source code checkin

src/ArkData/Extensions.cs

@@ -0,0 +1,58 @@
+using System.Collections.Generic;
+
+namespace ArkData
+{
+    internal static class Extensions
+    {
+        private static readonly int[] Empty = new int[0];
+
+        public static int LocateFirst(this byte[] self, byte[] candidate, int offset = 0)
+        {
+            if (IsEmptyLocate(self, candidate, offset))
+                return -1;
+
+            for (int position = offset; position < self.Length; position++)
+                if (IsMatch(self, position, candidate))
+                    return position;
+     
+            return -1;
+        }
+
+        public static int[] Locate(this byte[] self, byte[] candidate)
+        {
+            if (IsEmptyLocate(self, candidate, 0))
+                return Empty;
+
+            List<int> list = new List<int>();
+            for (int position = 0; position < self.Length; ++position)
+                if (IsMatch(self, position, candidate))
+                    list.Add(position);
+
+            if (list.Count != 0)
+                return list.ToArray();
+
+            return Empty;
+        }
+
+        private static bool IsMatch(byte[] array, int position, byte[] candidate)
+        {
+            if (candidate.Length > array.Length - position)
+                return false;
+
+            for (int index = 0; index < candidate.Length; ++index)
+                if ((array[position + index] != candidate[index]))
+                    return false;
+
+            return true;
+        }
+
+        private static bool IsEmptyLocate(byte[] array, byte[] candidate, int offset)
+        {
+            if (array != null && candidate != null &&
+               (array.Length != 0 && candidate.Length != 0) &&
+               (candidate.Length <= array.Length && offset != -1))
+                return offset > array.Length;
+            return true;
+        }
+    }
+}