#![allow(clippy::undocumented_unsafe_blocks)]
use core::intrinsics::simd::simd_cast;
#[cfg(all(target_feature = "avx2", not(miri)))]
use std::arch::x86_64::*;
use std::{
intrinsics::transmute_unchecked,
simd::{prelude::*, LaneCount, MaskElement, SimdElement, SupportedLaneCount},
};
#[test]
fn b64() {
fn t(i: &'static str, o: &'static str) {
let mut x = Vec::with_capacity(size(i.as_bytes()));
unsafe { portable(i.as_bytes(), x.as_mut_ptr()) };
unsafe { x.set_len(size(i.as_bytes())) };
assert_eq!(x, o.as_bytes());
}
t("Hello World!", "SGVsbG8gV29ybGQh");
t("Hello World", "SGVsbG8gV29ybGQ=");
}
pub fn encode(i: &[u8]) -> String {
let mut x = Vec::with_capacity(size(i));
unsafe { portable(i, x.as_mut_ptr()) };
unsafe { x.set_len(size(i)) };
unsafe { String::from_utf8_unchecked(x) }
}
trait Cast<T, const N: usize> {
fn cas<U: SimdT>(self) -> U;
}
trait SimdT {}
impl<T: SimdElement, const N: usize> SimdT for Simd<T, N> where LaneCount<N>: SupportedLaneCount {}
impl<T: MaskElement, const N: usize> SimdT for Mask<T, N> where LaneCount<N>: SupportedLaneCount {}
impl<T: SimdElement, const N: usize> Cast<T, N> for Simd<T, N>
where
LaneCount<N>: SupportedLaneCount,
{
fn cas<U>(self) -> U {
assert!(std::mem::size_of::<U>() == std::mem::size_of::<Self>());
unsafe { transmute_unchecked(self) }
}
}
impl<T: MaskElement, const N: usize> Cast<T, N> for Mask<T, N>
where
LaneCount<N>: SupportedLaneCount,
{
fn cas<U>(self) -> U {
assert!(std::mem::size_of::<U>() == std::mem::size_of::<Self>());
unsafe { transmute_unchecked(self) }
}
}
#[allow(non_camel_case_types)]
type c = u8x32;
unsafe fn portable(mut input: &[u8], mut output: *mut u8) {
while input.len() >= 32 {
#[allow(unsafe_op_in_unsafe_fn)]
#[cfg(all(target_feature = "avx2", not(miri)))]
let indices = {
let lo = _mm_loadu_si128(input.as_ptr() as *const __m128i);
let hi = _mm_loadu_si128(input.as_ptr().add(12) as *const __m128i);
let i = _mm256_shuffle_epi8(
_mm256_set_m128i(hi, lo),
_mm256_set_epi8(
10, 11, 9, 10, 7, 8, 6, 7, 4, 5, 3, 4, 1, 2, 0, 1, //
10, 11, 9, 10, 7, 8, 6, 7, 4, 5, 3, 4, 1, 2, 0, 1, //
),
);
let t0 = _mm256_and_si256(i, _mm256_set1_epi32(0x0fc0fc00));
let t1 = _mm256_mulhi_epu16(t0, _mm256_set1_epi32(0x04000040));
let t2 = _mm256_and_si256(i, _mm256_set1_epi32(0x003f03f0));
let t3 = _mm256_mullo_epi16(t2, _mm256_set1_epi32(0x01000010));
c::from(_mm256_or_si256(t1, t3))
};
#[cfg(not(all(target_feature = "avx2", not(miri))))]
let indices = {
let v = c::from_slice(input);
let i = simd_swizzle!(
v,
[
1, 0, 2, 1, 4, 3, 5, 4, 7, 6, 8, 7, 10, 9, 11, 10, 13, 12, //
14, 13, 16, 15, 17, 16, 19, 18, 20, 19, 22, 21, 23, 22
]
);
// https://github.com/WojciechMula/base64simd
let t0 = i & u32x8::splat(0x0fc0fc00).cas::<c>();
let t1 = Cast::cas::<c>(mulhi(t0.cas(), u32x8::splat(0x04000040).cas()));
let t2 = i & u32x8::splat(0x003f03f0).cas::<c>();
let t3 = mullo(t2.cas(), u32x8::splat(0x01000010).cas()).cas::<c>();
t1 | t3
};
lookup(indices).copy_to_slice(unsafe { std::slice::from_raw_parts_mut(output, 32) });
output = unsafe { output.add(32) };
input = &input[24..];
}
unsafe { encode_simple(input, output) };
}
fn mulhi(x: u16x16, y: u16x16) -> u16x16 {
unsafe {
simd_cast::<_, u16x16>(
simd_cast::<_, u32x16>(x) * simd_cast::<_, u32x16>(y) >> u32x16::splat(16),
)
}
}
fn mullo(x: u16x16, y: u16x16) -> u16x16 {
x * y
}
fn lookup(x: c) -> c {
let result = x.saturating_sub(c::splat(51));
let less = cmpgt(c::splat(26), x);
let result = result | (less & c::splat(13));
#[rustfmt::skip]
const LUT: i8x32 = i8x32::from_array([
b'a' as i8 - 26, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52,
b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'+' as i8 - 62,
b'/' as i8 - 63, b'A' as i8, 0, 0,
b'a' as i8 - 26, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52,
b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'0' as i8 - 52, b'+' as i8 - 62,
b'/' as i8 - 63, b'A' as i8, 0, 0
]);
#[cfg(all(target_feature = "avx2", not(miri)))]
let result = unsafe { i8x32::from(_mm256_shuffle_epi8(LUT.into(), result.into())) };
#[cfg(not(all(target_feature = "avx2", not(miri))))]
let result = (LUT.cas::<c>().swizzle_dyn(result)).cas::<i8x32>();
Cast::cas(result + x.cas::<i8x32>())
}
pub fn cmpgt(x: c, y: c) -> c {
x.cas::<i8x32>().simd_gt(y.cas::<i8x32>()).cas()
}
trait P {
unsafe fn p<const N: usize>(&mut self, data: [u8; N]);
}
impl P for *mut u8 {
unsafe fn p<const N: usize>(&mut self, data: [u8; N]) {
unsafe { self.copy_from(data.as_ptr(), N) };
*self = unsafe { self.add(N) };
}
}
#[allow(unsafe_op_in_unsafe_fn)]
/// # Safety
/// ptr valid for [`size`]`(input)` writes.
pub unsafe fn encode_simple(mut input: &[u8], mut output: *mut u8) {
const Α: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
while let [a, b, c, rest @ ..] = input {
let α = ((*a as usize) << 16) | ((*b as usize) << 8) | *c as usize;
output.p([
Α[α >> 18],
Α[(α >> 12) & 0x3F],
Α[(α >> 6) & 0x3F],
Α[α & 0x3F],
]);
input = rest;
}
if !input.is_empty() {
let mut α = (input[0] as usize) << 16;
if input.len() > 1 {
α |= (input[1] as usize) << 8;
}
output.p([Α[α >> 18], Α[α >> 12 & 0x3F]]);
if input.len() > 1 {
output.p([Α[α >> 6 & 0x3f]]);
} else {
output.p([b'=']);
}
output.p([b'=']);
}
}
pub const fn size(of: &[u8]) -> usize {
let use_pad = of.len() % 3 != 0;
if use_pad {
4 * (of.len() / 3 + 1)
} else {
4 * (of.len() / 3)
}
}