MapFlags netbsd/freebsd constant additions.

Related to page alignment, adding map_aligned for custom alignment
requirements.

Author: devnexen

src/sys/mman.rs

@@ -209,11 +209,13 @@ libc_bitflags! {
         #[cfg_attr(docsrs, doc(cfg(all())))]
         MAP_ALIGNMENT_64PB;
         /// Right operand value for the page alignment bitshift calculation
-        #[cfg(any(target_os = "netbsd", target_os = "freebsd"))]
+        /// FIXME: not present in libc for FreeBSD
+        #[cfg(target_os = "netbsd")]
         #[cfg_attr(docsrs, doc(cfg(all())))]
         MAP_ALIGNMENT_SHIFT;
         /// Mask to get the page alignment (as `(flags & align mask) >> align shift`)
-        #[cfg(any(target_os = "netbsd", target_os = "freebsd"))]
+        #[cfg(target_os = "netbsd")]
+        /// FIXME: not present in libc for FreeBSD
         #[cfg_attr(docsrs, doc(cfg(all())))]
         MAP_ALIGNMENT_MASK;
     }
@@ -643,7 +645,17 @@ pub fn shm_unlink<P: ?Sized + NixPath>(name: &P) -> Result<()> {
 /// For more information, see [`mmap(2)`].
 ///
 /// [`mmap(2)`]: https://man.freebsd.org/cgi/man.cgi?mmap(2)
-#[cfg(any(target_os = "netbsd", target_os = "freebsd"))]
+#[cfg(target_os = "netbsd")]
 pub const fn map_aligned(v: u32) -> u32 {
     v << MapFlags::MAP_ALIGNMENT_SHIFT.bits()
 }
+
+/// Handy call to get the alignment set by `map_aligned`.
+///
+/// For more information, see [`mmap(2)`].
+///
+/// [`mmap(2)`]: https://man.freebsd.org/cgi/man.cgi?mmap(2)
+#[cfg(target_os = "netbsd")]
+pub const fn map_alignment(flags: u32) -> u32 {
+    (flags & MapFlags::MAP_ALIGNMENT_MASK.bits() as u32) >> MapFlags::MAP_ALIGNMENT_SHIFT.bits()
+}

test/sys/test_mman.rs

@@ -120,3 +120,14 @@ fn test_mremap_shrink() {
     // The first KB should still be accessible and have the old data in it.
     assert_eq!(slice[ONE_K - 1], 0xFF);
 }
+
+#[test]
+#[cfg(target_os = "netbsd")]
+pub fn test_map_aligned() {
+    use nix::sys::mman::{map_aligned, map_alignment};
+
+    let aligned = map_aligned(16);
+    let flags = libc::MAP_PRIVATE as u32 | libc::MAP_ANONYMOUS as u32 | aligned;
+    assert_eq!(aligned, libc::MAP_ALIGNED(16) as u32);
+    assert_eq!(map_alignment(flags), 16);
+}