fix(buffer): fix incorrect resizing of BufReader

Closes #715

src/buffer.rs

@@ -79,7 +79,7 @@ unsafe fn grow_zerofill(buf: &mut Vec<u8>, additional: usize) {
  use std::ptr;
  let len = buf.len();
  buf.set_len(len + additional);
- ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len());
+ ptr::write_bytes(buf.as_mut_ptr().offset(len as isize), 0, buf.len());
 }
 
 impl<R: Read> Read for BufReader<R> {
@@ -151,4 +151,14 @@ mod tests {
  assert_eq!(rdr.pos, 0);
  assert_eq!(rdr.cap, 0);
  }
+
+ #[test]
+ fn test_resize() {
+ let raw = b"hello world";
+ let mut rdr = BufReader::with_capacity(&raw[..], 5);
+ rdr.read_into_buf().unwrap();
+ assert_eq!(rdr.get_buf(), b"hello");
+ rdr.read_into_buf().unwrap();
+ assert_eq!(rdr.get_buf(), b"hello world");
+ }
 }