Test unsafe copying.

Use ptr::copy and ptr::copy_nonoverlapping instead of drain/extend and split_at_mut/copy_from slice. I can find no appreciable difference, but the code might as well live on in history.
Freaky · Apr 23, 2018 · 5ccea2c · 5ccea2c
1 parent f5ed673
commit 5ccea2c
Showing 1 changed file with 23 additions and 5 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -18,6 +18,7 @@ lines():    501636842 lines 30599847362 bytes in 167.17s (174.57 MB/s)
 use std::cmp;
 use std::io;
 use std::io::ErrorKind;
+use std::ptr;
 
 extern crate memchr;
 use memchr::{memchr, memrchr};
@@ -219,12 +220,29 @@ impl<R: io::Read> LineReader<R> {
         let fragment_len = self.end_of_buffer - self.end_of_complete;
         if fragment_len > 0 {
             if fragment_len > self.end_of_complete {
-                // Overlaps - hopefully quite rare.
-                self.buf.drain(..self.end_of_complete);
-                self.buf.extend(vec![0; self.end_of_complete]);
+                unsafe {
+                    ptr::copy(
+                        (&mut self.buf[self.end_of_complete..self.end_of_buffer]).as_mut_ptr(),
+                        self.buf.as_mut_ptr(),
+                        fragment_len,
+                    );
+                }
+
+            // Overlaps - hopefully quite rare.
+
+            // self.buf.drain(..self.end_of_complete);
+            // self.buf.extend(vec![0_u8; self.end_of_complete]);
             } else {
-                let (start, rest) = self.buf.split_at_mut(self.end_of_complete);
-                start[0..fragment_len].copy_from_slice(&rest[0..fragment_len]);
+                unsafe {
+                    ptr::copy_nonoverlapping(
+                        (&mut self.buf[self.end_of_complete..self.end_of_buffer]).as_mut_ptr(),
+                        self.buf.as_mut_ptr(),
+                        fragment_len,
+                    );
+                }
+
+                // let (start, rest) = self.buf.split_at_mut(self.end_of_complete);
+                // start[0..fragment_len].copy_from_slice(&rest[0..fragment_len]);
             }
             self.end_of_buffer = fragment_len;
         } else {