feat: implement check for arm and portable-simd (#10)

.github/workflows/ci.yml

@@ -40,11 +40,11 @@ jobs:
       - uses: Swatinem/rust-cache@v2
 
       - run: cargo build
-      - run: cargo test
       - run: cargo build --no-default-features
-      - run: cargo test --tests --no-default-features
-      - run: cargo test --tests --no-default-features --features force-generic
-      - run: cargo test --tests --no-default-features --features nightly,portable-simd
+      - run: cargo test
+      - run: cargo test --no-default-features
+      - run: cargo test --no-default-features --features force-generic
+      - run: cargo test --no-default-features --features nightly,portable-simd
         if: matrix.rust == 'nightly'
       - run: cargo bench --no-run
         if: matrix.rust == 'nightly'
@@ -65,8 +65,6 @@ jobs:
       - uses: dtolnay/rust-toolchain@miri
         with:
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v2
-      - run: cargo miri setup --target ${{ matrix.target }} ${{ matrix.flags }}
       - run: cargo miri test --target ${{ matrix.target }} ${{ matrix.flags }}
 
   fuzz:

benches/bench/main.rs

@@ -29,6 +29,50 @@ impl<const N: usize> fmt::Display for StdFormat<N> {
 
 macro_rules! benches {
     ($($name:ident($enc:expr, $dec:expr))*) => {
+        mod check {
+            use super::*;
+
+            mod const_hex {
+                use super::*;
+
+                $(
+                    #[bench]
+                    fn $name(b: &mut Bencher) {
+                        b.iter(|| {
+                            ::const_hex::check(black_box($dec))
+                        });
+                    }
+                )*
+            }
+
+            mod faster_hex {
+                use super::*;
+
+                $(
+                    #[bench]
+                    fn $name(b: &mut Bencher) {
+                        b.iter(|| {
+                            ::faster_hex::hex_check(black_box($dec.as_bytes()))
+                        });
+                    }
+                )*
+            }
+
+            mod naive {
+                use super::*;
+
+                $(
+                    #[bench]
+                    fn $name(b: &mut Bencher) {
+                        b.iter(|| {
+                            let dec = black_box($dec.as_bytes());
+                            dec.iter().all(u8::is_ascii_hexdigit)
+                        });
+                    }
+                )*
+            }
+        }
+
         #[cfg(feature = "alloc")]
         mod decode {
             use super::*;

src/arch/aarch64.rs

@@ -4,7 +4,7 @@ use super::generic;
 use crate::get_chars_table;
 use core::arch::aarch64::*;
 
-pub(crate) const USE_CHECK_FN: bool = false;
+pub(crate) const USE_CHECK_FN: bool = true;
 const CHUNK_SIZE: usize = core::mem::size_of::<uint8x16_t>();
 
 cfg_if::cfg_if! {
@@ -63,6 +63,44 @@ pub(crate) unsafe fn encode_neon<const UPPER: bool>(input: &[u8], output: *mut u
     }
 }
 
-pub(crate) use generic::check;
+#[inline]
+pub(crate) fn check(input: &[u8]) -> bool {
+    if cfg!(miri) || !has_neon() || input.len() < CHUNK_SIZE {
+        return generic::check(input);
+    }
+    unsafe { check_neon(input) }
+}
+
+#[target_feature(enable = "neon")]
+pub(crate) unsafe fn check_neon(input: &[u8]) -> bool {
+    let ascii_zero = vdupq_n_u8(b'0' - 1);
+    let ascii_nine = vdupq_n_u8(b'9' + 1);
+    let ascii_ua = vdupq_n_u8(b'A' - 1);
+    let ascii_uf = vdupq_n_u8(b'F' + 1);
+    let ascii_la = vdupq_n_u8(b'a' - 1);
+    let ascii_lf = vdupq_n_u8(b'f' + 1);
+
+    let (prefix, chunks, suffix) = input.align_to::<uint8x16_t>();
+    generic::check(prefix)
+        && chunks.iter().all(|&chunk| {
+            let ge0 = vcgtq_u8(chunk, ascii_zero);
+            let le9 = vcltq_u8(chunk, ascii_nine);
+            let valid_digit = vandq_u8(ge0, le9);
+
+            let geua = vcgtq_u8(chunk, ascii_ua);
+            let leuf = vcltq_u8(chunk, ascii_uf);
+            let valid_upper = vandq_u8(geua, leuf);
+
+            let gela = vcgtq_u8(chunk, ascii_la);
+            let lelf = vcltq_u8(chunk, ascii_lf);
+            let valid_lower = vandq_u8(gela, lelf);
+
+            let valid_letter = vorrq_u8(valid_lower, valid_upper);
+            let valid_mask = vorrq_u8(valid_digit, valid_letter);
+            vminvq_u8(valid_mask) == 0xFF
+        })
+        && generic::check(suffix)
+}
+
 pub(crate) use generic::decode_checked;
 pub(crate) use generic::decode_unchecked;

