1 files changed, 198 insertions, 0 deletions
diff --git a/matcher/src/matrix.rs b/matcher/src/matrix.rs
new file mode 100644
index 00000000..a91ed95f
--- /dev/null
+++ b/matcher/src/matrix.rs
@@ -0,0 +1,198 @@
+use std::alloc::{alloc_zeroed, dealloc, handle_alloc_error, Layout};
+use std::marker::PhantomData;
+use std::mem::size_of;
+use std::panic::{RefUnwindSafe, UnwindSafe};
+use std::ptr::{slice_from_raw_parts_mut, NonNull};
+
+use crate::chars::Char;
+
+const MAX_MATRIX_SIZE: usize = 100 * 1024; // 100*1024 = 100KB
+
+// these two aren't hard maxima, instead we simply allow whatever will fit into memory
+const MAX_HAYSTACK_LEN: usize = 2048; // 64KB
+const MAX_NEEDLE_LEN: usize = 2048; // 64KB
+
+struct MatrixLayout<C: Char> {
+    haystack_len: usize,
+    needle_len: usize,
+    layout: Layout,
+    haystack_off: usize,
+    bonus_off: usize,
+    rows_off: usize,
+    score_off: usize,
+    matrix_off: usize,
+    _phantom: PhantomData<C>,
+}
+impl<C: Char> MatrixLayout<C> {
+    fn new(haystack_len: usize, needle_len: usize) -> MatrixLayout<C> {
+        assert!(haystack_len >= needle_len);
+        assert!(haystack_len <= u32::MAX as usize);
+        let mut layout = Layout::from_size_align(0, 1).unwrap();
+        let haystack_layout = Layout::array::<C>(haystack_len).unwrap();
+        let bonus_layout = Layout::array::<u8>(haystack_len).unwrap();
+        let rows_layout = Layout::array::<u16>(needle_len).unwrap();
+        let score_layout = Layout::array::<ScoreCell>(haystack_len + 1 - needle_len).unwrap();
+        let matrix_layout =
+            Layout::array::<MatrixCell>((haystack_len + 1 - needle_len) * needle_len).unwrap();
+
+        let haystack_off;
+        (layout, haystack_off) = layout.extend(haystack_layout).unwrap();
+        let bonus_off;
+        (layout, bonus_off) = layout.extend(bonus_layout).unwrap();
+        let rows_off;
+        (layout, rows_off) = layout.extend(rows_layout).unwrap();
+        let score_off;
+        (layout, score_off) = layout.extend(score_layout).unwrap();
+        let matrix_off;
+        (layout, matrix_off) = layout.extend(matrix_layout).unwrap();
+        MatrixLayout {
+            haystack_len,
+            needle_len,
+            layout,
+            haystack_off,
+            bonus_off,
+            rows_off,
+            score_off,
+            matrix_off,
+            _phantom: PhantomData,
+        }
+    }
+    /// # Safety
+    ///
+    /// `ptr` must point at an allocated with MARTIX_ALLOC_LAYOUT
+    #[allow(clippy::type_complexity)]
+    unsafe fn fieds_from_ptr(
+        &self,
+        ptr: NonNull<u8>,
+    ) -> (
+        *mut [C],
+        *mut [u8],
+        *mut [u16],
+        *mut [ScoreCell],
+        *mut [MatrixCell],
+    ) {
+        let base = ptr.as_ptr();
+        let haystack = base.add(self.haystack_off) as *mut C;
+        let haystack = slice_from_raw_parts_mut(haystack, self.haystack_len);
+        let bonus = base.add(self.bonus_off);
+        let bonus = slice_from_raw_parts_mut(bonus, self.haystack_len);
+        let rows = base.add(self.rows_off) as *mut u16;
+        let rows = slice_from_raw_parts_mut(rows, self.needle_len);
+        let cells = base.add(self.score_off) as *mut ScoreCell;
+        let cells = slice_from_raw_parts_mut(cells, self.haystack_len + 1 - self.needle_len);
+        let matrix = base.add(self.matrix_off) as *mut MatrixCell;
+        let matrix = slice_from_raw_parts_mut(
+            matrix,
+            (self.haystack_len + 1 - self.needle_len) * self.haystack_len,
