/// <summary>
/// Saves a particular RSS feed.
/// </summary>
/// <remarks>This method should be thread-safe</remarks>
/// <param name="feed">The feed to save. This is an identifier
/// and not used to actually fetch the feed from the WWW.</param>
/// <returns>An identifier for the saved feed. </returns>
public override string SaveFeed(IInternalFeedDetails feed)
{
string feedLocation = feed.FeedLocation;
lock (this)
{
if (string.IsNullOrEmpty(feed.FeedLocation))
{
feed.FeedLocation = feedLocation = GetCacheUrlName(feed.Id, new Uri(feed.Link));
}
}
//get location of binary file containing RSS item contents
string feedContentLocation = feedLocation.Substring(0, feedLocation.Length - 4) + ".bin";
//write main RSS feed
var tempFile = Path.GetTempFileName();
using (FileStream stream = FileHelper.OpenForWrite(tempFile))
{
XmlTextWriter writer = new XmlTextWriter(new StreamWriter(stream));
feed.WriteTo(writer, true);
writer.Flush();
}
FileHelper.MoveFile(tempFile, Path.Combine(CacheLocation, feedLocation), MoveFileFlag.ReplaceExisting);
//write binary file containing RSS item contents
tempFile = Path.GetTempFileName();
using (FileStream stream = FileHelper.OpenForWrite(tempFile))
{
var writer = new BinaryWriter(stream);
FileStream fs = null;
BinaryReader reader = null;
try
{
if (File.Exists(Path.Combine(CacheLocation, feedContentLocation)))
{
fs = new FileStream(Path.Combine(CacheLocation, feedContentLocation), FileMode.OpenOrCreate);
reader = new BinaryReader(fs);
}
feed.WriteItemContents(reader, writer);
writer.Write(FileHelper.EndOfBinaryFileMarker);
writer.Flush();
}
finally
{
if (fs != null)
{
fs.Close();
}
}
} //using(...)
FileHelper.MoveFile(tempFile, Path.Combine(CacheLocation, feedContentLocation), MoveFileFlag.ReplaceExisting);
return(feedLocation);
}
/// <summary>
/// Returns an RSS feed.
/// </summary>
/// <param name="feed">The feed whose FeedInfo is required.</param>
/// <returns>The requested feed or null if it doesn't exist</returns>
public override IInternalFeedDetails GetFeed(INewsFeed feed)
{
if (null == feed || null == feed.cacheurl)
{
return(null);
}
IInternalFeedDetails fi = null;
string cachelocation = Path.Combine(CacheLocation, feed.cacheurl);
if (File.Exists(cachelocation))
{
using (Stream feedStream = FileHelper.OpenForRead(cachelocation)) {
fi = RssParser.GetItemsForFeed(feed, feedStream, true);
}
this.LoadItemContent(fi);
}
return(fi);
}
/// <summary> /// Saves a particular RSS feed. /// </summary> /// <remarks>This method should be thread-safe</remarks> /// <param name="feed">The feed to save. This is an identifier /// and not used to actually fetch the feed from the WWW.</param> /// <returns>The feed ID</returns> public abstract string SaveFeed(IInternalFeedDetails feed);
/// <summary>
/// Loads the content of the unread NewsItems from the binary file
/// where item contents are contained. This is a memory-saving performance
/// optimization so we only have the content of items that are unread on load.
/// </summary>
/// <param name="fi"></param>
private void LoadItemContent(IInternalFeedDetails fi)
{
if (fi == null)
{
return;
}
Hashtable unreadItems = new Hashtable();
FileStream fs = null;
BinaryReader reader = null;
//get list of unread items
foreach (NewsItem item in fi.ItemsList)
{
if (!item.BeenRead)
{
try
{
unreadItems.Add(item.Id, item);
}
catch (ArgumentException)
{
/* we don't test using ContainsKey() before Add() for performance reasons */
}
}
}
try
{
string feedContentLocation = fi.FeedLocation.Substring(0, fi.FeedLocation.Length - 4) + ".bin";
string fileName = Path.Combine(CacheLocation, feedContentLocation);
if (File.Exists(fileName))
{
fs = FileHelper.OpenForRead(fileName);
reader = new BinaryReader(fs);
string id = reader.ReadString();
while (!string.IsNullOrEmpty(id) && !id.Equals(FileHelper.EndOfBinaryFileMarker))
{
int count = reader.ReadInt32();
byte[] content = reader.ReadBytes(count);
if (unreadItems.Contains(id))
{
NewsItem ni = (NewsItem)unreadItems[id];
ni.SetContent(content, ContentType.Html);
}
id = reader.ReadString();
} //while(!id.Equals(...))
}
}
finally
{
if (fs != null)
{
fs.Close();
}
}
}