perf(random): use pre-allocated buffers for random

README.md

@@ -36,10 +36,10 @@ were performed on Framework Laptop (A6) with an 11th Gen Intel® Core™ i7-1165
 for 30 seconds using one thread.
 
 ```
-  counter: 163,504,123 hashes (5,461,682.8102/s)
-   header: 124,617,875 hashes (4,150,993.2260/s)
-   random: 110,886,440 hashes (3,715,452.2177/s)
-increment: 107,137,532 hashes (3,573,438.8338/s)
+  counter: 162,092,475 hashes (5,397,324.7345/s)
+   header: 139,819,851 hashes (4,632,819.3559/s)
+   random: 125,880,577 hashes (4,205,520.4347/s)
+increment: 101,819,680 hashes (3,361,825.5571/s)
  sequoia*:     864,486 hashes (   28,923.1870/s)
   sequoia:     339,407 hashes (   11,403.6102/s)
 gpg-agent:         353 hashes (       11.7519/s)

src/main.rs

@@ -494,6 +494,8 @@ fn main() -> Result<()> {
             let mut sha1 = Sha1::default();
             let mut buffer = itoa::Buffer::new();
             let mut count_buffer = itoa::Buffer::new();
+            let mut random_bytes = [0; 16];
+            let mut random_hex = [0; 32];
             let mut first = true;
             while !found.load(Ordering::SeqCst) {
                 let append = if gpg.is_some() || seq_key.is_some() {
@@ -501,9 +503,13 @@ fn main() -> Result<()> {
                 } else {
                     match method {
                         Method::Random => {
-                            let mut bytes = [0; 16];
-                            rand::thread_rng().fill(&mut bytes);
-                            Some(Cow::from(data_encoding::HEXLOWER.encode(&bytes)))
+                            rand::thread_rng().fill(&mut random_bytes);
+                            data_encoding::HEXLOWER.encode_mut(&random_bytes, &mut random_hex);
+                            let random = unsafe {
+                                std::str::from_utf8_unchecked(&random_hex)
+                            };
+
+                            Some(Cow::from(random))
                         }
                         Method::Counter => {
                             let count = counter.fetch_add(1, Ordering::SeqCst) + 1;
@@ -517,7 +523,7 @@ fn main() -> Result<()> {
                     let timestamp = match method {
                         Method::Decrement => timestamp.fetch_sub(1, Ordering::SeqCst) - 1,
                         Method::Increment => timestamp.fetch_add(1, Ordering::SeqCst) + 1,
-                        _ => timestamp.load(Ordering::SeqCst),
+                        _ => unreachable!(),
                     };
 
                     author_parts[author_len - 2] = buffer.format(timestamp).to_owned();