Created a generic RESTClient component, which simplifies querying for resources from REST based web-services.

Currently it supports a barebones scheme for specifying the path of the resource and querying asynchroneously. POST method is still wacky and a good solid scheme for handling timeout still remain.
author: Tleiades Hax 2007-10-25 09:26:47 +0000
committer: Tleiades Hax 2007-10-25 09:26:47 +0000
commit: 60e45418654975d27633a683b57c7013b98a23e3 (patch)
tree: 19e41032d405d29f203139f4c2ad62ac429fd1f1 /OpenSim/Framework/Communications/RestClient
parent: updated libode.so (no exception on assert) (diff)
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2 files changed, 491 insertions, 0 deletions
diff --git a/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs
new file mode 100644
index 0000000..4be459d
--- /dev/null
+++ b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs
@@ -0,0 +1,163 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+namespace OpenSim.Framework.RestClient
+{
+    internal class SimpleAsyncResult : IAsyncResult
+    {
+        private readonly AsyncCallback m_callback;
+        /// <summary>
+        /// Is process completed?
+        /// </summary>
+        /// <remarks>Should really be boolean, but VolatileRead has no boolean method</remarks>
+        private byte m_completed;
+        /// <summary>
+        /// Did process complete synchroneously?
+        /// </summary>
+        /// <remarks>I have a hard time imagining a scenario where this is the case, again, same issue about
+        /// booleans and VolatileRead as m_completed
+        /// </remarks>
+        private byte m_completedSynchronously;
+        private readonly object m_asyncState;
+        private ManualResetEvent m_waitHandle;
+        private Exception m_exception;
+        internal SimpleAsyncResult(AsyncCallback cb, object state)
+        {
+            m_callback = cb;
+            m_asyncState = state;
+            m_completed = 0;
+            m_completedSynchronously = 1;
+        }
+        #region IAsyncResult Members
+        public object AsyncState
+        {
+            get { return m_asyncState; }
+        }
+        public WaitHandle AsyncWaitHandle
+        {
+            get
+            {
+                if (m_waitHandle == null)
+                {
+                    bool done = IsCompleted;
+                    ManualResetEvent mre = new ManualResetEvent(done);
+                    if (Interlocked.CompareExchange(ref m_waitHandle, mre, null) != null)
+                    {
+                        mre.Close();
+                    }
+                    else
+                    {
+                        if (!done && IsCompleted)
+                        {
+                            m_waitHandle.Set();
+                        }
+                    }
+                }
+                return m_waitHandle;
+            }
+        }
+        public bool CompletedSynchronously
+        {
+            get { return Thread.VolatileRead(ref m_completedSynchronously) == 1; }
+        }
+        public bool IsCompleted
+        {
+            get { return Thread.VolatileRead(ref m_completed) == 1; }
+        }
+        #endregion
+        #region class Methods
+        internal void SetAsCompleted(bool completedSynchronously)
+        {
+            m_completed = 1;
+            if(completedSynchronously)
+                m_completedSynchronously = 1;
+            else
+                m_completedSynchronously = 0;
+            
+            SignalCompletion();
+        }
+        internal void HandleException(Exception e, bool completedSynchronously)
+        {
+            m_completed = 1;
+            if (completedSynchronously)
+                m_completedSynchronously = 1;
+            else
+                m_completedSynchronously = 0;
+            m_exception = e;
+            SignalCompletion();
+        }
+        private void SignalCompletion()
+        {
+            if(m_waitHandle != null) m_waitHandle.Set();
+            if(m_callback != null) m_callback(this);
+        }
+        public void EndInvoke()
+        {
+            // This method assumes that only 1 thread calls EndInvoke 
+            if (!IsCompleted)
+            {
+                // If the operation isn't done, wait for it
+                AsyncWaitHandle.WaitOne();
+                AsyncWaitHandle.Close();
