Merge #914

914: Make preadv take immutable slice of IoVecs r=asomers a=farnoy

fixes #913

I filled in the CHANGELOG, but I see that it usually links to PRs and not issues, do you want me to change it or remove and leave for you to describe?

This change seems to be strictly backwards-compatible, I didn't have to change the test for it to work.

Co-authored-by: Jakub Okoński <jakub@okonski.org>

CHANGELOG.md

@@ -10,6 +10,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 ### Fixed
+- Made `preadv` take immutable slice of IoVec.
+  ([#914](https://github.com/nix-rust/nix/pull/914))
 
 ### Removed
 

src/sys/uio.rs

@@ -51,7 +51,7 @@ pub fn pwritev(fd: RawFd, iov: &[IoVec<&[u8]>],
           target_os = "linux",
           target_os = "netbsd",
           target_os = "openbsd"))]
-pub fn preadv(fd: RawFd, iov: &mut [IoVec<&mut [u8]>],
+pub fn preadv(fd: RawFd, iov: &[IoVec<&mut [u8]>],
               offset: off_t) -> Result<usize> {
     let res = unsafe {
         libc::preadv(fd, iov.as_ptr() as *const libc::iovec, iov.len() as c_int, offset)

test/sys/test_uio.rs

@@ -182,9 +182,9 @@ fn test_preadv() {
 
     {
         // Borrow the buffers into IoVecs and preadv into them
-        let mut iovecs: Vec<_> = buffers.iter_mut().map(
+        let iovecs: Vec<_> = buffers.iter_mut().map(
             |buf| IoVec::from_mut_slice(&mut buf[..])).collect();
-        assert_eq!(Ok(100), preadv(file.as_raw_fd(), &mut iovecs, 100));
+        assert_eq!(Ok(100), preadv(file.as_raw_fd(), &iovecs, 100));
     }
 
     let all = buffers.concat();