build(rust): vendor rnix parser crate

third_party/crates/rowan-0.16.1/src/sll.rs

@@ -0,0 +1,128 @@
+//! Sorted Linked List
+
+use std::{cell::Cell, cmp::Ordering, ptr};
+
+use crate::utility_types::Delta;
+pub(crate) unsafe trait Elem {
+    fn prev(&self) -> &Cell<*const Self>;
+    fn next(&self) -> &Cell<*const Self>;
+    fn key(&self) -> &Cell<u32>;
+}
+
+pub(crate) enum AddToSllResult<'a, E: Elem> {
+    NoHead,
+    EmptyHead(&'a Cell<*const E>),
+    SmallerThanHead(&'a Cell<*const E>),
+    SmallerThanNotHead(*const E),
+    AlreadyInSll(*const E),
+}
+
+impl<'a, E: Elem> AddToSllResult<'a, E> {
+    pub(crate) fn add_to_sll(&self, elem_ptr: *const E) {
+        unsafe {
+            (*elem_ptr).prev().set(elem_ptr);
+            (*elem_ptr).next().set(elem_ptr);
+
+            match self {
+                // Case 1: empty head, replace it.
+                AddToSllResult::EmptyHead(head) => head.set(elem_ptr),
+
+                // Case 2: we are smaller than the head, replace it.
+                AddToSllResult::SmallerThanHead(head) => {
+                    let old_head = head.get();
+                    let prev = (*old_head).prev().replace(elem_ptr);
+                    (*prev).next().set(elem_ptr);
+                    (*elem_ptr).next().set(old_head);
+                    (*elem_ptr).prev().set(prev);
+                    head.set(elem_ptr);
+                }
+
+                // Case 3: insert in place found by looping
+                AddToSllResult::SmallerThanNotHead(curr) => {
+                    let next = (**curr).next().replace(elem_ptr);
+                    (*next).prev().set(elem_ptr);
+                    (*elem_ptr).prev().set(*curr);
+                    (*elem_ptr).next().set(next);
+                }
+                AddToSllResult::NoHead | AddToSllResult::AlreadyInSll(_) => (),
+            }
+        }
+    }
+}
+
+#[cold]
+pub(crate) fn init<'a, E: Elem>(
+    head: Option<&'a Cell<*const E>>,
+    elem: &E,
+) -> AddToSllResult<'a, E> {
+    if let Some(head) = head {
+        link(head, elem)
+    } else {
+        AddToSllResult::NoHead
+    }
+}
+
+#[cold]
+pub(crate) fn unlink<E: Elem>(head: &Cell<*const E>, elem: &E) {
+    debug_assert!(!head.get().is_null(), "invalid linked list head");
+
+    let elem_ptr: *const E = elem;
+
+    let prev = elem.prev().replace(elem_ptr);
+    let next = elem.next().replace(elem_ptr);
+    unsafe {
+        debug_assert_eq!((*prev).next().get(), elem_ptr, "invalid linked list links");
+        debug_assert_eq!((*next).prev().get(), elem_ptr, "invalid linked list links");
+        (*prev).next().set(next);
+        (*next).prev().set(prev);
+    }
+
+    if head.get() == elem_ptr {
+        head.set(if next == elem_ptr { ptr::null() } else { next })
+    }
+}
+
+#[cold]
+pub(crate) fn link<'a, E: Elem>(head: &'a Cell<*const E>, elem: &E) -> AddToSllResult<'a, E> {
+    let old_head = head.get();
+    // Case 1: empty head, replace it.
+    if old_head.is_null() {
+        return AddToSllResult::EmptyHead(head);
+    }
+    unsafe {
+        // Case 2: we are smaller than the head, replace it.
+        if elem.key() < (*old_head).key() {
+            return AddToSllResult::SmallerThanHead(head);
+        }
+
+        // Case 3: loop *backward* until we find insertion place. Because of
+        // Case 2, we can't loop beyond the head.
+        let mut curr = (*old_head).prev().get();
+        loop {
+            match (*curr).key().cmp(elem.key()) {
+                Ordering::Less => return AddToSllResult::SmallerThanNotHead(curr),
+                Ordering::Equal => return AddToSllResult::AlreadyInSll(curr),
+                Ordering::Greater => curr = (*curr).prev().get(),
+            }
+        }
+    }
+}
+
+pub(crate) fn adjust<E: Elem>(elem: &E, from: u32, by: Delta<u32>) {
+    let elem_ptr: *const E = elem;
+
+    unsafe {
+        let mut curr = elem_ptr;
+        loop {
+            let mut key = (*curr).key().get();
+            if key >= from {
+                key += by;
+                (*curr).key().set(key);
+            }
+            curr = (*curr).next().get();
+            if curr == elem_ptr {
+                break;
+            }
+        }
+    }
+}