split: Reduce malloc

src/uu/split/src/split.rs

@@ -1156,7 +1156,7 @@ where
         out_files = OutFiles::init(num_chunks, settings, false)?;
     }
 
-    let buf = &mut Vec::new();
+    let mut buf = Vec::with_capacity((chunk_size_base + 1) as usize);
     for i in 1_u64..=num_chunks {
         let chunk_size = chunk_size_base + (chunk_size_reminder > i - 1) as u64;
         buf.clear();
@@ -1175,7 +1175,7 @@ where
                 }
             };
 
-            let n_bytes_read = reader.by_ref().take(limit).read_to_end(buf);
+            let n_bytes_read = reader.by_ref().take(limit).read_to_end(&mut buf);
 
             match n_bytes_read {
                 Ok(n_bytes) => {
@@ -1191,13 +1191,13 @@ where
 
             if let Some(chunk_number) = kth_chunk {
                 if i == chunk_number {
-                    stdout_writer.write_all(buf)?;
+                    stdout_writer.write_all(&buf)?;
                     break;
                 }
             } else {
                 let idx = (i - 1) as usize;
                 let writer = out_files.get_writer(idx, settings)?;
-                writer.write_all(buf)?;
+                writer.write_all(&buf)?;
             }
         } else {
             break;