+                m_waitHandle = null;  // Allow early GC
+            }
+            // Operation is done: if an exception occured, throw it
+            if (m_exception != null) throw m_exception;
+        }       
+        #endregion 
+    }
+    internal class AsyncResult<T> : SimpleAsyncResult
+    {
+        private T m_result = default(T);
+        public AsyncResult(AsyncCallback asyncCallback, Object state) :
+            base(asyncCallback, state) { }
+        public void SetAsCompleted(T result,  bool completedSynchronously)
+        {
+            // Save the asynchronous operation's result
+            m_result = result;
+            // Tell the base class that the operation completed 
+            // sucessfully (no exception)
+            base.SetAsCompleted(completedSynchronously);
+        }
+        new public T EndInvoke()
+        {
+            base.EndInvoke(); 
+            return m_result;  
+        }
+    }
+}
diff --git a/OpenSim/Framework/Communications/RestClient/RestClient.cs b/OpenSim/Framework/Communications/RestClient/RestClient.cs
new file mode 100644
index 0000000..ccf8376
--- /dev/null
+++ b/OpenSim/Framework/Communications/RestClient/RestClient.cs
@@ -0,0 +1,328 @@
+using System;
+using System.IO;
+using System.Net;
+using System.Web;
+using System.Text;
+using System.Collections.Generic;
+using System.Threading;
+namespace OpenSim.Framework.RestClient
+{
+    /// <summary>
+    /// Implementation of a generic REST client
+    /// </summary>
+    /// <remarks>
+    /// This class is a generic implementation of a REST (Representational State Transfer) web service. This
+    /// class is designed to execute both synchroneously and asynchroneously.
+    /// 
+    /// Internally the implementation works as a two stage asynchroneous web-client.
+    /// When the request is initiated, RestClient will query asynchroneously for for a web-response,
+    /// sleeping until the initial response is returned by the server. Once the initial response is retrieved
+    /// the second stage of asynchroneous requests will be triggered, in an attempt to read of the response
+    /// object into a memorystream as a sequence of asynchroneous reads.
+    /// 
+    /// The asynchronisity of RestClient is designed to move as much processing into the back-ground, allowing 
+    /// other threads to execute, while it waits for a response from the web-service. RestClient it self, can be
+    /// invoked by the caller in either synchroneous mode or asynchroneous mode.
+    /// </remarks>
+    public class RestClient 
+    {
+        /// <summary>
+        /// The base Uri of the web-service e.g. http://www.google.com 
+        /// </summary>
+        private string _url;
+        /// <summary>
+        /// Path elements of the query
+        /// </summary>
+        private List<string> _pathElements = new List<string>();
+        /// <summary>
+        /// Parameter elements of the query, e.g. min=34
+        /// </summary>
+        private Dictionary<string, string> _parameterElements = new Dictionary<string, string>();
+        /// <summary>
+        /// Request method. E.g. GET, POST, PUT or DELETE
+        /// </summary>
+        private string _method;
+        /// <summary>
+        /// Temporary buffer used to store bytes temporarily as they come in from the server
+        /// </summary>
+        private byte[] _readbuf;
+        /// <summary>
+        /// MemoryStream representing the resultiong resource
+        /// </summary>
+        MemoryStream _resource;
+        /// <summary>
+        /// WebRequest object, held as a member variable
+        /// </summary>
+        private HttpWebRequest _request;
+        /// <summary>
+        /// WebResponse object, held as a member variable, so we can close it
+        /// </summary>
+        private HttpWebResponse _response;
+        /// <summary>
+        /// This flag will help block the main synchroneous method, in case we run in synchroneous mode
+        /// </summary>
+        public static ManualResetEvent _allDone = new ManualResetEvent(false);
+        /// <summary>
+        /// Default time out period
+        /// </summary>
+        const int DefaultTimeout = 10 * 1000; // 10 seconds timeout
+        /// <summary>
+        /// Default Buffer size of a block requested from the web-server
+        /// </summary>
+        const int BufferSize = 4096; // Read blocks of 4 KB.
