[incremental] Specialize encoding and decoding of Fingerprints

This saves the storage space used by about 32 bits per `Fingerprint`.
On average, this reduces the size of the `/target/{mode}/incremental`
folder by roughly 5%.

Fixes #45875

1 files changed, 4 insertions, 3 deletions

diff --git a/src/libserialize/opaque.rs b/src/libserialize/opaque.rs
index 4b2549a1aed..409366102ba 100644
--- a/src/libserialize/opaque.rs
+++ b/src/libserialize/opaque.rs
@@ -175,11 +175,12 @@ impl<'a> Decoder<'a> {
     }
 
     pub fn read_raw_bytes(&mut self, s: &mut [u8]) -> Result<(), String> {
-        let len = s.len();
+        let start = self.position;
+        let end = start + s.len();
 
-        self.position += len;
+        s.copy_from_slice(&self.data[start..end]);
 
-        s.copy_from_slice(&self.data[0..len]);
+        self.position = end;
 
         Ok(())
     }