capi: readlink: only calculate path length once

Signed-off-by: Aleksa Sarai <[email protected]>

src/capi/utils.rs

@@ -131,21 +131,20 @@ pub(crate) unsafe fn copy_path_into_buffer<P: AsRef<Path>>(
 ) -> Result<c_int, Error> {
  let path = CString::new(path.as_ref().as_os_str().as_bytes())
  .expect("link from readlink should not contain any nulls");
+ // MSRV(1.79): Switch to .count_bytes().
+ let path_len = path.to_bytes().len();
 
  // If the linkbuf is null, we just return the number of bytes we
  // would've written.
  if !buf.is_null() && bufsize > 0 {
- // MSRV(1.79): Switch to .count_bytes().
- let to_copy = cmp::min(path.to_bytes().len(), bufsize);
  // SAFETY: The C caller guarantees that buf is safe to write to
  // up to bufsize bytes.
  unsafe {
+ let to_copy = cmp::min(path_len, bufsize);
  ptr::copy_nonoverlapping(path.as_ptr(), buf, to_copy);
  }
  }
-
- // MSRV(1.79): Switch to .count_bytes().
- Ok(path.to_bytes().len() as c_int)
+ Ok(path_len as c_int)
 }
 
 pub(crate) trait Leakable: Sized {