Merge #1439

1439: Add sendfile64 r=asomers a=tdryer

`sendfile64` is a Linux-specific call with a wider type for the `offset` argument than `sendfile`.

This is largely a copy of the existing `sendfile` function and associated test.

Co-authored-by: Tom Dryer <tomdryer.com@gmail.com>

Author: bors[bot]

CHANGELOG.md

@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ### Added
 - Added TIMESTAMPNS support for linux
   (#[1402](https://github.com/nix-rust/nix/pull/1402))
+- Added `sendfile64` (#[1439](https://github.com/nix-rust/nix/pull/1439))
 
 ### Changed
 - Made `forkpty` unsafe, like `fork`

src/sys/sendfile.rs

@@ -33,6 +33,32 @@ pub fn sendfile(
     Errno::result(ret).map(|r| r as usize)
 }
 
+/// Copy up to `count` bytes to `out_fd` from `in_fd` starting at `offset`.
+///
+/// Returns a `Result` with the number of bytes written.
+///
+/// If `offset` is `None`, `sendfile` will begin reading at the current offset of `in_fd`and will
+/// update the offset of `in_fd`. If `offset` is `Some`, `sendfile` will begin at the specified
+/// offset and will not update the offset of `in_fd`. Instead, it will mutate `offset` to point to
+/// the byte after the last byte copied.
+///
+/// `in_fd` must support `mmap`-like operations and therefore cannot be a socket.
+///
+/// For more information, see [the sendfile(2) man page.](https://man7.org/linux/man-pages/man2/sendfile.2.html)
+#[cfg(target_os = "linux")]
+pub fn sendfile64(
+    out_fd: RawFd,
+    in_fd: RawFd,
+    offset: Option<&mut libc::off64_t>,
+    count: usize,
+) -> Result<usize> {
+    let offset = offset
+        .map(|offset| offset as *mut _)
+        .unwrap_or(ptr::null_mut());
+    let ret = unsafe { libc::sendfile64(out_fd, in_fd, offset, count) };
+    Errno::result(ret).map(|r| r as usize)
+}
+
 cfg_if! {
     if #[cfg(any(target_os = "freebsd",
                  target_os = "ios",

test/test_sendfile.rs

@@ -36,6 +36,28 @@ fn test_sendfile_linux() {
     close(wr).unwrap();
 }
 
+#[cfg(target_os = "linux")]
+#[test]
+fn test_sendfile64_linux() {
+    const CONTENTS: &[u8] = b"abcdef123456";
+    let mut tmp = tempfile().unwrap();
+    tmp.write_all(CONTENTS).unwrap();
+
+    let (rd, wr) = pipe().unwrap();
+    let mut offset: libc::off64_t = 5;
+    let res = sendfile64(wr, tmp.as_raw_fd(), Some(&mut offset), 2).unwrap();
+
+    assert_eq!(2, res);
+
+    let mut buf = [0u8; 1024];
+    assert_eq!(2, read(rd, &mut buf).unwrap());
+    assert_eq!(b"f1", &buf[0..2]);
+    assert_eq!(7, offset);
+
+    close(rd).unwrap();
+    close(wr).unwrap();
+}
+
 #[cfg(target_os = "freebsd")]
 #[test]
 fn test_sendfile_freebsd() {