src/arch/generic.rs

@@ -24,8 +24,8 @@ pub(crate) unsafe fn encode<const UPPER: bool>(input: &[u8], output: *mut u8) {
 /// Default check function.
 #[inline]
 pub(crate) const fn check(mut input: &[u8]) -> bool {
-    while let [byte, rest @ ..] = input {
-        if HEX_DECODE_LUT[*byte as usize] == NIL {
+    while let &[byte, ref rest @ ..] = input {
+        if HEX_DECODE_LUT[byte as usize] == NIL {
             return false;
         }
         input = rest;
@@ -48,8 +48,9 @@ pub(crate) unsafe fn decode_checked(input: &[u8], output: &mut [u8]) -> bool {
 ///
 /// Assumes `output.len() == input.len() / 2` and that the input is valid hex.
 pub(crate) unsafe fn decode_unchecked(input: &[u8], output: &mut [u8]) {
-    let r = unsafe { decode_maybe_check::<false>(input, output) };
-    debug_assert!(r);
+    #[allow(unused_braces)] // False positive on older rust versions.
+    let success = unsafe { decode_maybe_check::<{ cfg!(debug_assertions) }>(input, output) };
+    debug_assert!(success);
 }
 
 /// Default decoding function. Checks input validity if `CHECK` is `true`, otherwise assumes it.
@@ -67,8 +68,6 @@ unsafe fn decode_maybe_check<const CHECK: bool>(input: &[u8], output: &mut [u8])
                 if $var == NIL {
                     return false;
                 }
-            } else {
-                debug_assert_ne!($var, NIL, "invalid hex input");
             }
         };
     }

src/arch/portable_simd.rs

@@ -1,10 +1,12 @@
 use super::generic;
 use crate::get_chars_table;
-use core::simd::u8x16;
+use core::simd::prelude::*;
 use core::slice;
 
-pub(crate) const USE_CHECK_FN: bool = false;
-const CHUNK_SIZE: usize = core::mem::size_of::<u8x16>();
+type Simd = u8x16;
+
+pub(crate) const USE_CHECK_FN: bool = true;
+const CHUNK_SIZE: usize = core::mem::size_of::<Simd>();
 
 pub(crate) unsafe fn encode<const UPPER: bool>(input: &[u8], output: *mut u8) {
     let mut i = 0;
@@ -14,18 +16,18 @@ pub(crate) unsafe fn encode<const UPPER: bool>(input: &[u8], output: *mut u8) {
     unsafe { generic::encode::<UPPER>(prefix, output) };
     i += prefix.len() * 2;
 
-    let hex_table = u8x16::from_array(*get_chars_table::<UPPER>());
+    let hex_table = Simd::from_array(*get_chars_table::<UPPER>());
     for &chunk in chunks {
         // Load input bytes and mask to nibbles.
-        let mut lo = chunk & u8x16::splat(15);
-        let mut hi = chunk >> u8x16::splat(4);
+        let mut lo = chunk & Simd::splat(15);
+        let mut hi = chunk >> Simd::splat(4);
 
         // Lookup the corresponding ASCII hex digit for each nibble.
         lo = hex_table.swizzle_dyn(lo);
         hi = hex_table.swizzle_dyn(hi);
 
         // Interleave the nibbles ([hi[0], lo[0], hi[1], lo[1], ...]).
-        let (hex_lo, hex_hi) = u8x16::interleave(hi, lo);
+        let (hex_lo, hex_hi) = Simd::interleave(hi, lo);
 
         // Store result into the output buffer.
         // SAFETY: ensured by caller.
@@ -41,6 +43,18 @@ pub(crate) unsafe fn encode<const UPPER: bool>(input: &[u8], output: *mut u8) {
     unsafe { generic::encode::<UPPER>(suffix, output.add(i)) };
 }
 
-pub(crate) use generic::check;
+pub(crate) fn check(input: &[u8]) -> bool {
+    let (prefix, chunks, suffix) = input.as_simd::<CHUNK_SIZE>();
+    generic::check(prefix)
+        && chunks.iter().all(|&chunk| {
+            let valid_digit = chunk.simd_ge(Simd::splat(b'0')) & chunk.simd_le(Simd::splat(b'9'));
+            let valid_upper = chunk.simd_ge(Simd::splat(b'A')) & chunk.simd_le(Simd::splat(b'F'));
+            let valid_lower = chunk.simd_ge(Simd::splat(b'a')) & chunk.simd_le(Simd::splat(b'f'));
+            let valid = valid_digit | valid_upper | valid_lower;
+            valid.all()
+        })
+        && generic::check(suffix)
+}
+
 pub(crate) use generic::decode_checked;
 pub(crate) use generic::decode_unchecked;

src/arch/x86.rs

@@ -12,8 +12,6 @@ pub(crate) const USE_CHECK_FN: bool = true;
 const CHUNK_SIZE_SSE: usize = core::mem::size_of::<__m128i>();
 const CHUNK_SIZE_AVX: usize = core::mem::size_of::<__m256i>();
 
