Small improvements of `hex_utils`

diff --git a/src/hex_utils.rs b/src/hex_utils.rs
index 6077a60c52fe5b19b61c4492ce1d07af4cd77e8c..8b853dbb6330826132096a7c2c55f204592be486 100644 (file)
--- a/src/hex_utils.rs
+++ b/src/hex_utils.rs
@@ -1,4 +1,5 @@
 use bitcoin::secp256k1::PublicKey;
+use std::fmt::Write;
 
 pub fn to_vec(hex: &str) -> Option<Vec<u8>> {
        let mut out = Vec::with_capacity(hex.len() / 2);
@@ -23,9 +24,9 @@ pub fn to_vec(hex: &str) -> Option<Vec<u8>> {
 
 #[inline]
 pub fn hex_str(value: &[u8]) -> String {
-       let mut res = String::with_capacity(64);
+       let mut res = String::with_capacity(2 * value.len());
        for v in value {
-               res += &format!("{:02x}", v);
+               write!(&mut res, "{:02x}", v).expect("Unable to write");
        }
        res
 }