Fixed performance issue with contiguous (#1008) (#1009)

* Fixed performance issue with contiguous (#1008) * fixed format issue slipped in when fixing (#1008) * Update commons/zenoh-buffers/src/lib.rs Co-authored-by: Luca Cominardi <[email protected]> --------- Co-authored-by: Luca Cominardi <[email protected]>
eclipse-zenoh · May 4, 2024 · e53364f · e53364f
1 parent f5195c0
commit e53364f
Showing 1 changed file with 16 additions and 5 deletions.
diff --git a/commons/zenoh-buffers/src/lib.rs b/commons/zenoh-buffers/src/lib.rs
@@ -101,11 +101,22 @@ pub mod buffer {
             let mut slices = self.slices();
             match slices.len() {
                 0 => Cow::Borrowed(b""),
-                1 => Cow::Borrowed(slices.next().unwrap()),
-                _ => Cow::Owned(slices.fold(Vec::new(), |mut acc, it| {
-                    acc.extend(it);
-                    acc
-                })),
+                1 => {
+                    // SAFETY: unwrap here is safe because we have explicitly checked
+                    //         the iterator has 1 element.
+                    Cow::Borrowed(unsafe { slices.next().unwrap_unchecked() })
+                }
+                _ => {
+                    let mut l = 0;
+                    for s in slices.by_ref() {
+                        l += s.len();
+                    }
+                    let mut vec = Vec::with_capacity(l);
+                    for slice in slices {
+                        vec.extend_from_slice(slice);
+                    }
+                    Cow::Owned(vec)
+                }
             }
         }
     }