Rollup merge of #94776 - martingms:optimize-escape-default, r=nnethercote

[rust.git] / library / core / src / ascii.rs

diff --git a/library/core/src/ascii.rs b/library/core/src/ascii.rs
index 20f2dd13d8fb401a4b89b0a550951d64a726d0b8..8a4cb78cc7f92f5a2fabedad3f3342389d7b3b48 100644 (file)
--- a/library/core/src/ascii.rs
+++ b/library/core/src/ascii.rs
@@ -99,29 +99,19 @@ pub fn escape_default(c: u8) -> EscapeDefault {
         b'"' => ([b'\\', b'"', 0, 0], 2),
         b'\x20'..=b'\x7e' => ([c, 0, 0, 0], 1),
         _ => {
-            let (b1, b2) = hexify(c);
-            ([b'\\', b'x', b1, b2], 4)
+            let hex_digits: &[u8; 16] = b"0123456789abcdef";
+            ([b'\\', b'x', hex_digits[(c >> 4) as usize], hex_digits[(c & 0xf) as usize]], 4)
         }
     };
 
     return EscapeDefault { range: 0..len, data };
-
-    #[inline]
-    fn hexify(b: u8) -> (u8, u8) {
-        let hex_digits: &[u8; 16] = b"0123456789abcdef";
-        // SAFETY: For all n: u8, n >> 4 < 16 and n & 0xf < 16
-        unsafe {
-            (
-                *hex_digits.get_unchecked((b >> 4) as usize),
-                *hex_digits.get_unchecked((b & 0xf) as usize),
-            )
-        }
-    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Iterator for EscapeDefault {
     type Item = u8;
+
+    #[inline]
     fn next(&mut self) -> Option<u8> {
         self.range.next().map(|i| self.data[i as usize])
     }