From 0f19012b1ce57301e6ede3de7bfb4f45d8125706 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81rni=20Dagur?= <arnidg@protonmail.ch>
Date: Tue, 11 Jun 2019 22:44:11 +0000
Subject: Implement `copy_file_range()`

---
 src/fcntl.rs | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 65 insertions(+), 8 deletions(-)

(limited to 'src/fcntl.rs')

diff --git a/src/fcntl.rs b/src/fcntl.rs
index 6da62d87..3d932a53 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -7,6 +7,8 @@ use std::os::unix::io::RawFd;
 use std::ffi::OsStr;
 use std::os::unix::ffi::OsStrExt;
 
+#[cfg(any(target_os = "android", target_os = "linux"))]
+use std::ptr; // For splice and copy_file_range
 #[cfg(any(target_os = "android", target_os = "linux"))]
 use sys::uio::IoVec;  // For vmsplice
 
@@ -325,15 +327,70 @@ libc_bitflags! {
     }
 }
 
+/// Copy a range of data from one file to another
+///
+/// The `copy_file_range` system call performs an in-kernel copy between
+/// file descriptors `fd_in` and `fd_out` without the additional cost of
+/// transferring data from the kernel to user space and then back into the
+/// kernel. It copies up to `len` bytes of data from file descriptor `fd_in` to
+/// file descriptor `fd_out`, overwriting any data that exists within the
+/// requested range of the target file.
+///
+/// If the `off_in` and/or `off_out` arguments are used, the values
+/// will be mutated to reflect the new position within the file after
+/// copying. If they are not used, the relevant filedescriptors will be seeked
+/// to the new position.
+///
+/// On successful completion the number of bytes actually copied will be
+/// returned.
+#[cfg(any(target_os = "android", target_os = "linux"))]
+pub fn copy_file_range(
+    fd_in: RawFd,
+    off_in: Option<&mut libc::loff_t>,
+    fd_out: RawFd,
+    off_out: Option<&mut libc::loff_t>,
+    len: usize,
+) -> Result<usize> {
+    let off_in = off_in
+        .map(|offset| offset as *mut libc::loff_t)
+        .unwrap_or(ptr::null_mut());
+    let off_out = off_out
+        .map(|offset| offset as *mut libc::loff_t)
+        .unwrap_or(ptr::null_mut());
+
+    let ret = unsafe {
+        libc::syscall(
+            libc::SYS_copy_file_range,
+            fd_in,
+            off_in,
+            fd_out,
+            off_out,
+            len,
+            0,
+        )
+    };
+    Errno::result(ret).map(|r| r as usize)
+}
+
 #[cfg(any(target_os = "linux", target_os = "android"))]
-pub fn splice(fd_in: RawFd, off_in: Option<&mut libc::loff_t>,
-          fd_out: RawFd, off_out: Option<&mut libc::loff_t>,
-          len: usize, flags: SpliceFFlags) -> Result<usize> {
-    use std::ptr;
-    let off_in = off_in.map(|offset| offset as *mut _).unwrap_or(ptr::null_mut());
-    let off_out = off_out.map(|offset| offset as *mut _).unwrap_or(ptr::null_mut());
-
-    let ret = unsafe { libc::splice(fd_in, off_in, fd_out, off_out, len, flags.bits()) };
+pub fn splice(
+    fd_in: RawFd,
+    off_in: Option<&mut libc::loff_t>,
+    fd_out: RawFd,
+    off_out: Option<&mut libc::loff_t>,
+    len: usize,
+    flags: SpliceFFlags,
+) -> Result<usize> {
+    let off_in = off_in
+        .map(|offset| offset as *mut libc::loff_t)
+        .unwrap_or(ptr::null_mut());
+    let off_out = off_out
+        .map(|offset| offset as *mut libc::loff_t)
+        .unwrap_or(ptr::null_mut());
+
+    let ret = unsafe {
+        libc::splice(fd_in, off_in, fd_out, off_out, len, flags.bits())
+    };
     Errno::result(ret).map(|r| r as usize)
 }
 
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