Rename `libmount` to `filesystem`

1 files changed, 88 insertions, 0 deletions

diff --git a/snekbox/filesystem.py b/snekbox/filesystem.py
new file mode 100644
index 0000000..0cdfbf5
--- /dev/null
+++ b/snekbox/filesystem.py
@@ -0,0 +1,88 @@
+"""Mounts and unmounts filesystems."""
+from __future__ import annotations
+
+import ctypes
+import os
+from ctypes.util import find_library
+from enum import IntEnum
+from pathlib import Path
+
+__all__ = ("mount", "unmount", "Size", "UnmountFlags")
+
+libc = ctypes.CDLL(find_library("c"), use_errno=True)
+libc.mount.argtypes = (
+    ctypes.c_char_p,
+    ctypes.c_char_p,
+    ctypes.c_char_p,
+    ctypes.c_ulong,
+    ctypes.c_char_p,
+)
+libc.umount2.argtypes = (ctypes.c_char_p, ctypes.c_int)
+
+
+class Size(int):
+    """Size in bytes."""
+
+    @classmethod
+    def from_mb(cls, mb: int) -> Size:
+        """Create a Size from mebibytes."""
+        return cls(mb * 1024 * 1024)
+
+
+class UnmountFlags(IntEnum):
+    """Flags for umount2."""
+
+    MNT_FORCE = 1
+    MNT_DETACH = 2
+    MNT_EXPIRE = 4
+    UMOUNT_NOFOLLOW = 8
+
+
+def mount(source: Path | str, target: Path | str, fs: str, **options: str | int) -> None:
+    """
+    Mount a filesystem.
+
+    https://man7.org/linux/man-pages/man8/mount.8.html
+
+    Args:
+        source: Source directory or device.
+        target: Target directory.
+        fs: Filesystem type.
+        **options: Mount options.
+
+    Raises:
+        OSError: On any mount error.
+    """
+    if Path(target).is_mount():
+        raise OSError(f"{target} is already a mount point")
+
+    kwargs = " ".join(f"{key}={value}" for key, value in options.items())
+
+    result: int = libc.mount(
+        str(source).encode(), str(target).encode(), fs.encode(), 0, kwargs.encode()
+    )
+    if result < 0:
+        errno = ctypes.get_errno()
+        raise OSError(errno, f"Error mounting {target}: {os.strerror(errno)}")
+
+
+def unmount(target: Path | str, flags: UnmountFlags | int = UnmountFlags.MNT_DETACH) -> None:
+    """
+    Unmount a filesystem.
+
+    https://man7.org/linux/man-pages/man2/umount.2.html
+
+    Args:
+        target: Target directory.
+        flags: Unmount flags.
+
+    Raises:
+        OSError: On any unmount error.
+    """
+    if not Path(target).is_mount():
+        raise OSError(f"{target} is not a mount point")
+
+    result: int = libc.umount2(str(target).encode(), int(flags))
+    if result < 0:
+        errno = ctypes.get_errno()
+        raise OSError(errno, f"Error unmounting {target}: {os.strerror(errno)}")