Class AddressFilter

xds/src/main/java/io/grpc/xds/AddressFilter.java:30–99

import javax.annotation.Nullable;

final class AddressFilter {
  @ResolutionResultAttr
  static final Attributes.Key<PathChain> PATH_CHAIN_KEY =
      Attributes.Key.create("io.grpc.xds.AddressFilter.PATH_CHAIN_KEY");

  // Prevent instantiation.
  private AddressFilter() {}

  /**
   * Returns a new EquivalentAddressGroup by setting a path filter to the given
   * EquivalentAddressGroup. This method does not modify the input address.
   */
  static EquivalentAddressGroup setPathFilter(EquivalentAddressGroup address, List<String> names) {
    checkNotNull(address, "address");
    checkNotNull(names, "names");
    Attributes.Builder attrBuilder = address.getAttributes().toBuilder()
        .set(PATH_CHAIN_KEY, createPathChain(names));
    return new EquivalentAddressGroup(address.getAddresses(), attrBuilder.build());
  }

  /**
   * Creates a PathChain that can be set in an EquivalentAddressGroup's Attributes as a value of
   * PATH_CHAIN_KEY.
   */
  @Nullable static PathChain createPathChain(List<String> names) {
    checkNotNull(names, "names");
    PathChain current = null;
    ListIterator<String> iter = names.listIterator(names.size());
    while (iter.hasPrevious()) {
      current = new PathChain(iter.previous(), current);
    }
    return current;
  }

  /**
   * Returns the next level hierarchical addresses derived from the given hierarchical addresses
   * with the given filter name (any non-hierarchical addresses in the input will be ignored).
   * This method does not modify the input addresses.
   */
  static List<EquivalentAddressGroup> filter(List<EquivalentAddressGroup> addresses, String name) {
    checkNotNull(addresses, "addresses");
    checkNotNull(name, "name");
    List<EquivalentAddressGroup> filteredAddresses = new ArrayList<>();
    for (EquivalentAddressGroup address : addresses) {
      PathChain pathChain = address.getAttributes().get(PATH_CHAIN_KEY);
      if (pathChain != null && pathChain.name.equals(name)) {
        Attributes filteredAddressAttrs =
            address.getAttributes().toBuilder().set(PATH_CHAIN_KEY, pathChain.next).build();
        filteredAddresses.add(
            new EquivalentAddressGroup(address.getAddresses(), filteredAddressAttrs));
      }
    }
    return Collections.unmodifiableList(filteredAddresses);
  }

  static final class PathChain {
    final String name;
    @Nullable final PathChain next;