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From eribeiro <...@git.apache.org>
Subject [GitHub] zookeeper pull request #136: [ZOOKEEPER-1416] Persistent Recursive Watch
Date Tue, 27 Dec 2016 18:55:31 GMT
Github user eribeiro commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/136#discussion_r93960053
  
    --- Diff: src/java/main/org/apache/zookeeper/server/PathIterator.java ---
    @@ -0,0 +1,89 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.zookeeper.server;
    +
    +import java.util.Iterator;
    +
    +/**
    + * Iterates over a ZooKeeper path. Each iteration goes up one parent path. Thus, the
    + * effect of the iterator is to iterate over the initial path and then all of its parents.
    + */
    +public class PathIterator implements Iterator<String> {
    +    private String path;
    +    private int level = -1;
    +
    +    /**
    +     * @param path initial path
    +     */
    +    public PathIterator(String path) {
    +        // NOTE: asserts that the path has already been validated
    +        this.path = path;
    +    }
    +
    +    /**
    +     * Return an Iterable view so that this Iterator can be used in for each
    +     * statements. IMPORTANT: the returned Iterable is single use only
    +     * @return Iterable
    +     */
    +    public Iterable<String> asIterable() {
    +        return new Iterable<String>() {
    +            @Override
    +            public Iterator<String> iterator() {
    +                return PathIterator.this;
    +            }
    +        };
    +    }
    +
    +    @Override
    +    public boolean hasNext() {
    +        return !path.isEmpty();
    +    }
    +
    +    /**
    +     * Returns true if this iterator is currently at a parent path as opposed
    +     * to the initial path given to the constructor
    +     *
    +     * @return true/false
    +     */
    +    public boolean atParentPath() {
    +        return level > 0;
    +    }
    +
    +    @Override
    +    public String next() {
    +        String localPath = path;
    +        if (hasNext()) {
    +            ++level;
    +            if (path.equals("/")) {
    +                path = "";
    +            } else {
    +                path = path.substring(0, path.lastIndexOf('/'));
    +                if (path.length() == 0) {
    +                    path = "/";
    +                }
    +            }
    +        }
    --- End diff --
    
    @Randgalt I had written about this previously, but I think it got lost in my comment flood
yesterday, excuse me:
    
    By the ``Iterator#next()`` contract, if we call next() and there's no next element it
should throw a ``NoSuchElementException``, so an ``else`` clause throwing this exception would
be nice. ;)


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