1 files changed, 154 insertions, 0 deletions
diff --git a/users/edef/refscan/src/lib.rs b/users/edef/refscan/src/lib.rs
new file mode 100644
index 000000000000..3d4a07f3dd1c
--- /dev/null
+++ b/users/edef/refscan/src/lib.rs
@@ -0,0 +1,154 @@
+// SPDX-FileCopyrightText: edef <edef@edef.eu>
+// SPDX-License-Identifier: MPL-2.0
+
+use self::simd::u8x32;
+
+fn prefilter(haystack: u8x32) -> u32 {
+    let alp = haystack.gt(u8x32::splat(b'a' - 1)) & haystack.lt(u8x32::splat(b'z' + 1));
+    let num = haystack.gt(u8x32::splat(b'0' - 1)) & haystack.lt(u8x32::splat(b'9' + 1));
+    alp | num
+}
+
+/// scan_clean returns `Err(&buffer[..n])` of known pointer-free data,
+/// or `Ok(buffer)` if the entire buffer is pointer-free.
+pub fn scan_clean(buffer: &[u8]) -> Result<&[u8], &[u8]> {
+    let buffer = {
+        let n = buffer.len() & !31;
+        &buffer[..n]
+    };
+
+    let mut masks = buffer
+        .chunks_exact(32)
+        .map(|chunk| prefilter(u8x32::from_slice_unaligned(chunk)))
+        .enumerate()
+        .map(|e| (e.0 * 32, e.1))
+        .peekable();
+
+    while let Some((offset, mask)) = masks.next() {
+        let peek = masks.peek().map(|x| x.1).unwrap_or(!0 >> 1);
+        let n = (!mask).leading_zeros() + (!peek).trailing_zeros();
+        if n >= 32 {
+            let offset = offset + mask.trailing_zeros() as usize;
+            return Err(&buffer[..offset]);
+        }
+    }
+
+    Ok(buffer)
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn scan_tail() {
+        let buffer = b"_xfbmj7sl2ikicym9x3yq7cms5qx1w39k";
+        assert_eq!(crate::scan_clean(buffer), Err(&buffer[..1]));
+    }
+    #[test]
+    fn scan_straddle() {
+        let buffer = b"________________xfbmj7sl2ikicym9x3yq7cms5qx1w39k________________";
+        assert_eq!(crate::scan_clean(buffer), Err(&buffer[..16]));
+    }
+    #[test]
+    fn scan_clean() {
+        let buffer = b"x_______________xfbmj7sl2ikicym9x3yq-cms5qx1w3-k________________";
+        assert_eq!(crate::scan_clean(buffer), Ok(&buffer[..]));
+    }
+}
+
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+mod simd {
+    #[cfg(target_arch = "x86")]
+    use std::arch::x86 as arch;
+    #[cfg(target_arch = "x86_64")]
+    use std::arch::x86_64 as arch;
+    use {
+        arch::{__m256i, _mm256_cmpgt_epi8, _mm256_movemask_epi8, _mm256_set1_epi8},
+        std::ptr,
+    };
+
+    #[allow(non_camel_case_types)]
+    #[derive(Copy, Clone)]
+    pub struct u8x32(__m256i);
+
+    impl u8x32 {
+        #[inline(always)]
+        pub fn from_slice_unaligned(slice: &[u8]) -> Self {
+            assert_eq!(slice.len(), 32);
+            u8x32(unsafe { ptr::read_unaligned(slice.as_ptr().cast()) })
+        }
+
+        #[inline(always)]
+        pub fn splat(x: u8) -> Self {
+            u8x32(unsafe { _mm256_set1_epi8(x as i8) })
+        }
+
+        #[inline(always)]
+        pub fn gt(self, b: Self) -> u32 {
+            unsafe { _mm256_movemask_epi8(_mm256_cmpgt_epi8(self.0, b.0)) as u32 }
+        }
+
+        #[inline(always)]
+        pub fn lt(self, b: Self) -> u32 {
+            b.gt(self)
+        }
+    }
+}
+
+#[cfg(target_arch = "aarch64")]
+mod simd {
+    use std::{
+        arch::aarch64::{
+            uint8x16_t as u8x16, vaddv_u8, vandq_u8, vcgtq_u8, vdupq_n_u8, vget_high_u8,
+            vget_low_u8, vshlq_u8,
+        },
+        mem, ptr,
+    };
+
+    #[allow(non_camel_case_types)]
+    #[derive(Copy, Clone)]
+    #[repr(transparent)]
+    pub struct u8x32([u8x16; 2]);
+
+    impl u8x32 {
+        #[cfg(target_endian = "little")]
+        #[inline(always)]
+        pub fn from_slice_unaligned(slice: &[u8]) -> Self {
+            assert_eq!(slice.len(), 32);
+            u8x32(unsafe { ptr::read_unaligned(slice.as_ptr().cast()) })
+        }
+
+        #[inline(always)]
+        pub fn splat(x: u8) -> Self {
+            u8x32(unsafe {
+                let x = vdupq_n_u8(x);
+                [x, x]
+            })
+        }
+
+        #[inline(always)]
+        pub fn gt(&self, b: Self) -> u32 {
+            let u8x32([al, ah]) = *self;
+            let u8x32([bl, bh]) = b;
+
+            fn f(a: u8x16, b: u8x16) -> u32 {
+                unsafe {
+                    let c = vshlq_u8(
+                        vandq_u8(vdupq_n_u8(0x80), vcgtq_u8(a, b)),
+                        mem::transmute([
+                            -7, -6, -5, -4, -3, -2, -1, 0, -7, -6, -5, -4, -3, -2, -1, 0i8,
+                        ]),
+                    );
+
+                    (vaddv_u8(vget_low_u8(c)) as u32) << 0 | (vaddv_u8(vget_high_u8(c)) as u32) << 8
+                }
+            }
+
+            f(al, bl) << 0 | f(ah, bh) << 16
+        }
+
+        #[inline(always)]
+        pub fn lt(self, b: Self) -> u32 {
+            b.gt(self)
+        }
+    }
+}