windows: reimplement uv_fs_stat using NT syscalls

This improves the output of uv_fs_stat:
  * `st_ctime` now contains the change time, not the creation time.
  * `st_ino` is now filled in with an fs-specific unique number.
  * `st_dev` is set to the serial number of the containing file system.
  * `st_blocks` now gets set.
  * `st_blksize` is no longer zero, but set to a reasonable default.

src/win/fs.c

@@ -241,7 +241,7 @@ static int is_path_dir(const WCHAR* path) {
 
 
 INLINE static int fs__readlink_handle(HANDLE handle, char** target_ptr,
-    int64_t* target_len_ptr) {
+    uint64_t* target_len_ptr) {
   char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
   REPARSE_DATA_BUFFER* reparse_data = (REPARSE_DATA_BUFFER*) buffer;
   WCHAR *w_target;
@@ -809,56 +809,117 @@ void fs__readdir(uv_fs_t* req) {
 
 
 INLINE static int fs__stat_handle(HANDLE handle, uv_stat_t* statbuf) {
-  BY_HANDLE_FILE_INFORMATION info;
+  FILE_ALL_INFORMATION file_info;
+  FILE_FS_VOLUME_INFORMATION volume_info;
+  NTSTATUS nt_status;
+  IO_STATUS_BLOCK io_status;
 
-  if (!GetFileInformationByHandle(handle, &info)) {
+  nt_status = pNtQueryInformationFile(handle,
+                                      &io_status,
+                                      &file_info,
+                                      sizeof file_info,
+                                      FileAllInformation);
+
+  /* Buffer overflow (a warning status code) is expected here. */
+  if (NT_ERROR(nt_status)) {
+    SetLastError(pRtlNtStatusToDosError(nt_status));
     return -1;
   }
 
-  /* TODO: set st_dev, st_rdev and st_ino to something meaningful. */
-  statbuf->st_ino = 0;
-  statbuf->st_dev = 0;
-  statbuf->st_rdev = 0;
+  nt_status = pNtQueryVolumeInformationFile(handle,
+                                            &io_status,
+                                            &volume_info,
+                                            sizeof volume_info,
+                                            FileFsVolumeInformation);
 
-  statbuf->st_gid = 0;
-  statbuf->st_uid = 0;
+  /* Buffer overflow (a warning status code) is expected here. */
+  if (NT_ERROR(nt_status)) {
+    SetLastError(pRtlNtStatusToDosError(nt_status));
+    return -1;
+  }
 
+  /* Todo: st_mode should probably always be 0666 for everyone. We might also
+   * want to report 0777 if the file is a .exe or a directory.
+   *
+   * Currently it's based on whether the 'readonly' attribute is set, which
+   * makes little sense because the semantics are so different: the 'read-only'
+   * flag is just a way for a user to protect against accidental deleteion, and
+   * serves no security purpose. Windows uses ACLs for that.
+   *
+   * Also people now use uv_fs_chmod() to take away the writable bit for good
+   * reasons. Windows however just makes the file read-only, which makes it
+   * impossible to delete the file afterwards, since read-only files can't be
+   * deleted.
+   *
+   * IOW it's all just a clusterfuck and we should think of something that
+   * makes slighty more sense.
+   *
+   * And uv_fs_chmod should probably just fail on windows or be a total no-op.
+   * There's nothing sensible it can do anyway.
+   */
   statbuf->st_mode = 0;
 
-  statbuf->st_blksize = 0;
-  statbuf->st_blocks = 0;
-
-  statbuf->st_flags = 0;
-  statbuf->st_gen = 0;
-
-  if (info.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
-    if (fs__readlink_handle(handle, NULL, &statbuf->st_size) != 0) {
-      return -1;
-    }
+  if (file_info.BasicInformation.FileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
     statbuf->st_mode |= S_IFLNK;
-  } else if (info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
+    if (fs__readlink_handle(handle, NULL, &statbuf->st_size) != 0)
+      return -1;
+
+  } else if (file_info.BasicInformation.FileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
     statbuf->st_mode |= _S_IFDIR;
     statbuf->st_size = 0;
+
   } else {
     statbuf->st_mode |= _S_IFREG;
-    statbuf->st_size = ((int64_t) info.nFileSizeHigh << 32) +
-                        (int64_t) info.nFileSizeLow;
+    statbuf->st_size = file_info.StandardInformation.EndOfFile.QuadPart;
   }
 