+        /// <summary>
+        /// if an exception occours during async processing, we need to save it, so it can be 
+        /// rethrown on the primary thread;
+        /// </summary>
+        private Exception _asyncException;
+        /// <summary>
+        /// Instantiate a new RestClient
+        /// </summary>
+        /// <param name="url">Web-service to query, e.g. http://osgrid.org:8003</param>
+        public RestClient(string url)
+        {
+            _url = url;
+            _readbuf = new byte[BufferSize];
+            _resource = new MemoryStream();
+            _request = null;
+            _response = null;
+        }
+        /// <summary>
+        /// Add a path element to the query, e.g. assets
+        /// </summary>
+        /// <param name="element">path entry</param>
+        public void AddResourcePath(string element)
+        {
+            if(isSlashed(element))
+                _pathElements.Add(element.Substring(0, element.Length-1));
+            else
+                _pathElements.Add(element);
+        }
+        /// <summary>
+        /// Add a query parameter to the Url
+        /// </summary>
+        /// <param name="name">Name of the parameter, e.g. min</param>
+        /// <param name="value">Value of the parameter, e.g. 42</param>
+        public void AddQueryParameter(string name, string value)
+        {
+            _parameterElements.Add(HttpUtility.UrlEncode(name), HttpUtility.UrlEncode(value));
+        }
+        /// <summary>
+        /// Web-Request method, e.g. GET, PUT, POST, DELETE
+        /// </summary>
+        public string RequestMethod
+        {
+            get { return _method; }
+            set { _method = value; }
+        }
+        /// <summary>
+        /// True if string contains a trailing slash '/'
+        /// </summary>
+        /// <param name="s">string to be examined</param>
+        /// <returns>true if slash is present</returns>
+        private bool isSlashed(string s)
+        {
+            return s.Substring(s.Length - 1, 1) == "/";
+        }
+        /// <summary>
+        /// return a slash or blank. A slash will be returned if the string does not contain one
+        /// </summary>
+        /// <param name="s">stromg to be examined</param>
+        /// <returns>slash '/' if not already present</returns>
+        private string slash(string s)
+        {
+            return isSlashed(s) ? "" : "/";
+        }
+        /// <summary>
+        /// Build a Uri based on the intial Url, path elements and parameters
+        /// </summary>
+        /// <returns>fully constructed Uri</returns>
+        Uri buildUri()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append(_url);
+            foreach (string e in _pathElements)
+            {
+                sb.Append("/");
+                sb.Append(e);
+            }
+            bool firstElement = true;
+            foreach (KeyValuePair<string, string> kv in _parameterElements)
+            {
+                if (firstElement)
+                {
+                    sb.Append("?");
+                    firstElement = false;
+                } else
+                    sb.Append("&");
+                sb.Append(kv.Key);
+                if (kv.Value != null && kv.Value.Length != 0)
+                {
+                    sb.Append("=");
+                    sb.Append(kv.Value);
+                }
+            }
+            return new Uri(sb.ToString());
+        }
+        /// <summary>
+        /// Async method, invoked when a block of data has been received from the service
+        /// </summary>
+        /// <param name="ar"></param>
+        private void StreamIsReadyDelegate(IAsyncResult ar)
+        {
+            try
+            {
+                Stream s = (Stream)ar.AsyncState;
+                int read = s.EndRead(ar);
+                // Read the HTML page and then print it to the console.