-const T_MASK: i32 = 65535;
-
 cfg_if::cfg_if! {
     if #[cfg(feature = "std")] {
         #[inline(always)]
@@ -58,11 +56,11 @@ unsafe fn encode_ssse3<const UPPER: bool>(input: &[u8], output: *mut u8) {
     let input_remainder = input_chunks.remainder();
 
     let mut i = 0;
-    for input_chunk in input_chunks {
+    for chunk in input_chunks {
         // Load input bytes and mask to nibbles.
-        let input_bytes = _mm_loadu_si128(input_chunk.as_ptr().cast());
-        let mut lo = _mm_and_si128(input_bytes, mask_lo);
-        let mut hi = _mm_srli_epi32::<4>(_mm_and_si128(input_bytes, mask_hi));
+        let chunk = _mm_loadu_si128(chunk.as_ptr().cast());
+        let mut lo = _mm_and_si128(chunk, mask_lo);
+        let mut hi = _mm_srli_epi32::<4>(_mm_and_si128(chunk, mask_hi));
 
         // Lookup the corresponding ASCII hex digit for each nibble.
         lo = _mm_shuffle_epi8(hex_table, lo);
@@ -101,32 +99,26 @@ unsafe fn check_sse2(input: &[u8]) -> bool {
     let ascii_la = _mm_set1_epi8((b'a' - 1) as i8);
     let ascii_lf = _mm_set1_epi8((b'f' + 1) as i8);
 
-    let input_chunks = input.chunks_exact(CHUNK_SIZE_SSE);
-    let input_remainder = input_chunks.remainder();
-    for input_chunk in input_chunks {
-        let unchecked = _mm_loadu_si128(input_chunk.as_ptr().cast());
-
-        let gt0 = _mm_cmpgt_epi8(unchecked, ascii_zero);
-        let lt9 = _mm_cmplt_epi8(unchecked, ascii_nine);
-        let valid_digit = _mm_and_si128(gt0, lt9);
-
-        let gtua = _mm_cmpgt_epi8(unchecked, ascii_ua);
-        let ltuf = _mm_cmplt_epi8(unchecked, ascii_uf);
-
-        let gtla = _mm_cmpgt_epi8(unchecked, ascii_la);
-        let ltlf = _mm_cmplt_epi8(unchecked, ascii_lf);
-
-        let valid_lower = _mm_and_si128(gtla, ltlf);
-        let valid_upper = _mm_and_si128(gtua, ltuf);
-        let valid_letter = _mm_or_si128(valid_lower, valid_upper);
-
-        let ret = _mm_movemask_epi8(_mm_or_si128(valid_digit, valid_letter));
-        if ret != T_MASK {
-            return false;
-        }
-    }
-
-    generic::check(input_remainder)
+    let (prefix, chunks, suffix) = input.align_to::<__m128i>();
+    generic::check(prefix)
+        && chunks.iter().all(|&chunk| {
+            let ge0 = _mm_cmpgt_epi8(chunk, ascii_zero);
+            let le9 = _mm_cmplt_epi8(chunk, ascii_nine);
+            let valid_digit = _mm_and_si128(ge0, le9);
+
+            let geua = _mm_cmpgt_epi8(chunk, ascii_ua);
+            let leuf = _mm_cmplt_epi8(chunk, ascii_uf);
+            let valid_upper = _mm_and_si128(geua, leuf);
+
+            let gela = _mm_cmpgt_epi8(chunk, ascii_la);
+            let lelf = _mm_cmplt_epi8(chunk, ascii_lf);
+            let valid_lower = _mm_and_si128(gela, lelf);
+
+            let valid_letter = _mm_or_si128(valid_lower, valid_upper);
+            let valid_mask = _mm_movemask_epi8(_mm_or_si128(valid_digit, valid_letter));
+            valid_mask == 0xffff
+        })
+        && generic::check(suffix)
 }
 
 #[inline]

src/lib.rs

@@ -21,7 +21,7 @@
 #![cfg_attr(
     feature = "nightly",
     feature(core_intrinsics, inline_const),
-    allow(internal_features)
+    allow(internal_features, stable_features)
 )]
 #![cfg_attr(feature = "portable-simd", feature(portable_simd))]
 #![warn(