Method insertMove

system/lib/wasmfs/file.cpp:140–187

TODO: consider moving this to be `Backend::move` to avoid asymmetry between the source and destination directories and/or taking `Directory::Handle` arguments to prove that the directories have already been locked.

// the source and destination directories and/or taking `Directory::Handle`
// arguments to prove that the directories have already been locked.
int Directory::Handle::insertMove(const std::string& name,
                                  std::shared_ptr<File> file) {
  // Cannot insert into an unlinked directory.
  if (!getParent()) {
    return -EPERM;
  }

  // Look up the file in its old parent's cache.
  auto oldParent = file->locked().getParent();
  auto& oldCache = oldParent->dcache;
  auto oldIt = std::find_if(oldCache.begin(), oldCache.end(), [&](auto& kv) {
    return kv.second.file == file;
  });

  // TODO: Handle moving mount points correctly by only updating caches without
  // involving the backend.

  // Attempt the move.
  if (auto err = getDir()->insertMove(name, file)) {
    return err;
  }

  if (oldIt != oldCache.end()) {
    // Do the move and update the caches.
    auto [oldName, entry] = *oldIt;
    assert(oldName.size());
    // Update parent pointers and caches to reflect the successful move.
    oldCache.erase(oldIt);
    auto& newCache = getDir()->dcache;
    auto [it, inserted] = newCache.insert({name, entry});
    if (!inserted) {
      // Update and overwrite the overwritten file.
      it->second.file->locked().setParent(nullptr);
      it->second = entry;
    }
  } else {
    // This backend doesn't use the dcache.
    assert(getDir()->maintainsFileIdentity());
  }

  file->locked().setParent(getDir());

  // TODO: Moving mount points probably shouldn't update the mtime.
  oldParent->locked().updateMTime();
  updateMTime();

  return 0;
}

int Directory::Handle::removeChild(const std::string& name) {
  auto& dcache = getDir()->dcache;