v0.34.0_4

src/proxy/request_id.rs

@@ -13,12 +13,14 @@ fn request_id_hash(sequence: u64) -> String {
 
 fn request_id_hex(digest: &[u8]) -> String {
     const HEX: &[u8; 16] = b"0123456789abcdef";
-    let mut encoded = String::with_capacity(digest.len() * 2);
-    for &byte in digest {
-        encoded.push(HEX[(byte >> 4) as usize] as char);
-        encoded.push(HEX[(byte & 0x0f) as usize] as char);
+    // Encode two ASCII bytes per digest byte in one allocation; avoid 64
+    // separate String::push bounds checks for the 32-byte SHA-256 digest.
+    let mut encoded = vec![0u8; digest.len() * 2];
+    for (i, &byte) in digest.iter().enumerate() {
+        encoded[2 * i] = HEX[(byte >> 4) as usize];
+        encoded[2 * i + 1] = HEX[(byte & 0x0f) as usize];
     }
-    encoded
+    String::from_utf8(encoded).expect("hex digits are always valid UTF-8")
 }
 
 #[cfg(test)]