Flee

Parsing/AlternativeElement.cs

@@ -0,0 +1,60 @@
+namespace Flee.Parsing
+{
+    /**
+      * A regular expression alternative element. This element matches
+      * the longest alternative element.
+      */
+    internal class AlternativeElement : Element
+    {
+        private readonly Element _elem1;
+        private readonly Element _elem2;
+
+        public AlternativeElement(Element first, Element second)
+        {
+            _elem1 = first;
+            _elem2 = second;
+        }
+
+        public override object Clone()
+        {
+            return new AlternativeElement(_elem1, _elem2);
+        }
+
+        public override int Match(Matcher m,
+                                  ReaderBuffer buffer,
+                                  int start,
+                                  int skip)
+        {
+            int length = 0;
+            int length1 = -1;
+            int length2 = -1;
+            int skip1 = 0;
+            int skip2 = 0;
+
+            while (length >= 0 && skip1 + skip2 <= skip)
+            {
+                length1 = _elem1.Match(m, buffer, start, skip1);
+                length2 = _elem2.Match(m, buffer, start, skip2);
+                if (length1 >= length2)
+                {
+                    length = length1;
+                    skip1++;
+                }
+                else
+                {
+                    length = length2;
+                    skip2++;
+                }
+            }
+            return length;
+        }
+
+        public override void PrintTo(TextWriter output, string indent)
+        {
+            output.WriteLine(indent + "Alternative 1");
+            _elem1.PrintTo(output, indent + "  ");
+            output.WriteLine(indent + "Alternative 2");
+            _elem2.PrintTo(output, indent + "  ");
+        }
+    }
+}