-  if (info.dwFileAttributes & FILE_ATTRIBUTE_READONLY) {
-    statbuf->st_mode |= (_S_IREAD + (_S_IREAD >> 3) + (_S_IREAD >> 6));
-  } else {
-    statbuf->st_mode |= ((_S_IREAD|_S_IWRITE) + ((_S_IREAD|_S_IWRITE) >> 3) +
-      ((_S_IREAD|_S_IWRITE) >> 6));
-  }
+  if (file_info.BasicInformation.FileAttributes & FILE_ATTRIBUTE_READONLY)
+    statbuf->st_mode |= _S_IREAD | (_S_IREAD >> 3) | (_S_IREAD >> 6);
+  else
+    statbuf->st_mode |= (_S_IREAD | _S_IWRITE) | ((_S_IREAD | _S_IWRITE) >> 3) |
+                        ((_S_IREAD | _S_IWRITE) >> 6);
+
+  FILETIME_TO_TIMESPEC(statbuf->st_atim, file_info.BasicInformation.LastAccessTime);
+  FILETIME_TO_TIMESPEC(statbuf->st_ctim, file_info.BasicInformation.ChangeTime);
+  FILETIME_TO_TIMESPEC(statbuf->st_mtim, file_info.BasicInformation.LastWriteTime);
+  FILETIME_TO_TIMESPEC(statbuf->st_birthtim, file_info.BasicInformation.CreationTime);
+
+  statbuf->st_ino = file_info.InternalInformation.IndexNumber.QuadPart;
+
+  /* st_blocks contains the on-disk allocation size in 512-byte units. */
+  statbuf->st_blocks =
+      file_info.StandardInformation.AllocationSize.QuadPart >> 9ULL;
+
+  statbuf->st_nlink = file_info.StandardInformation.NumberOfLinks;
 
-  FILETIME_TO_TIMESPEC(statbuf->st_mtim, info.ftLastWriteTime);
-  FILETIME_TO_TIMESPEC(statbuf->st_atim, info.ftLastAccessTime);
-  FILETIME_TO_TIMESPEC(statbuf->st_ctim, info.ftCreationTime);
-  FILETIME_TO_TIMESPEC(statbuf->st_birthtim, info.ftCreationTime);
+  statbuf->st_dev = volume_info.VolumeSerialNumber;
 
-  statbuf->st_nlink = (info.nNumberOfLinks <= SHRT_MAX) ?
-                      (short) info.nNumberOfLinks : SHRT_MAX;
+  /* The st_blksize is supposed to be the 'optimal' number of bytes for reading
+   * and writing to the disk. That is, for any definition of 'optimal' - it's
+   * supposed to at least avoid read-update-write behavior when writing to the
+   * disk.
+   *
+   * However nobody knows this and even fewer people actually use this value,
+   * and in order to fill it out we'd have to make another syscall to query the
+   * volume for FILE_FS_SECTOR_SIZE_INFORMATION.
+   *
+   * Therefore we'll just report a sensible value that's quite commonly okay
+   * on modern hardware.
+   */
+  statbuf->st_blksize = 2048;
+
+  /* Todo: set st_flags to something meaningful. Also provide a wrapper for
+   * chattr(2).
+   */
+  statbuf->st_flags = 0;
+
+  /* Windows has nothing sensible to say about these values, so they'll just
+   * remain empty.
+   */
+  statbuf->st_gid = 0;
+  statbuf->st_uid = 0;
+  statbuf->st_rdev = 0;
+  statbuf->st_gen = 0;
 
   return 0;
 }