Ram Search - use binary search to grealtly speed up preview when scrolling deep into the list

BizHawk.MultiClient/tools/Watch/RamSearchEngine.cs

@@ -8,8 +8,47 @@ using System.Threading.Tasks;
 
 namespace BizHawk.MultiClient
 {
+	//TODO: move me
+	//http://stackoverflow.com/questions/1766328/can-linq-use-binary-search-when-the-collection-is-ordered
+	public static class BinarySearchClass
+	{
+		public static T BinarySearch<T, TKey>(this IList<T> list, Func<T, TKey> keySelector, TKey key)
+		where TKey : IComparable<TKey>
+		{
+			int min = 0;
+			int max = list.Count;
+			while (min < max)
+			{
+				int mid = (max + min) / 2;
+				T midItem = list[mid];
+				TKey midKey = keySelector(midItem);
+				int comp = midKey.CompareTo(key);
+				if (comp < 0)
+				{
+					min = mid + 1;
+				}
+				else if (comp > 0)
+				{
+					max = mid - 1;
+				}
+				else
+				{
+					return midItem;
+				}
+			}
+			if (min == max &&
+				keySelector(list[min]).CompareTo(key) == 0)
+			{
+				return list[min];
+			}
+			throw new InvalidOperationException("Item not found");
+		}
+	}
+
 	public class RamSearchEngine
 	{
+		
+
 		public enum ComparisonOperator { Equal, GreaterThan, GreaterThanEqual, LessThan, LessThanEqual, NotEqual, DifferentBy };
 		public enum Compare { Previous, SpecificValue, SpecificAddress, Changes, Difference }
 		
@@ -175,7 +214,11 @@ namespace BizHawk.MultiClient
 
 		public bool Preview(int address)
 		{
-			var listOfOne = new List<IMiniWatch>() { _watchList.FirstOrDefault(x => x.Address == address) };
+			var listOfOne = new List<IMiniWatch>
+			{
+				_watchList.BinarySearch(x => x.Address, address)
+			};
+
 			switch (_compareTo)
 			{
 				default: