eio_windows: initial filesystem implementation

Author: patricoferris

lib_eio_windows/dune

@@ -1,7 +1,7 @@
 (library
  (name eio_windows)
  (public_name eio_windows)
- (library_flags :standard -ccopt -lbcrypt)
+ (library_flags :standard -ccopt -lbcrypt -ccopt -lntdll)
  (enabled_if (= %{os_type} "Win32"))
  (foreign_stubs
   (language c)

lib_eio_windows/eio_windows.ml

@@ -31,8 +31,8 @@ let run main =
     method mono_clock = Time.mono_clock
     method net = Net.v
     method domain_mgr = Domain_mgr.v
-    method cwd = failwith "file-system operations not supported on Windows yet"
-    method fs = failwith "file-system operations not supported on Windows yet"
+    method cwd = ((Fs.cwd, "") :> Eio.Fs.dir Eio.Path.t)
+    method fs = ((Fs.fs, "") :> Eio.Fs.dir Eio.Path.t)
     method process_mgr = failwith "process operations not supported on Windows yet"
     method secure_random = Flow.secure_random
   end

lib_eio_windows/eio_windows_stubs.c

@@ -11,12 +11,29 @@
 #include <assert.h>
 #include <ntstatus.h>
 #include <bcrypt.h>
+#include <winternl.h>
+#include <ntdef.h>
+
+typedef ULONG (__stdcall *pNtCreateFile)(
+   PHANDLE FileHandle,
+   ULONG DesiredAccess,
+   PVOID ObjectAttributes,
+   PVOID IoStatusBlock,
+   PLARGE_INTEGER AllocationSize,
+   ULONG FileAttributes,
+   ULONG ShareAccess,
+   ULONG CreateDisposition,
+   ULONG CreateOptions,
+   PVOID EaBuffer,
+   ULONG EaLength
+ );
 
 #include <caml/mlvalues.h>
 #include <caml/memory.h>
 #include <caml/alloc.h>
 #include <caml/unixsupport.h>
 #include <caml/bigarray.h>
+#include <caml/osdeps.h>
 
 #ifdef ARCH_SIXTYFOUR
 #define Int63_val(v) Long_val(v)
@@ -64,19 +81,170 @@ CAMLprim value caml_eio_windows_pwritev(value v_fd, value v_bufs, value v_offset
   uerror("pwritev is not supported on windows yet", Nothing);
 }
 
-CAMLprim value caml_eio_windows_openat(value v_dirfd, value v_pathname, value v_flags, value v_mode)
-{
-  uerror("openat is not supported on windows yet", Nothing);
+// File-system operations
+
+// No follow
+void no_follow(HANDLE h) {
+  BY_HANDLE_FILE_INFORMATION b;
+
+  if (!GetFileInformationByHandle(h, &b)) {
+    caml_win32_maperr(GetLastError());
+    uerror("nofollow", Nothing);
+  }
+
+  if (b.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+    CloseHandle(h);
+    caml_unix_error(ELOOP, "nofollow", Nothing);
+  }
 }
 
-CAMLprim value caml_eio_windows_mkdirat(value v_fd, value v_path, value v_perm)
+// We recreate an openat like function using NtCreateFile
+CAMLprim value caml_eio_windows_openat(value v_dirfd, value v_nofollow, value v_pathname, value v_desired_access, value v_create_disposition, value v_create_options)
 {
-  uerror("mkdirat is not supported on windows yet", Nothing);
+  CAMLparam2(v_dirfd, v_pathname);
+  HANDLE h, dir;
+  OBJECT_ATTRIBUTES obj_attr;
+  IO_STATUS_BLOCK io_status;
+  wchar_t *pathname;
+  UNICODE_STRING relative;
+  NTSTATUS r;
+
+  // Not sure what the overhead of this is, but it allows us to have low-level control
+  // over file creation. In particular, we can specify the HANDLE to the parent directory
+  // of a relative path a la openat.
+  pNtCreateFile NtCreatefile = (pNtCreateFile)GetProcAddress(GetModuleHandle("ntdll.dll"), "NtCreateFile");
+  caml_unix_check_path(v_pathname, "openat");
+  pathname = caml_stat_strdup_to_utf16(String_val(v_pathname));
+  RtlInitUnicodeString(&relative, pathname);
+
+  // If NULL the filepath has to be absolute
+  if (Is_some(v_dirfd)) {
+    dir = Handle_val(Field(v_dirfd, 0));
+  } else {
+    dir = NULL;
+  }
+
+  // Initialise object attributes, passing in the root directory FD
+  InitializeObjectAttributes(
+    &obj_attr,
+    &relative,
+    OBJ_CASE_INSENSITIVE, // TODO: Double-check what flags need to be passed at this point.
+    dir,
+    NULL
+  );
+
+  // Create the file
+  r = NtCreatefile(
+    &h,
+    Int_val(v_desired_access) | FILE_READ_ATTRIBUTES,
+    &obj_attr,
+    &io_status,
+    0, // Allocation size
+    FILE_ATTRIBUTE_NORMAL, // TODO: Could check flags to see if we can do READONLY here a la OCaml
+    (FILE_SHARE_READ | FILE_SHARE_WRITE),
+    Int_val(v_create_disposition),
+    ( 
+       FILE_SYNCHRONOUS_IO_NONALERT
+      | FILE_OPEN_FOR_BACKUP_INTENT
+      | (Bool_val(v_nofollow) ? FILE_FLAG_OPEN_REPARSE_POINT : Int_val(v_create_options))),
+    NULL, // Extended attribute buffer
+    0     // Extended attribute buffer length
+  );
+
+  // Free the allocated pathname
+  caml_stat_free(pathname);
+
+  if (h == INVALID_HANDLE_VALUE) {
+    caml_win32_maperr(RtlNtStatusToDosError(r));
+    uerror("openat handle", v_pathname);
+  }
+
+   if (!NT_SUCCESS(r)) {
+    caml_win32_maperr(RtlNtStatusToDosError(r));
+    uerror("openat", Nothing);
+  }
+
+  // No follow check -- Windows doesn't actually have that ability
+  // so we have to do it after the fact. This will raise if a symbolic
+  // link is encountered and will close the handle.
+  if (Bool_val(v_nofollow)) {
+    no_follow(h);
+  }
+  
+  CAMLreturn(caml_win32_alloc_handle(h));
+}
+
+value caml_eio_windows_openat_bytes(value* values, int argc) {
+    return caml_eio_windows_openat(values[0], values[1], values[2], values[3], values[4], values[5]);
 }
 