+                if (read > 0)
+                {
+                    _resource.Write(_readbuf, 0, read);
+                    IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
+                    // TODO! Implement timeout, without killing the server
+                    //ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
+                    return;
+                }
+                else
+                {
+                    s.Close();
+                    _allDone.Set();
+                }
+            }
+            catch (Exception e)
+            {
+                _allDone.Set();
+                _asyncException = e;
+            }
+        }
+        /// <summary>
+        /// Async method, invoked when the intial response if received from the server
+        /// </summary>
+        /// <param name="ar"></param>
+        private void ResponseIsReadyDelegate(IAsyncResult ar)
+        {
+            try
+            {
+                // grab response
+                WebRequest wr = (WebRequest)ar.AsyncState;
+                _response = (HttpWebResponse)wr.EndGetResponse(ar);
+                // get response stream, and setup async reading
+                Stream s = _response.GetResponseStream();
+                IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
+                // TODO! Implement timeout, without killing the server
+                // wait until completed, or we timed out
+                // ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
+            }
+            catch (Exception e)
+            {
+                _allDone.Set();
+                _asyncException = e;
+            }
+        }
+        // Abort the request if the timer fires.
+        private static void TimeoutCallback(object state, bool timedOut)
+        {
+            if (timedOut)
+            {
+                HttpWebRequest request = state as HttpWebRequest;
+                if (request != null)
+                {
+                    request.Abort();
+                }
+            }
+        }
+        /// <summary>
+        /// Perform synchroneous request
+        /// </summary>
+        public Stream Request()
+        {
+            _request = (HttpWebRequest)WebRequest.Create(buildUri());
+            _request.KeepAlive = false;
+            _request.ContentType = "text/html";
+            _request.Timeout = 200;
+            _asyncException = null;
+            IAsyncResult responseAsyncResult = _request.BeginGetResponse(new AsyncCallback(ResponseIsReadyDelegate), _request);
+            // TODO! Implement timeout, without killing the server
+            // this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
+            //ThreadPool.RegisterWaitForSingleObject(responseAsyncResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
+            _allDone.WaitOne();
+            if(_response != null)
+                _response.Close();
+            if (_asyncException != null)
+                throw _asyncException;
+            return _resource;
+        }
+        #region Async Invocation
+        public IAsyncResult BeginRequest(AsyncCallback callback, object state)
+        {
+            /// <summary>
+            /// In case, we are invoked asynchroneously this object will keep track of the state
+            /// </summary>
+            AsyncResult<Stream> ar = new AsyncResult<Stream>(callback, state);
+            ThreadPool.QueueUserWorkItem(RequestHelper, ar);
+            return ar;
+        }
+        public Stream EndRequest(IAsyncResult asyncResult)
+        {
+            AsyncResult<Stream> ar = (AsyncResult<Stream>)asyncResult;
+            // Wait for operation to complete, then return result or 
+            // throw exception
+            return ar.EndInvoke();
+        }
+        private void RequestHelper(Object asyncResult)
+        {
+            // We know that it's really an AsyncResult<DateTime> object
+            AsyncResult<Stream> ar = (AsyncResult<Stream>)asyncResult;
+            try
+            {
+                // Perform the operation; if sucessful set the result
+                Stream s = Request();
+                ar.SetAsCompleted(s, false);
+            }
+            catch (Exception e)
+            {
+                // If operation fails, set the exception
+                ar.HandleException(e, false);
+            }
+        }
+        #endregion Async Invocation
+    }
+}
author	Tleiades Hax	2007-10-25 09:26:47 +0000
committer	Tleiades Hax	2007-10-25 09:26:47 +0000
commit	60e45418654975d27633a683b57c7013b98a23e3 (patch)
tree	19e41032d405d29f203139f4c2ad62ac429fd1f1 /OpenSim/Framework/Communications/RestClient
parent	updated libode.so (no exception on assert) (diff)
download	opensim-SC-60e45418654975d27633a683b57c7013b98a23e3.zip opensim-SC-60e45418654975d27633a683b57c7013b98a23e3.tar.gz opensim-SC-60e45418654975d27633a683b57c7013b98a23e3.tar.bz2 opensim-SC-60e45418654975d27633a683b57c7013b98a23e3.tar.xz

diff --git a/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs new file mode 100644 index 0000000..4be459d --- /dev/null +++ b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs
@@ -0,0 +1,163 @@
	1	using System;
	2	using System.Collections.Generic;
	3	using System.Text;
	4	using System.Threading;
	5
	6	namespace OpenSim.Framework.RestClient
	7	{
	8	internal class SimpleAsyncResult : IAsyncResult
	9	{
	10
	11	private readonly AsyncCallback m_callback;
	12
	13	/// <summary>
	14	/// Is process completed?
