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//
// XmlCachingResolver.cs
//
// Author:
// Ben Maurer (bmaurer@users.sourceforge.net)
//
// (C) 2003 Ben Maurer
//
using System;
using System.Xml;
using System.Net;
using System.IO;
namespace Mono.Xml {
public class XmlCachingResolver : XmlUrlResolver {
static string tmpFolder;
static XmlCachingResolver ()
{
tmpFolder = Path.Combine (Path.GetTempPath (), "XmlCachingResolver_Cache");
Directory.CreateDirectory (tmpFolder);
}
#region XmlResolver impl
ICredentials credentials;
public override ICredentials Credentials
{
set { credentials = value; }
}
public override object GetEntity (Uri absoluteUri, string role, Type ofObjectToReturn)
{
if (ofObjectToReturn == null || ofObjectToReturn == typeof (Stream))
return GetStream (absoluteUri);
else
throw new XmlException ("Unsupported class type: " + ofObjectToReturn);
}
Stream GetStream (Uri uri)
{
// We can handle file:// without all the excess System.Net stuff
if (uri.Scheme == "file")
return File.OpenRead (uri.LocalPath);
else {
WebRequest req = WebRequest.Create (uri);
if (credentials != null)
req.Credentials = credentials;
if (req is HttpWebRequest) {
string url = uri.ToString ();
if (File.Exists (GetCachedPath (url))) {
// The file is in the cache, lets make sure it is up to date
HttpWebRequest hreq = req as HttpWebRequest;
// MS has a bug in their .net that makes 3xx errors (such as NotModified, 304)
// throw when this is *TRUE* even though their docs say it will throw when *FALSE*
hreq.AllowAutoRedirect = false;
hreq.IfModifiedSince = File.GetLastWriteTime (GetCachedPath (url));
HttpWebResponse hresp = hreq.GetResponse () as HttpWebResponse;
if (hresp.StatusCode != HttpStatusCode.NotModified)
using (Stream s = hresp.GetResponseStream ())
AddToCache (url, s);
return GetFromCache (url);
} else {
// The file has not been cached yet, so lets just get it
// and add it there.
using (Stream s = req.GetResponse ().GetResponseStream ())
AddToCache (url, s);
return GetFromCache (url);
}
} else // Ok, its not a http request, we dont know how to cache this
return req.GetResponse ().GetResponseStream ();
}
}
#endregion
#region Caching
static void AddToCache (string url, Stream data)
{
const int cbBuff = 8192;
int cb = 0;
byte [] buff = new byte [cbBuff];
using (FileStream fs = File.Create (GetCachedPath (url))) {
do {
cb = data.Read (buff, 0, cbBuff);
fs.Write (buff, 0, cb);
} while (cb > 0) ;
}
}
static string GetCachedPath (string url)
{
// EncodeLocalName will take out all things that would
// be bad to have in the file system
return Path.Combine (tmpFolder, XmlConvert.EncodeLocalName (url));
}
static Stream GetFromCache (string url)
{
return File.OpenRead (GetCachedPath (url));
}
#endregion
// utility method to make reading from this easier.
public XmlReader GetXmlReader (string url)
{
Uri uri = ResolveUri (null, url);
Stream stream = (Stream)GetEntity (uri, null, typeof (Stream));
XmlTextReader ret = new XmlTextReader (url, stream);
ret.XmlResolver = this;
return ret;
}
}
}
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