1 files changed, 74 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/util/memchr.rs b/third_party/rust/tokio/src/util/memchr.rs
new file mode 100644
index 0000000000..44fd2da371
--- /dev/null
+++ b/third_party/rust/tokio/src/util/memchr.rs
@@ -0,0 +1,74 @@
+//! Search for a byte in a byte array using libc.
+//!
+//! When nothing pulls in libc, then just use a trivial implementation. Note
+//! that we only depend on libc on unix.
+
+#[cfg(not(all(unix, feature = "libc")))]
+pub(crate) fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
+    haystack.iter().position(|val| needle == *val)
+}
+
+#[cfg(all(unix, feature = "libc"))]
+pub(crate) fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
+    let start = haystack.as_ptr();
+
+    // SAFETY: `start` is valid for `haystack.len()` bytes.
+    let ptr = unsafe { libc::memchr(start.cast(), needle as _, haystack.len()) };
+
+    if ptr.is_null() {
+        None
+    } else {
+        Some(ptr as usize - start as usize)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::memchr;
+
+    #[test]
+    fn memchr_test() {
+        let haystack = b"123abc456\0\xffabc\n";
+
+        assert_eq!(memchr(b'1', haystack), Some(0));
+        assert_eq!(memchr(b'2', haystack), Some(1));
+        assert_eq!(memchr(b'3', haystack), Some(2));
+        assert_eq!(memchr(b'4', haystack), Some(6));
+        assert_eq!(memchr(b'5', haystack), Some(7));
+        assert_eq!(memchr(b'6', haystack), Some(8));
+        assert_eq!(memchr(b'7', haystack), None);
+        assert_eq!(memchr(b'a', haystack), Some(3));
+        assert_eq!(memchr(b'b', haystack), Some(4));
+        assert_eq!(memchr(b'c', haystack), Some(5));
+        assert_eq!(memchr(b'd', haystack), None);
+        assert_eq!(memchr(b'A', haystack), None);
+        assert_eq!(memchr(0, haystack), Some(9));
+        assert_eq!(memchr(0xff, haystack), Some(10));
+        assert_eq!(memchr(0xfe, haystack), None);
+        assert_eq!(memchr(1, haystack), None);
+        assert_eq!(memchr(b'\n', haystack), Some(14));
+        assert_eq!(memchr(b'\r', haystack), None);
+    }
+
+    #[test]
+    fn memchr_all() {
+        let mut arr = Vec::new();
+        for b in 0..=255 {
+            arr.push(b);
+        }
+        for b in 0..=255 {
+            assert_eq!(memchr(b, &arr), Some(b as usize));
+        }
+        arr.reverse();
+        for b in 0..=255 {
+            assert_eq!(memchr(b, &arr), Some(255 - b as usize));
+        }
+    }
+
+    #[test]
+    fn memchr_empty() {
+        for b in 0..=255 {
+            assert_eq!(memchr(b, b""), None);
+        }
+    }
+}