Method openParent

Marlin/src/sd/SdBaseFile.cpp:1187–1230

* Open a directory's parent directory. * * \param[in] dir Parent of this directory will be opened. Must not be root. * * \return true for success, false for failure. */

 * \return true for success, false for failure.
 */
bool SdBaseFile::openParent(SdBaseFile *dir) {
  dir_t entry;
  SdBaseFile file;
  uint32_t c;
  uint32_t cluster;
  uint32_t lbn;
  // error if already open or dir is root or dir is not a directory
  if (isOpen() || !dir || dir->isRoot() || !dir->isDir()) return false;
  vol_ = dir->vol_;
  // position to '..'
  if (!dir->seekSet(32)) return false;
  // read '..' entry
  if (dir->read(&entry, sizeof(entry)) != 32) return false;
  // verify it is '..'
  if (entry.name[0] != '.' || entry.name[1] != '.') return false;
  // start cluster for '..'
  cluster = entry.firstClusterLow;
  cluster |= (uint32_t)entry.firstClusterHigh << 16;
  if (cluster == 0) return openRoot(vol_);
  // start block for '..'
  lbn = vol_->clusterStartBlock(cluster);
  // first block of parent dir
  if (!vol_->cacheRawBlock(lbn, SdVolume::CACHE_FOR_READ)) return false;

  dir_t *p = &vol_->cacheBuffer_.dir[1];
  // verify name for '../..'
  if (p->name[0] != '.' || p->name[1] != '.') return false;
  // '..' is pointer to first cluster of parent. open '../..' to find parent
  if (p->firstClusterHigh == 0 && p->firstClusterLow == 0) {
    if (!file.openRoot(dir->volume())) return false;
  }
  else if (!file.openCachedEntry(1, O_READ))
    return false;

  // search for parent in '../..'
  do {
    if (file.readDir(&entry, nullptr) != 32) return false;
    c = entry.firstClusterLow;
    c |= (uint32_t)entry.firstClusterHigh << 16;
  } while (c != cluster);

  // open parent
  return open(&file, file.curPosition() / 32 - 1, O_READ);
}
#endif

/**