fcntl: Support getting and setting pipe size on Linux

Author: kamalmarhubi

CHANGELOG.md

@@ -44,6 +44,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#503](https://github.com/nix-rust/nix/pull/503))
 - Added `ppoll` in `::nix::poll`
   ([#520](https://github.com/nix-rust/nix/pull/520))
+- Added getting and setting pipe size with fcntl on Linux
+  ([#TODO](https://github.com/nix-rust/nix/pull/TODO)
 
 ### Changed
 - `::nix::sys::termios::{cfgetispeed, cfsetispeed, cfgetospeed, cfsetospeed}` 

src/fcntl.rs

@@ -48,6 +48,10 @@ pub enum FcntlArg<'a> {
     F_GET_SEALS,
     #[cfg(any(target_os = "macos", target_os = "ios"))]
     F_FULLFSYNC,
+    #[cfg(any(target_os = "linux", target_os = "android"))]
+    F_GETPIPE_SZ,
+    #[cfg(any(target_os = "linux", target_os = "android"))]
+    F_SETPIPE_SZ(libc::c_int),
 
     // TODO: Rest of flags
 }
@@ -74,6 +78,10 @@ pub fn fcntl(fd: RawFd, arg: FcntlArg) -> Result<c_int> {
             #[cfg(any(target_os = "macos", target_os = "ios"))]
             F_FULLFSYNC => libc::fcntl(fd, libc::F_FULLFSYNC),
             #[cfg(any(target_os = "linux", target_os = "android"))]
+            F_GETPIPE_SZ => libc::fcntl(fd, libc::F_GETPIPE_SZ),
+            #[cfg(any(target_os = "linux", target_os = "android"))]
+            F_SETPIPE_SZ(size) => libc::fcntl(fd, libc::F_SETPIPE_SZ, size),
+            #[cfg(any(target_os = "linux", target_os = "android"))]
             _ => unimplemented!()
         }
     };