1 files changed, 26 insertions, 0 deletions
diff --git a/third_party/rust/aho-corasick/src/util/debug.rs b/third_party/rust/aho-corasick/src/util/debug.rs
new file mode 100644
index 0000000000..22b5f2231f
--- /dev/null
+++ b/third_party/rust/aho-corasick/src/util/debug.rs
@@ -0,0 +1,26 @@
+/// A type that wraps a single byte with a convenient fmt::Debug impl that
+/// escapes the byte.
+pub(crate) struct DebugByte(pub(crate) u8);
+
+impl core::fmt::Debug for DebugByte {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        // Special case ASCII space. It's too hard to read otherwise, so
+        // put quotes around it. I sometimes wonder whether just '\x20' would
+        // be better...
+        if self.0 == b' ' {
+            return write!(f, "' '");
+        }
+        // 10 bytes is enough to cover any output from ascii::escape_default.
+        let mut bytes = [0u8; 10];
+        let mut len = 0;
+        for (i, mut b) in core::ascii::escape_default(self.0).enumerate() {
+            // capitalize \xab to \xAB
+            if i >= 2 && b'a' <= b && b <= b'f' {
+                b -= 32;
+            }
+            bytes[len] = b;
+            len += 1;
+        }
+        write!(f, "{}", core::str::from_utf8(&bytes[..len]).unwrap())
+    }
+}