Implement getattrlist for improved CoW detection

opencore_legacy_patcher/volume/properties.py

@@ -0,0 +1,110 @@
+"""
+properties.py: Query volume properties for a given path using macOS's getattrlist.
+"""
+
+import ctypes
+
+
+class attrreference_t(ctypes.Structure):
+    _fields_ = [
+        ("attr_dataoffset", ctypes.c_int32),
+        ("attr_length",     ctypes.c_uint32)
+    ]
+
+class attrlist_t(ctypes.Structure):
+    _fields_ = [
+        ("bitmapcount", ctypes.c_ushort),
+        ("reserved",    ctypes.c_uint16),
+        ("commonattr",  ctypes.c_uint),
+        ("volattr",     ctypes.c_uint),
+        ("dirattr",     ctypes.c_uint),
+        ("fileattr",    ctypes.c_uint),
+        ("forkattr",    ctypes.c_uint)
+    ]
+
+class volattrbuf(ctypes.Structure):
+    _fields_ = [
+        ("length",          ctypes.c_uint32),
+        ("mountPoint",      attrreference_t),
+        ("volCapabilities", ctypes.c_uint64),
+        ("mountPointSpace", ctypes.c_char * 1024),
+    ]
+
+
+class PathAttributes:
+
+    def __init__(self, path: str) -> None:
+        self._path = path
+        if not isinstance(self._path, str):
+            try:
+                self._path = str(self._path)
+            except:
+                raise ValueError(f"Invalid path: {path}")
+
+        _libc = ctypes.CDLL("/usr/lib/libc.dylib")
+
+        # Reference:
+        # https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getattrlist.2.html
+        try:
+            self._getattrlist = _libc.getattrlist
+        except AttributeError:
+            return
+
+        self._getattrlist.argtypes = [
+            ctypes.c_char_p,             # Path
+            ctypes.POINTER(attrlist_t),  # Attribute list
+            ctypes.c_void_p,             # Attribute buffer
+            ctypes.c_ulong,              # Attribute buffer size
+            ctypes.c_ulong               # Options
+        ]
+        self._getattrlist.restype = ctypes.c_int
+
+        # Reference:
+        # https://github.com/apple-oss-distributions/xnu/blob/xnu-10063.121.3/bsd/sys/attr.h
+        ATTR_BIT_MAP_COUNT     = 0x00000005
+        ATTR_VOL_MOUNTPOINT    = 0x00001000
+        ATTR_VOL_CAPABILITIES  = 0x00020000
+
+        attrList = attrlist_t()
+        attrList.bitmapcount = ATTR_BIT_MAP_COUNT
+        attrList.volattr     = ATTR_VOL_MOUNTPOINT | ATTR_VOL_CAPABILITIES
+
+        volAttrBuf = volattrbuf()
+
+        if self._getattrlist(self._path.encode(), ctypes.byref(attrList), ctypes.byref(volAttrBuf), ctypes.sizeof(volAttrBuf), 0) != 0:
+            return
+
+        self._volAttrBuf = volAttrBuf
+
+
+    def supports_clonefile(self) -> bool:
+        """
+        Verify if path provided supports Apple's clonefile function.
+
+        Equivalent to checking for Copy on Write support.
+        """
+        VOL_CAP_INT_CLONE = 0x00010000
+
+        if not hasattr(self, "_volAttrBuf"):
+            return False
+
+        if self._volAttrBuf.volCapabilities & VOL_CAP_INT_CLONE:
+            return True
+
+        return False
+
+
+    def mount_point(self) -> str:
+        """
+        Return mount point of path.
+        """
+
+        if not hasattr(self, "_volAttrBuf"):
+            return ""
+
+        mount_point_ptr = ctypes.cast(
+            ctypes.addressof(self._volAttrBuf.mountPoint) + self._volAttrBuf.mountPoint.attr_dataoffset,
+            ctypes.POINTER(ctypes.c_char * self._volAttrBuf.mountPoint.attr_length)
+        )
+
+        return mount_point_ptr.contents.value.decode()