1 files changed, 39 insertions, 0 deletions
diff --git a/third_party/rust/aho-corasick/src/packed/ext.rs b/third_party/rust/aho-corasick/src/packed/ext.rs
new file mode 100644
index 0000000000..b689642bca
--- /dev/null
+++ b/third_party/rust/aho-corasick/src/packed/ext.rs
@@ -0,0 +1,39 @@
+/// A trait for adding some helper routines to pointers.
+pub(crate) trait Pointer {
+    /// Returns the distance, in units of `T`, between `self` and `origin`.
+    ///
+    /// # Safety
+    ///
+    /// Same as `ptr::offset_from` in addition to `self >= origin`.
+    unsafe fn distance(self, origin: Self) -> usize;
+
+    /// Casts this pointer to `usize`.
+    ///
+    /// Callers should not convert the `usize` back to a pointer if at all
+    /// possible. (And if you believe it's necessary, open an issue to discuss
+    /// why. Otherwise, it has the potential to violate pointer provenance.)
+    /// The purpose of this function is just to be able to do arithmetic, i.e.,
+    /// computing offsets or alignments.
+    fn as_usize(self) -> usize;
+}
+
+impl<T> Pointer for *const T {
+    unsafe fn distance(self, origin: *const T) -> usize {
+        // TODO: Replace with `ptr::sub_ptr` once stabilized.
+        usize::try_from(self.offset_from(origin)).unwrap_unchecked()
+    }
+
+    fn as_usize(self) -> usize {
+        self as usize
+    }
+}
+
+impl<T> Pointer for *mut T {
+    unsafe fn distance(self, origin: *mut T) -> usize {
+        (self as *const T).distance(origin as *const T)
+    }
+
+    fn as_usize(self) -> usize {
+        (self as *const T).as_usize()
+    }
+}