	15	/// </summary>
	16	/// <remarks>Should really be boolean, but VolatileRead has no boolean method</remarks>
	17	private byte m_completed;
	18
	19	/// <summary>
	20	/// Did process complete synchroneously?
	21	/// </summary>
	22	/// <remarks>I have a hard time imagining a scenario where this is the case, again, same issue about
	23	/// booleans and VolatileRead as m_completed
	24	/// </remarks>
	25	private byte m_completedSynchronously;
	26
	27	private readonly object m_asyncState;
	28	private ManualResetEvent m_waitHandle;
	29	private Exception m_exception;
	30
	31	internal SimpleAsyncResult(AsyncCallback cb, object state)
	32	{
	33	m_callback = cb;
	34	m_asyncState = state;
	35	m_completed = 0;
	36	m_completedSynchronously = 1;
	37	}
	38
	39
	40	#region IAsyncResult Members
	41
	42	public object AsyncState
	43	{
	44	get { return m_asyncState; }
	45	}
	46
	47
	48
	49	public WaitHandle AsyncWaitHandle
	50	{
	51	get
	52	{
	53	if (m_waitHandle == null)
	54	{
	55	bool done = IsCompleted;
	56	ManualResetEvent mre = new ManualResetEvent(done);
	57	if (Interlocked.CompareExchange(ref m_waitHandle, mre, null) != null)
	58	{
	59	mre.Close();
	60	}
	61	else
	62	{
	63	if (!done && IsCompleted)
	64	{
	65	m_waitHandle.Set();
	66	}
	67	}
	68	}
	69	return m_waitHandle;
	70	}
	71	}
	72
	73
	74	public bool CompletedSynchronously
	75	{
	76	get { return Thread.VolatileRead(ref m_completedSynchronously) == 1; }
	77	}
	78
	79
	80	public bool IsCompleted
	81	{
	82	get { return Thread.VolatileRead(ref m_completed) == 1; }
	83	}
	84
	85
	86	#endregion
	87
	88
	89	#region class Methods
	90	internal void SetAsCompleted(bool completedSynchronously)
	91	{
	92	m_completed = 1;
	93	if(completedSynchronously)
	94	m_completedSynchronously = 1;
	95	else
	96	m_completedSynchronously = 0;
	97
	98	SignalCompletion();
	99	}
	100
	101	internal void HandleException(Exception e, bool completedSynchronously)
	102	{
	103	m_completed = 1;
	104	if (completedSynchronously)
	105	m_completedSynchronously = 1;
	106	else
	107	m_completedSynchronously = 0;
	108	m_exception = e;
	109
	110	SignalCompletion();
	111	}
	112
	113	private void SignalCompletion()
	114	{
	115	if(m_waitHandle != null) m_waitHandle.Set();
	116
	117	if(m_callback != null) m_callback(this);
	118	}
	119
	120	public void EndInvoke()
	121	{
	122	// This method assumes that only 1 thread calls EndInvoke
	123	if (!IsCompleted)
	124	{
	125	// If the operation isn't done, wait for it
	126	AsyncWaitHandle.WaitOne();
	127	AsyncWaitHandle.Close();
	128	m_waitHandle = null; // Allow early GC
	129	}
	130
	131	// Operation is done: if an exception occured, throw it
	132	if (m_exception != null) throw m_exception;
	133	}
	134
	135	#endregion
	136	}
	137
	138	internal class AsyncResult<T> : SimpleAsyncResult
	139	{
	140	private T m_result = default(T);
	141
	142	public AsyncResult(AsyncCallback asyncCallback, Object state) :
	143	base(asyncCallback, state) { }
	144
	145
	146	public void SetAsCompleted(T result, bool completedSynchronously)
	147	{
	148	// Save the asynchronous operation's result
	149	m_result = result;
	150
	151	// Tell the base class that the operation completed
	152	// sucessfully (no exception)
	153	base.SetAsCompleted(completedSynchronously);
	154	}
	155
	156	new public T EndInvoke()
	157	{
	158	base.EndInvoke();
	159	return m_result;
