/**
   * @param sourceFile File to read from
   * @return List of String objects with the shas
   */
  public static FileRequestFileContent readRequestFile(final File sourceFile) {
    if (!sourceFile.isFile() || !(sourceFile.length() > 0)) {
      return null;
    }
    Document d = null;
    try {
      d = XMLTools.parseXmlFile(sourceFile.getPath());
    } catch (final Throwable t) {
      logger.log(Level.SEVERE, "Exception in readRequestFile, during XML parsing", t);
      return null;
    }

    if (d == null) {
      logger.log(Level.SEVERE, "Could'nt parse the request file");
      return null;
    }

    final Element rootNode = d.getDocumentElement();

    if (rootNode.getTagName().equals(TAG_FrostFileRequestFile) == false) {
      logger.severe(
          "Error: xml request file does not contain the root tag '"
              + TAG_FrostFileRequestFile
              + "'");
      return null;
    }

    final String timeStampStr = XMLTools.getChildElementsTextValue(rootNode, TAG_timestamp);
    if (timeStampStr == null) {
      logger.severe("Error: xml file does not contain the tag '" + TAG_timestamp + "'");
      return null;
    }
    final long timestamp = Long.parseLong(timeStampStr);

    final List<Element> nodelist = XMLTools.getChildElementsByTagName(rootNode, TAG_shaList);
    if (nodelist.size() != 1) {
      logger.severe("Error: xml request files must contain only one element '" + TAG_shaList + "'");
      return null;
    }

    final Element rootShaNode = nodelist.get(0);

    final List<String> shaList = new LinkedList<String>();
    final List<Element> xmlKeys = XMLTools.getChildElementsByTagName(rootShaNode, TAG_sha);
    for (final Element el : xmlKeys) {

      final Text txtname = (Text) el.getFirstChild();
      if (txtname == null) {
        continue;
      }

      final String sha = txtname.getData();
      shaList.add(sha);
    }

    final FileRequestFileContent content = new FileRequestFileContent(timestamp, shaList);
    return content;
  }
 /**
  * Enqueue a direct GET if not already enqueued, or already downloaded to download dir.
  *
  * @return true if item was enqueued
  */
 public boolean maybeEnqueueDirectGet(
     final FrostDownloadItem dlItem, final long expectedFileSize) {
   if (!isDirectTransferInProgress(dlItem)) {
     final File targetFile = new File(dlItem.getDownloadFilename());
     if (!targetFile.isFile() || targetFile.length() != expectedFileSize) {
       directTransferQueue.appendItemToQueue(dlItem);
       return true;
     }
   }
   return false;
 }