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use core::default::Default;
use core::hash::{BuildHasherDefault, Hasher};
use core::mem::size_of;
use core::ops::BitXor;
pub type FxHashBuilder = BuildHasherDefault<FxHasher>;
pub struct FxHasher {
hash: usize,
}
#[cfg(target_pointer_width = "32")]
const K: usize = 0x9e37_79b9;
#[cfg(target_pointer_width = "64")]
const K: usize = 0x517c_c1b7_2722_0a95;
impl Default for FxHasher {
#[inline]
fn default() -> Self {
Self { hash: 0 }
}
}
impl FxHasher {
#[inline]
fn add_to_hash(&mut self, i: usize) {
self.hash = self.hash.rotate_left(5).bitxor(i).wrapping_mul(K);
}
}
impl Hasher for FxHasher {
#[inline]
fn write(&mut self, mut bytes: &[u8]) {
macro_rules! read_bytes {
($ty:ty, $src:expr) => {{
assert!(size_of::<$ty>() <= $src.len());
let mut data: $ty = 0;
unsafe {
$src.as_ptr()
.copy_to_nonoverlapping(&mut data as *mut $ty as *mut u8, size_of::<$ty>());
}
data
}};
}
let mut hash = Self { hash: self.hash };
assert!(size_of::<usize>() <= 8);
while bytes.len() >= size_of::<usize>() {
hash.add_to_hash(read_bytes!(usize, bytes) as usize);
bytes = &bytes[size_of::<usize>()..];
}
if (size_of::<usize>() > 4) && (bytes.len() >= 4) {
hash.add_to_hash(read_bytes!(u32, bytes) as usize);
bytes = &bytes[4..];
}
if (size_of::<usize>() > 2) && bytes.len() >= 2 {
hash.add_to_hash(read_bytes!(u16, bytes) as usize);
bytes = &bytes[2..];
}
if (size_of::<usize>() > 1) && !bytes.is_empty() {
hash.add_to_hash(bytes[0] as usize);
}
self.hash = hash.hash;
}
#[inline]
fn write_u8(&mut self, i: u8) {
self.add_to_hash(i as usize);
}
#[inline]
fn write_u16(&mut self, i: u16) {
self.add_to_hash(i as usize);
}
#[inline]
fn write_u32(&mut self, i: u32) {
self.add_to_hash(i as usize);
}
#[cfg(target_pointer_width = "32")]
#[inline]
#[allow(clippy::cast_possible_truncation)]
fn write_u64(&mut self, i: u64) {
self.add_to_hash(i as usize);
self.add_to_hash((i >> 32) as usize);
}
#[cfg(target_pointer_width = "64")]
#[inline]
#[allow(clippy::cast_possible_truncation)]
fn write_u64(&mut self, i: u64) {
self.add_to_hash(i as usize);
}
#[inline]
fn write_usize(&mut self, i: usize) {
self.add_to_hash(i);
}
#[inline]
fn finish(&self) -> u64 {
self.hash as u64
}
}