	160	}
	161
	162	}
	163	}


diff --git a/OpenSim/Framework/Communications/RestClient/RestClient.cs b/OpenSim/Framework/Communications/RestClient/RestClient.cs new file mode 100644 index 0000000..ccf8376 --- /dev/null +++ b/OpenSim/Framework/Communications/RestClient/RestClient.cs
@@ -0,0 +1,328 @@
	1	using System;
	2	using System.IO;
	3	using System.Net;
	4	using System.Web;
	5	using System.Text;
	6	using System.Collections.Generic;
	7	using System.Threading;
	8
	9	namespace OpenSim.Framework.RestClient
	10	{
	11	/// <summary>
	12	/// Implementation of a generic REST client
	13	/// </summary>
	14	/// <remarks>
	15	/// This class is a generic implementation of a REST (Representational State Transfer) web service. This
	16	/// class is designed to execute both synchroneously and asynchroneously.
	17	///
	18	/// Internally the implementation works as a two stage asynchroneous web-client.
	19	/// When the request is initiated, RestClient will query asynchroneously for for a web-response,
	20	/// sleeping until the initial response is returned by the server. Once the initial response is retrieved
	21	/// the second stage of asynchroneous requests will be triggered, in an attempt to read of the response
	22	/// object into a memorystream as a sequence of asynchroneous reads.
	23	///
	24	/// The asynchronisity of RestClient is designed to move as much processing into the back-ground, allowing
	25	/// other threads to execute, while it waits for a response from the web-service. RestClient it self, can be
	26	/// invoked by the caller in either synchroneous mode or asynchroneous mode.
	27	/// </remarks>
	28	public class RestClient
	29	{
	30	/// <summary>
	31	/// The base Uri of the web-service e.g. http://www.google.com
	32	/// </summary>
	33	private string _url;
	34
	35	/// <summary>
	36	/// Path elements of the query
	37	/// </summary>
	38	private List<string> _pathElements = new List<string>();
	39
	40	/// <summary>
	41	/// Parameter elements of the query, e.g. min=34
	42	/// </summary>
	43	private Dictionary<string, string> _parameterElements = new Dictionary<string, string>();
	44
	45	/// <summary>
	46	/// Request method. E.g. GET, POST, PUT or DELETE
	47	/// </summary>
	48	private string _method;
	49
	50	/// <summary>
	51	/// Temporary buffer used to store bytes temporarily as they come in from the server
	52	/// </summary>
	53	private byte[] _readbuf;
	54
	55	/// <summary>
	56	/// MemoryStream representing the resultiong resource
	57	/// </summary>
	58	MemoryStream _resource;
	59
	60	/// <summary>
	61	/// WebRequest object, held as a member variable
	62	/// </summary>
	63	private HttpWebRequest _request;
	64
	65	/// <summary>
	66	/// WebResponse object, held as a member variable, so we can close it
	67	/// </summary>
	68	private HttpWebResponse _response;
	69
	70	/// <summary>
	71	/// This flag will help block the main synchroneous method, in case we run in synchroneous mode
	72	/// </summary>
	73	public static ManualResetEvent _allDone = new ManualResetEvent(false);
	74
	75	/// <summary>
	76	/// Default time out period
	77	/// </summary>
	78	const int DefaultTimeout = 10 * 1000; // 10 seconds timeout
	79
	80	/// <summary>
	81	/// Default Buffer size of a block requested from the web-server
	82	/// </summary>
	83	const int BufferSize = 4096; // Read blocks of 4 KB.
