From 66be0128ba9b984e0402a57ded0a038b4efb8e7b Mon Sep 17 00:00:00 2001
From: David CARLIER <devnexen@gmail.com>
Date: Fri, 6 Sep 2024 08:00:50 +0100
Subject: [PATCH] fcntl adding apple F_PREALLOCATE flag. (#2393)

---
 changelog/2393.added.md |  1 +
 src/fcntl.rs            | 13 +++++++++++--
 test/test_fcntl.rs      | 18 ++++++++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 changelog/2393.added.md

diff --git a/changelog/2393.added.md b/changelog/2393.added.md
new file mode 100644
index 0000000000..d0c2dd6288
--- /dev/null
+++ b/changelog/2393.added.md
@@ -0,0 +1 @@
+Add `fcntl`'s `F_PREALLOCATE` constant for Apple targets.
diff --git a/src/fcntl.rs b/src/fcntl.rs
index 7272a950c7..c104246882 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -802,7 +802,12 @@ pub enum FcntlArg<'a> {
     F_RDADVISE(libc::radvisory),
     /// Turn read ahead off/on
     #[cfg(apple_targets)]
-    F_RDAHEAD(bool)
+    F_RDAHEAD(bool),
+    /// Pre-allocate storage with different policies on fd.
+    /// Note that we want a mutable reference for the OUT
+    /// fstore_t field fst_bytesalloc.
+    #[cfg(apple_targets)]
+    F_PREALLOCATE(&'a mut libc::fstore_t),
     // TODO: Rest of flags
 }
 
@@ -919,7 +924,11 @@ pub fn fcntl<Fd: std::os::fd::AsFd>(fd: Fd, arg: FcntlArg) -> Result<c_int> {
             F_RDAHEAD(on) => {
                 let val = if on { 1 } else { 0 };
                 libc::fcntl(fd, libc::F_RDAHEAD, val)
-            }
+            },
+            #[cfg(apple_targets)]
+            F_PREALLOCATE(st) => {
+                libc::fcntl(fd, libc::F_PREALLOCATE, st)
+            },
         }
     };
 
diff --git a/test/test_fcntl.rs b/test/test_fcntl.rs
index f8eddd3cde..c273e9acfb 100644
--- a/test/test_fcntl.rs
+++ b/test/test_fcntl.rs
@@ -581,6 +581,24 @@ fn test_f_get_path() {
     );
 }
 
+#[cfg(apple_targets)]
+#[test]
+fn test_f_preallocate() {
+    use nix::fcntl::*;
+
+    let tmp = NamedTempFile::new().unwrap();
+    let mut st: libc::fstore_t = unsafe { std::mem::zeroed() };
+
+    st.fst_flags = libc::F_ALLOCATECONTIG as libc::c_uint;
+    st.fst_posmode = libc::F_PEOFPOSMODE;
+    st.fst_length = 1024;
+    let res = fcntl(tmp, FcntlArg::F_PREALLOCATE(&mut st))
+        .expect("preallocation failed");
+
+    assert_eq!(res, 0);
+    assert!(st.fst_bytesalloc > 0);
+}
+
 #[cfg(apple_targets)]
 #[test]
 fn test_f_get_path_nofirmlink() {