FSBlobIdIterator.java

/* $HeadURL$
 * $Id$
 *
 * Copyright (c) 2009-2010 DuraSpace
 * http://duraspace.org
 *
 * In collaboration with Topaz Inc.
 * http://www.topazproject.org
 *
 * Licensed 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.akubraproject.fs;

import com.google.common.collect.AbstractIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.net.URI;
import java.net.URISyntaxException;

/**
 * Iterates over all files in baseDir (respecting filterPrefix if provided).
 *
 * @author Chris Wilper
 */
class FSBlobIdIterator extends AbstractIterator<URI> {
  private final Logger log = LoggerFactory.getLogger(FSBlobIdIterator.class);
  private final File baseDir;
  private final String filterPrefix;
  private DirectoryNode currentDir;

  FSBlobIdIterator(File baseDir, String filterPrefix) {
    this.baseDir = baseDir;
    this.filterPrefix = filterPrefix;
    currentDir = new DirectoryNode(null, "");
  }

  @Override
  protected URI computeNext() {
    while (currentDir != null) {
      DirectoryNode child = currentDir.nextChild();
      if (child == null) {
        // no more children; move up
        currentDir = currentDir.parent;
      } else if (child.isDirectory()) {
        // child is dir; move down
        currentDir = child;
      } else {
        // child is file
        try {
          URI uri = new URI(FSBlob.scheme + ":" + child.path);
          if (filterPrefix == null || uri.toString().startsWith(filterPrefix)) {
            return uri;
          }
        } catch (URISyntaxException e) {
          log.warn("Skipping non-URI-safe file: {}", child.path);
        }
      }
    }

    return endOfData(); // exhausted
  }

  private class DirectoryNode {

    final DirectoryNode parent;

    final String path;

    private String[] childPaths;

    private int childNum;

    DirectoryNode(DirectoryNode parent,  // null if root
                  String path) {         // "" if root, "name/" if subdir, "name" if file
      this.parent = parent;
      this.path = path;
      if (isDirectory()) {
        setChildPaths();
      }
    }

    private void setChildPaths() {
      File dir;
      if (path.length() == 0) {
        dir = baseDir;
      } else {
        dir = new File(baseDir, path);
      }
      File[] childFiles = dir.listFiles();
      childPaths = new String[childFiles.length];
      for (int i = 0; i < childFiles.length; i++) {
        StringBuilder childPath = new StringBuilder(path);
        childPath.append(childFiles[i].getName());
        if (childFiles[i].isDirectory()) {
          childPath.append("/");
        }
        childPaths[i] = childPath.toString();
      }
    }

    boolean isDirectory() {
      return path.length() == 0 || path.endsWith("/");
    }

    DirectoryNode nextChild() {
      if (isDirectory()) {
        if (childNum == childPaths.length) {
          return null;  // no more children
        } else {
          return new DirectoryNode(this, childPaths[childNum++]);
        }
      } else {
        return null;   // not a directory
      }
    }
  }
}