	84
	85
	86	/// <summary>
	87	/// if an exception occours during async processing, we need to save it, so it can be
	88	/// rethrown on the primary thread;
	89	/// </summary>
	90	private Exception _asyncException;
	91
	92	/// <summary>
	93	/// Instantiate a new RestClient
	94	/// </summary>
	95	/// <param name="url">Web-service to query, e.g. http://osgrid.org:8003</param>
	96	public RestClient(string url)
	97	{
	98	_url = url;
	99	_readbuf = new byte[BufferSize];
	100	_resource = new MemoryStream();
	101	_request = null;
	102	_response = null;
	103	}
	104
	105	/// <summary>
	106	/// Add a path element to the query, e.g. assets
	107	/// </summary>
	108	/// <param name="element">path entry</param>
	109	public void AddResourcePath(string element)
	110	{
	111	if(isSlashed(element))
	112	_pathElements.Add(element.Substring(0, element.Length-1));
	113	else
	114	_pathElements.Add(element);
	115	}
	116
	117	/// <summary>
	118	/// Add a query parameter to the Url
	119	/// </summary>
	120	/// <param name="name">Name of the parameter, e.g. min</param>
	121	/// <param name="value">Value of the parameter, e.g. 42</param>
	122	public void AddQueryParameter(string name, string value)
	123	{
	124	_parameterElements.Add(HttpUtility.UrlEncode(name), HttpUtility.UrlEncode(value));
	125	}
	126
	127	/// <summary>
	128	/// Web-Request method, e.g. GET, PUT, POST, DELETE
	129	/// </summary>
	130	public string RequestMethod
	131	{
	132	get { return _method; }
	133	set { _method = value; }
	134	}
	135
	136	/// <summary>
	137	/// True if string contains a trailing slash '/'
	138	/// </summary>
	139	/// <param name="s">string to be examined</param>
	140	/// <returns>true if slash is present</returns>
	141	private bool isSlashed(string s)
	142	{
	143	return s.Substring(s.Length - 1, 1) == "/";
	144	}
	145
	146	/// <summary>
	147	/// return a slash or blank. A slash will be returned if the string does not contain one
	148	/// </summary>
	149	/// <param name="s">stromg to be examined</param>
	150	/// <returns>slash '/' if not already present</returns>
	151	private string slash(string s)
	152	{
	153	return isSlashed(s) ? "" : "/";
	154	}
	155
	156	/// <summary>
	157	/// Build a Uri based on the intial Url, path elements and parameters
	158	/// </summary>
	159	/// <returns>fully constructed Uri</returns>
	160	Uri buildUri()
	161	{
	162	StringBuilder sb = new StringBuilder();
	163	sb.Append(_url);
	164
	165	foreach (string e in _pathElements)
	166	{
	167	sb.Append("/");
	168	sb.Append(e);
	169	}
	170
	171	bool firstElement = true;
	172	foreach (KeyValuePair<string, string> kv in _parameterElements)
	173	{
	174	if (firstElement)
	175	{
	176	sb.Append("?");
	177	firstElement = false;
	178	} else
	179	sb.Append("&");
	180
	181	sb.Append(kv.Key);
	182	if (kv.Value != null && kv.Value.Length != 0)
	183	{
	184	sb.Append("=");
	185	sb.Append(kv.Value);
	186	}
	187	}
	188	return new Uri(sb.ToString());
	189	}
	190
	191	/// <summary>
	192	/// Async method, invoked when a block of data has been received from the service
	193	/// </summary>
	194	/// <param name="ar"></param>
	195	private void StreamIsReadyDelegate(IAsyncResult ar)
	196	{
	197	try
	198	{
	199	Stream s = (Stream)ar.AsyncState;
	200	int read = s.EndRead(ar);
	201
	202	// Read the HTML page and then print it to the console.