+        );
+        (haystack, bonus, rows, cells, matrix)
+    }
+}
+
+const _SIZE_CHECK: () = {
+    if size_of::<ScoreCell>() != 8 {
+        panic!()
+    }
+};
+
+// make this act like a u64
+#[repr(align(8))]
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub(crate) struct ScoreCell {
+    pub score: u16,
+    pub consecutive_bonus: u8,
+    pub matched: bool,
+}
+
+pub(crate) struct MatcherDataView<'a, C: Char> {
+    pub haystack: &'a mut [C],
+    // stored as a separate array instead of struct
+    // to avoid padding since char is too large and u8 too small :/
+    pub bonus: &'a mut [u8],
+    pub current_row: &'a mut [ScoreCell],
+    pub row_offs: &'a mut [u16],
+    pub matrix_cells: &'a mut [MatrixCell],
+}
+#[repr(transparent)]
+pub struct MatrixCell(pub(crate) u8);
+
+impl MatrixCell {
+    pub fn set(&mut self, p_match: bool, m_match: bool) {
+        self.0 = p_match as u8 | ((m_match as u8) << 1);
+    }
+
+    pub fn get(&self, m_matrix: bool) -> bool {
+        let mask = m_matrix as u8 + 1;
+        (self.0 & mask) != 0
+    }
+}
+
+// we only use this to construct the layout for the slab allocation
+#[allow(unused)]
+struct MatcherData {
+    haystack: [char; MAX_HAYSTACK_LEN],
+    bonus: [u8; MAX_HAYSTACK_LEN],
+    row_offs: [u16; MAX_NEEDLE_LEN],
+    scratch_space: [ScoreCell; MAX_HAYSTACK_LEN],
+    matrix: [u8; MAX_MATRIX_SIZE],
+}
+
+pub(crate) struct MatrixSlab(NonNull<u8>);
+unsafe impl Sync for MatrixSlab {}
+unsafe impl Send for MatrixSlab {}
+impl UnwindSafe for MatrixSlab {}
+impl RefUnwindSafe for MatrixSlab {}
+
+impl MatrixSlab {
+    pub fn new() -> Self {
+        let layout = Layout::new::<MatcherData>();
+        // safety: the matrix is never zero sized (hardcoded constants)
+        let ptr = unsafe { alloc_zeroed(layout) };
+        let Some(ptr) = NonNull::new(ptr) else {
+            handle_alloc_error(layout)
+        };
+        MatrixSlab(ptr.cast())
+    }
+
+    pub(crate) fn alloc<C: Char>(
+        &mut self,
+        haystack_: &[C],
+        needle_len: usize,
+    ) -> Option<MatcherDataView<'_, C>> {
+        let cells = haystack_.len() * needle_len;
+        if cells > MAX_MATRIX_SIZE
+            || haystack_.len() > u16::MAX as usize
+            // ensures that scores never overflow
+            || needle_len > MAX_NEEDLE_LEN
+        {
+            return None;
+        }
+        let matrix_layout = MatrixLayout::<C>::new(haystack_.len(), needle_len);
+        if matrix_layout.layout.size() > size_of::<MatcherData>() {
+            return None;
+        }
+        unsafe {
+            // safely: this allocation is valid for MATRIX_ALLOC_LAYOUT
+            let (haystack, bonus, rows, current_row, matrix_cells) =
+                matrix_layout.fieds_from_ptr(self.0);
+            // copy haystack before creating references to ensure we don't create
+            // references to invalid chars (which may or may not be UB)
+            haystack_
+                .as_ptr()
+                .copy_to_nonoverlapping(haystack as *mut _, haystack_.len());
+            Some(MatcherDataView {
+                haystack: &mut *haystack,
+                row_offs: &mut *rows,
+                bonus: &mut *bonus,
+                current_row: &mut *current_row,
+                matrix_cells: &mut *matrix_cells,
+            })
+        }
+    }
+}
+
+impl Drop for MatrixSlab {
+    fn drop(&mut self) {
+        unsafe { dealloc(self.0.as_ptr(), Layout::new::<MatcherData>()) };
+    }
+}