From 056c1f964f55adedc17f8d7bddef1f48c73852c7 Mon Sep 17 00:00:00 2001
From: Helmut Grohne <helmut@subdivi.de>
Date: Fri, 17 May 2024 10:54:40 +0200
Subject: add a splice syscall wrapper

---
 linuxnamespaces/syscalls.py | 52 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/linuxnamespaces/syscalls.py b/linuxnamespaces/syscalls.py
index 2a35a69..11800c6 100644
--- a/linuxnamespaces/syscalls.py
+++ b/linuxnamespaces/syscalls.py
@@ -352,6 +352,16 @@ class PrctlOption(enum.IntEnum):
     PR_CAP_AMBIENT = 47
 
 
+class SpliceFlags(enum.IntFlag):
+    """This value may be supplied to splice(2) as flags."""
+
+    NONE = 0
+    MOVE = 1
+    NONBLOCK = 2
+    MORE = 4
+    GIFT = 8
+
+
 class UmountFlags(enum.IntFlag):
     """This value may be supplied to umount2(2) as flags."""
 
@@ -690,6 +700,48 @@ def setns(fd: int, nstype: CloneFlags = CloneFlags.NONE) -> None:
     call_libc("setns", fd, int(nstype))
 
 
+@dataclasses.dataclass
+class SpliceResult:
+    """Return type for splice(2) capturing out arguments."""
+
+    copied: int
+    off_int: int | None
+    off_out: int | None
+
+
+def splice(
+    fd_in: int,
+    off_in: int | None,
+    fd_out: int,
+    off_out: int | None,
+    length: int,
+    flags: SpliceFlags = SpliceFlags.NONE,
+) -> SpliceResult:
+    """Python wrapper for splice(2). Unlike the syscall, the offset arguments
+    are not output arguments. Instead, they're returned as SpliceResult.
+    """
+    if fd_in < 0 or fd_out < 0:
+        raise ValueError("invalid file descriptor")
+    if off_in is None:
+        p_off_in = None
+    else:
+        c_off_in = ctypes.c_int64(off_in)
+        p_off_in = ctypes.byref(c_off_in)
+    if off_out is None:
+        p_off_out = None
+    else:
+        c_off_out = ctypes.c_int64(off_out)
+        p_off_out = ctypes.byref(c_off_out)
+    ret = call_libc(
+        "splice", fd_in, p_off_in, fd_out, p_off_out, length, int(flags)
+    )
+    return SpliceResult(
+        ret,
+        None if off_in is None else c_off_in.value,
+        None if off_out is None else c_off_out.value,
+    )
+
+
 def umount(
     path: PathConvertible, flags: UmountFlags = UmountFlags.NONE
 ) -> None:
-- 
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