From b6fc1511f0818f7cd184e62d23f13853ec7e60c0 Mon Sep 17 00:00:00 2001
From: ZipFile <zipfile.d@protonmail.com>
Date: Thu, 6 Aug 2026 15:28:14 +0000
Subject: [PATCH] wip

---
 getdents/c_common.py | 58 ++++++++++++++++++++++++++++++++++++++++++++
 getdents/cffi.py     | 45 ++++++++++++++++++++++++++++++++++
 getdents/ctypes.py   | 43 ++++++++++++++++++++++++++++++++
 3 files changed, 146 insertions(+)
 create mode 100644 getdents/c_common.py
 create mode 100644 getdents/cffi.py
 create mode 100644 getdents/ctypes.py

diff --git a/getdents/c_common.py b/getdents/c_common.py
new file mode 100644
index 0000000..4b49ed7
--- /dev/null
+++ b/getdents/c_common.py
@@ -0,0 +1,58 @@
+import errno
+import fcntl
+import os
+import struct
+from typing import Iterable
+
+DIRENT64_RECORD = struct.Struct("=QqHB")
+DIRENT64_OFFSET = DIRENT64_RECORD.size
+O_GETDENTS = os.O_DIRECTORY | os.O_RDONLY | os.O_NONBLOCK | os.O_CLOEXEC
+
+try:
+    _NAME_MAX = os.pathconf("/", "PC_NAME_MAX")
+except OSError:
+    _NAME_MAX = 255
+
+MIN_GETDENTS_BUFF_SIZE = _NAME_MAX + DIRENT64_OFFSET
+
+DirectoryEntry = tuple[int, int, str]
+
+
+def fd_is_directory(fd: int) -> bool:
+    return bool(fcntl.fcntl(fd, fcntl.F_GETFL) & os.O_DIRECTORY)
+
+
+def decode_dirent_name(raw: memoryview) -> str:
+    end = len(raw)
+
+    while end > 0 and raw[end - 1] == 0:
+        end -= 1
+
+    return os.fsdecode(raw[:end].tobytes())
+
+
+def validate(fd: int, buff_size: int) -> None:
+    if not isinstance(fd, int):
+        raise TypeError("fd must be an int")
+
+    if not isinstance(buff_size, int):
+        raise TypeError("buff_size must be an int")
+
+    if not fd_is_directory(fd):
+        raise NotADirectoryError("fd must refer to a directory")
+
+    if buff_size < os.fpathconf(fd, "PC_NAME_MAX") + DIRENT64_OFFSET:
+        raise ValueError("buff_size is too small")
+
+
+def parse(data: memoryview, nread: int) -> Iterable[DirectoryEntry]:
+    bpos = 0
+
+    while bpos < nread:
+        d_ino, _, d_reclen, d_type = DIRENT64_RECORD.unpack_from(data, bpos)
+        name_start = bpos + DIRENT64_OFFSET
+        name_end = bpos + d_reclen
+        name = decode_dirent_name(data[name_start:name_end])
+        bpos += d_reclen
+
+        yield d_ino, d_type, name
diff --git a/getdents/cffi.py b/getdents/cffi.py
new file mode 100644
index 0000000..00e856e
--- /dev/null
+++ b/getdents/cffi.py
@@ -0,0 +1,45 @@
+import os
+from typing import Iterator
+
+import cffi
+
+from .c_common import DirectoryEntry
+from .c_common import parse as _parse
+from .c_common import validate as _validate
+
+_ffi = cffi.FFI()
+_ffi.cdef(
+    """
+static const long SYS_getdents64;
+long syscall(long number, ...);
+"""
+)
+lib = _ffi.verify(
+    """
+#include <sys/syscall.h>
+"""
+)
+_libc = _ffi.dlopen(None)
+SYS_getdents64 = lib.SYS_getdents64
+
+
+def getdents_raw(fd: int, buff_size: int) -> Iterator[DirectoryEntry]:
+    _validate(fd, buff_size)
+    buff = _ffi.new("char[]", buff_size)
+
+    with memoryview(_ffi.buffer(buff, buff_size)).cast("B") as data:
+        while True:
+            nread = _libc.syscall(
+                SYS_getdents64,
+                _ffi.cast("int", fd),
+                buff,
+                _ffi.cast("int", buff_size),
+            )
+
+            if nread == 0:
+                return
+            elif nread == -1:
+                err = _ffi.errno
+                raise OSError(err, os.strerror(err))
+
+            yield from _parse(data, nread)
diff --git a/getdents/ctypes.py b/getdents/ctypes.py
new file mode 100644
index 0000000..33e62b2
--- /dev/null
+++ b/getdents/ctypes.py
@@ -0,0 +1,43 @@
+import ctypes
+import ctypes.util
+import os
+from collections.abc import Iterator
+
+import seccomp
+
+from .c_common import DirectoryEntry
+from .c_common import parse as _parse
+from .c_common import validate as _validate
+
+_libc = ctypes.CDLL(None, use_errno=True)
+_libc.syscall.argtypes = (
+    ctypes.c_long,
+    ctypes.c_int,
+    ctypes.c_void_p,
+    ctypes.c_size_t,
+)
+_libc.syscall.restype = ctypes.c_long
+SYS_getdents64 = seccomp.resolve_syscall(seccomp.Arch(), "getdents64")
+
+
+def getdents_raw(fd: int, buff_size: int) -> Iterator[DirectoryEntry]:
+    _validate(fd, buff_size)
+
+    buff = ctypes.create_string_buffer(buff_size)
+
+    with memoryview(buff).cast("B") as data:
+        while True:
+            nread = _libc.syscall(
+                SYS_getdents64,
+                fd,
+                ctypes.byref(buff),
+                buff_size,
+            )
+
+            if nread == 0:
+                return
+            elif nread == -1:
+                err = ctypes.get_errno()
+                raise OSError(err, os.strerror(err))
+
+            yield from _parse(data, nread)