ty) => {
#[cfg(feature = "specialize")]
impl CallHasher for $typ {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_u64(value)
}
}
};
}
call_hasher_impl!(u8);
call_hasher_impl!(u16);
call_hasher_impl!(u32);
call_hasher_impl!(u64);
call_hasher_impl!(i8);
call_hasher_impl!(i16);
call_hasher_impl!(i32);
call_hasher_impl!(i64);
#[cfg(feature = "specialize")]
impl CallHasher for u128 {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_fixed_length(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for i128 {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_fixed_length(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for usize {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_fixed_length(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for isize {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_fixed_length(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for [u8] {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_str(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for Vec<u8> {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_str(value)
}
}
#[cfg(feature = "specialize")]
impl CallHasher for str {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_str(value)
}
}
#[cfg(all(feature = "specialize"))]
impl CallHasher for String {
#[inline]
fn get_hash<H: Hash + ?Sized, B: BuildHasher>(value: &H, build_hasher: &B) -> u64 {
build_hasher.hash_as_str(value)
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::*;
#[test]
#[cfg(feature = "specialize")]
pub fn test_specialized_invoked() {
let build_hasher = RandomState::with_seeds(1, 2, 3, 4);
let shortened = u64::get_hash(&0, &build_hasher);
let mut hasher = AHasher::new_with_keys(1, 2);
0_u64.hash(&mut hasher);
assert_ne!(hasher.finish(), shortened);
}
/// Tests that some non-trivial transformation takes place.
#[test]
pub fn test_input_processed() {
let build_hasher = RandomState::with_seeds(2, 2, 2, 2);
assert_ne!(0, u64::get_hash(&0, &build_hasher));
assert_ne!(1, u64::get_hash(&0, &build_hasher));
assert_ne!(2, u64::get_hash(&0, &build_hasher));
assert_ne!(3, u64::get_hash(&0, &build_hasher));
assert_ne!(4, u64::get_hash(&0, &build_hasher));
assert_ne!(5, u64::get_hash(&0, &build_hasher));
assert_ne!(0, u64::get_hash(&1, &build_hasher));
assert_ne!(1, u64::get_hash(&1, &build_hasher));
assert_ne!(2, u64::get_hash(&1, &build_hasher));
assert_ne!(3, u64::get_hash(&1, &build_hasher));
assert_ne!(4, u64::get_hash(&1, &build_hasher));
assert_ne!(5, u64::get_hash(&1, &build_hasher));
let xored = u64::get_hash(&0, &build_hasher) ^ u64::get_hash(&1, &build_hasher);
assert_ne!(0, xored);
assert_ne!(1, xored);
assert_ne!(2, xored);
assert_ne!(3, xored);
assert_ne!(4, xored);
assert_ne!(5, xored);
}
#[test]
pub fn test_ref_independent() {
let build_hasher = RandomState::with_seeds(1, 2, 3, 4);
assert_eq!(u8::get_hash(&&1, &build_hasher), u8::get_hash(&1, &build_hasher));
assert_eq!(u16::get_hash(&&2, &build_hasher), u16::get_hash(&2, &build_hasher));
assert_eq!(u32::get_hash(&&3, &build_hasher), u32::get_hash(&3, &build_hasher));
assert_eq!(u64::get_hash(&&4, &build_hasher), u64::get_hash(&4, &build_hasher));
assert_eq!(u128::get_hash(&&5, &build_hasher), u128::get_hash(&5, &build_hasher));
assert_eq!(
str::get_hash(&"test", &build_hasher),
str::get_hash("test", &build_hasher)
);
assert_eq!(
str::get_hash(&"test", &build_hasher),
String::get_hash(&"test".to_string(), &build_hasher)
);
#[cfg(feature = "specialize")]
assert_eq!(
str::get_hash(&"test", &build_hasher),
<[u8]>::get_hash("test".as_bytes(), &build_hasher)
);
let build_hasher = RandomState::with_seeds(10, 20, 30, 40);
assert_eq!(u8::get_hash(&&&1, &build_hasher), u8::get_hash(&1, &build_hasher));
assert_eq!(u16::get_hash(&&&2, &build_hasher), u16::get_hash(&2, &build_hasher));
assert_eq!(u32::get_hash(&&&3, &build_hasher), u32::get_hash(&3, &build_hasher));
assert_eq!(u64::get_hash(&&&4, &build_hasher), u64::get_hash(&4, &build_hasher));
assert_eq!(u128::get_hash(&&&5, &build_hasher), u128::get_hash(&5, &build_hasher));
assert_eq!(
str::get_hash(&&"test", &build_hasher),
str::get_hash("test", &build_hasher)
);
assert_eq!(
str::get_hash(&&"test", &build_hasher),
String::get_hash(&"test".to_string(), &build_hasher)
);
#[cfg(feature = "specialize")]
assert_eq!(
str::get_hash(&&"test", &build_hasher),
<[u8]>::get_hash(&"test".to_string().into_bytes(), &build_hasher)
);
}
}
|
