From a3fba29ef97eb77ac33f4f1f52f927513a6aee92 Mon Sep 17 00:00:00 2001
From: alcexhim <alcexhim@gmail.com>
Date: Thu, 23 Jul 2015 10:03:48 -0400
Subject: [PATCH] Added ability to arbitrarily get data from a File by offset
 and length (without having to read the ENTIRE file from the source data);
 this must be supported by your DataFormat's implementation of DataRequest
 though

---
 .../FileSystem/DataRequestEvent.cs            | 22 ++++++++----
 .../ObjectModels/FileSystem/File.cs           | 36 ++++++++++++++++++-
 2 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/DataRequestEvent.cs b/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/DataRequestEvent.cs
index 3335c2e8..afd736cf 100644
--- a/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/DataRequestEvent.cs
+++ b/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/DataRequestEvent.cs
@@ -2,13 +2,23 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using UniversalEditor.IO;
 
 namespace UniversalEditor.ObjectModels.FileSystem
 {
-    public delegate void DataRequestEventHandler(object sender, DataRequestEventArgs e);
-    public class DataRequestEventArgs : EventArgs
-    {
-        private byte[] mvarData = null;
-        public byte[] Data { get { return mvarData; } set { mvarData = value; } }
-    }
+	public delegate void DataRequestEventHandler(object sender, DataRequestEventArgs e);
+	public class DataRequestEventArgs : EventArgs
+	{
+		private byte[] mvarData = null;
+		public byte[] Data { get { return mvarData; } set { mvarData = value; } }
+
+		private Reader mvarReader = null;
+		public Reader Reader { get { return mvarReader; } set { mvarReader = value; } }
+
+		private long mvarOffset = 0;
+		public long Offset { get { return mvarOffset; } set { mvarOffset = value; } }
+
+		private long mvarLength = 0;
+		public long Length { get { return mvarLength; } set { mvarLength = value; } }
+	}
 }
diff --git a/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/File.cs b/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/File.cs
index f5616fa8..3b942479 100644
--- a/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/File.cs
+++ b/CSharp/Plugins/UniversalEditor.Essential/ObjectModels/FileSystem/File.cs
@@ -99,7 +99,18 @@ namespace UniversalEditor.ObjectModels.FileSystem
 			{
 				DataRequestEventArgs e = new DataRequestEventArgs();
 				DataRequest(this, e);
-				mvarData = e.Data;
+				if (e.Data == null && e.Reader == null)
+				{
+					Console.WriteLine("DataRequest: " + mvarName + ": Data is not represented as a byte array or Reader");
+				}
+				else if (e.Data != null)
+				{
+					mvarData = e.Data;
+				}
+				else
+				{
+					Console.WriteLine("DataRequest: " + mvarName + ": Data is not represented as a byte array; please use GetData() method");
+				}
 			}
 			return mvarData;
 		}
@@ -109,6 +120,29 @@ namespace UniversalEditor.ObjectModels.FileSystem
 			mvarData = data;
 		}
 
+		public byte[] GetData(long offset, long length)
+		{
+			DataRequestEventArgs e = new DataRequestEventArgs();
+			DataRequest(this, e);
+			if (e.Data != null)
+			{
+				long realLength = Math.Min(length, e.Data.Length);
+				byte[] data = new byte[realLength];
+				Array.Copy(e.Data, 0, data, 0, realLength);
+				return data;
+			}
+			else if (e.Reader != null)
+			{
+				long realLength = Math.Min(length, e.Length);
+				e.Reader.Seek(e.Offset + offset, IO.SeekOrigin.Begin);
+				byte[] data = e.Reader.ReadBytes(length);
+				return data;
+			}
+
+			Console.WriteLine("DataRequest: " + mvarName + ": Data is not represented as a byte array or Reader");
+			return null;
+		}
+
 		private System.IO.Stream mvarStream = null;
 		public System.IO.Stream GetDataAsStream()
 		{