-CAMLprim value caml_eio_windows_unlinkat(value v_fd, value v_path, value v_dir)
+CAMLprim value caml_eio_windows_unlinkat(value v_dirfd, value v_pathname, value v_dir)
 {
-  uerror("unlinkat is not supported on windows yet", Nothing);
+  CAMLparam2(v_dirfd, v_pathname);
+  HANDLE h, dir;
+  OBJECT_ATTRIBUTES obj_attr;
+  IO_STATUS_BLOCK io_status;
+  wchar_t *pathname;
+  UNICODE_STRING relative;
+  NTSTATUS r;
+
+  // Not sure what the overhead of this is, but it allows us to have low-level control
+  // over file creation. In particular, we can specify the HANDLE to the parent directory
+  // of a relative path a la openat.
+  pNtCreateFile NtCreatefile = (pNtCreateFile)GetProcAddress(GetModuleHandle("ntdll.dll"), "NtCreateFile");
+  caml_unix_check_path(v_pathname, "openat");
+  pathname = caml_stat_strdup_to_utf16(String_val(v_pathname));
+  RtlInitUnicodeString(&relative, pathname);
+
+  // If NULL the filepath has to be absolute
+  if (Is_some(v_dirfd)) {
+    dir = Handle_val(Field(v_dirfd, 0));
+  } else {
+    dir = NULL;
+  }
+
+  // Initialise object attributes, passing in the root directory FD
+  InitializeObjectAttributes(
+    &obj_attr,
+    &relative,
+    OBJ_CASE_INSENSITIVE, // TODO: Double-check what flags need to be passed at this point.
+    dir,
+    NULL
+  );
+
+  // Create the file
+  r = NtCreatefile(
+    &h,
+    (SYNCHRONIZE | DELETE),
+    &obj_attr,
+    &io_status,
+    0, // Allocation size
+    FILE_ATTRIBUTE_NORMAL, // TODO: Could check flags to see if we can do READONLY here a la OCaml
+    (FILE_SHARE_DELETE),
+    FILE_OPEN,
+    ((Bool_val(v_dir) ? FILE_DIRECTORY_FILE : FILE_NON_DIRECTORY_FILE) | FILE_SYNCHRONOUS_IO_NONALERT | FILE_DELETE_ON_CLOSE),
+    NULL, // Extended attribute buffer
+    0     // Extended attribute buffer length
+  );
+
+  // Free the allocated pathname
+  caml_stat_free(pathname);
+
+  if (h == INVALID_HANDLE_VALUE) {
+    caml_win32_maperr(RtlNtStatusToDosError(r));
+    uerror("openat", v_pathname);
+  }
+
+  if (!NT_SUCCESS(r)) {
+    caml_win32_maperr(RtlNtStatusToDosError(r));
+    uerror("openat", Nothing);
+  }
+
+  // Now close the file to delete it
+  BOOL closed;
+  closed = CloseHandle(h);
+  
+  CAMLreturn(Val_unit);
 }
 
 CAMLprim value caml_eio_windows_renameat(value v_old_fd, value v_old_path, value v_new_fd, value v_new_path)