	203	if (read > 0)
	204	{
	205	_resource.Write(_readbuf, 0, read);
	206	IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
	207
	208	// TODO! Implement timeout, without killing the server
	209	//ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
	210	return;
	211	}
	212	else
	213	{
	214	s.Close();
	215	_allDone.Set();
	216	}
	217	}
	218	catch (Exception e)
	219	{
	220	_allDone.Set();
	221	_asyncException = e;
	222	}
	223	}
	224
	225	/// <summary>
	226	/// Async method, invoked when the intial response if received from the server
	227	/// </summary>
	228	/// <param name="ar"></param>
	229	private void ResponseIsReadyDelegate(IAsyncResult ar)
	230	{
	231	try
	232	{
	233	// grab response
	234	WebRequest wr = (WebRequest)ar.AsyncState;
	235	_response = (HttpWebResponse)wr.EndGetResponse(ar);
	236
	237	// get response stream, and setup async reading
	238	Stream s = _response.GetResponseStream();
	239	IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s);
	240
	241	// TODO! Implement timeout, without killing the server
	242	// wait until completed, or we timed out
	243	// ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
	244	}
	245	catch (Exception e)
	246	{
	247	_allDone.Set();
	248	_asyncException = e;
	249	}
	250	}
	251
	252	// Abort the request if the timer fires.
	253	private static void TimeoutCallback(object state, bool timedOut)
	254	{
	255	if (timedOut)
	256	{
	257	HttpWebRequest request = state as HttpWebRequest;
	258	if (request != null)
	259	{
	260	request.Abort();
	261	}
	262	}
	263	}
	264
	265	/// <summary>
	266	/// Perform synchroneous request
	267	/// </summary>
	268	public Stream Request()
	269	{
	270	_request = (HttpWebRequest)WebRequest.Create(buildUri());
	271	_request.KeepAlive = false;
	272	_request.ContentType = "text/html";
	273	_request.Timeout = 200;
	274	_asyncException = null;
	275
	276	IAsyncResult responseAsyncResult = _request.BeginGetResponse(new AsyncCallback(ResponseIsReadyDelegate), _request);
	277
	278	// TODO! Implement timeout, without killing the server
	279	// this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
	280	//ThreadPool.RegisterWaitForSingleObject(responseAsyncResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true);
	281
	282	_allDone.WaitOne();
	283	if(_response != null)
	284	_response.Close();
	285	if (_asyncException != null)
	286	throw _asyncException;
	287	return _resource;
	288	}
	289
	290	#region Async Invocation
	291	public IAsyncResult BeginRequest(AsyncCallback callback, object state)
	292	{
	293	/// <summary>
	294	/// In case, we are invoked asynchroneously this object will keep track of the state
	295	/// </summary>
	296	AsyncResult<Stream> ar = new AsyncResult<Stream>(callback, state);
	297	ThreadPool.QueueUserWorkItem(RequestHelper, ar);
	298	return ar;
	299	}
	300
	301	public Stream EndRequest(IAsyncResult asyncResult)
	302	{
	303	AsyncResult<Stream> ar = (AsyncResult<Stream>)asyncResult;
	304
	305	// Wait for operation to complete, then return result or
	306	// throw exception
	307	return ar.EndInvoke();
	308	}
	309
	310	private void RequestHelper(Object asyncResult)
	311	{
	312	// We know that it's really an AsyncResult<DateTime> object
	313	AsyncResult<Stream> ar = (AsyncResult<Stream>)asyncResult;
	314	try
	315	{
	316	// Perform the operation; if sucessful set the result
	317	Stream s = Request();
	318	ar.SetAsCompleted(s, false);
	319	}
	320	catch (Exception e)
	321	{
	322	// If operation fails, set the exception
	323	ar.HandleException(e, false);
	324	}
	325	}
	326	#endregion Async Invocation
	327	}
	328	}