support sendfile in async_copyfd

1 files changed, 37 insertions, 4 deletions

diff --git a/linuxnamespaces/__init__.py b/linuxnamespaces/__init__.py
index a39ab1d..65dfc8d 100644
--- a/linuxnamespaces/__init__.py
+++ b/linuxnamespaces/__init__.py
@@ -585,6 +585,39 @@ def unshare_user_idmap_nohelper(
     newidmaps(-1, [uidmap], [gidmap], False)
 
 
+class _AsyncFilesender:
+    bs = 65536
+
+    def __init__(self, from_fd: int, to_fd: int, count: int | None = None):
+        self.from_fd = from_fd
+        self.to_fd = to_fd
+        self.copied = 0
+        self.remain = count
+        self.loop = asyncio.get_running_loop()
+        self.fut: asyncio.Future[int] = self.loop.create_future()
+        self.loop.add_writer(self.to_fd, self.handle_write)
+
+    def handle_write(self) -> None:
+        try:
+            ret = os.sendfile(
+                self.to_fd,
+                self.from_fd,
+                None,
+                self.bs if self.remain is None else min(self.bs, self.remain),
+            )
+        except OSError as err:
+            if err.errno != errno.EAGAIN:
+                self.loop.remove_writer(self.to_fd)
+                self.fut.set_exception(err)
+        else:
+            self.copied += ret
+            if self.remain is not None:
+                self.remain -= ret
+            if ret == 0 or self.remain == 0:
+                self.loop.remove_writer(self.to_fd)
+                self.fut.set_result(self.copied)
+
+
 class _AsyncSplicer:
     bs = 65536
 
@@ -703,10 +736,10 @@ def async_copyfd(
     binary. An efficient implementation is chosen depending on the file type
     of file descriptors.
     """
-    if (
-        stat.S_ISFIFO(os.fstat(from_fd).st_mode)
-        or stat.S_ISFIFO(os.fstat(to_fd).st_mode)
-    ):
+    from_mode = os.fstat(from_fd).st_mode
+    if stat.S_ISREG(from_mode):
+        return _AsyncFilesender(from_fd, to_fd, count).fut
+    if stat.S_ISFIFO(from_mode) or stat.S_ISFIFO(os.fstat(to_fd).st_mode):
         return _AsyncSplicer(from_fd, to_fd, count).fut
     return _AsyncCopier(from_fd, to_fd, count).fut