added options

Author: dragon7307

src/CountExceedingBehaviour.cs

@@ -0,0 +1,17 @@
+namespace SpanExtensions
+{
+    /// <summary>
+    /// Defines the behaviour of a split operation when there are more split instances than there may be. 
+    /// </summary> 
+    public enum CountExceedingBehaviour
+    {
+        /// <summary>
+        /// The last element returned will be all the remaining elements appended as one.
+        /// </summary>
+        AppendLastElements,
+        /// <summary>
+        /// Every split instance more than permitted will not be returned. 
+        /// </summary> 
+        CutLastElements
+    }
+}

src/Enumerators/Split/SpanSplitWithCountEnumerator.cs

@@ -6,12 +6,14 @@ namespace SpanExtensions.Enumerators
     /// Supports iteration over a <see cref="ReadOnlySpan{T}"/> by splitting it a a specified delimiter of type <typeparamref name="T"/> with an upper limit of splits performed.
     /// </summary>
     /// <typeparam name="T">The type of elements in the enumerated <see cref="ReadOnlySpan{T}"/>.</typeparam>
-    public ref struct SpanSplitWithCountEnumerator<T> where T : IEquatable<T>
+    public ref struct SpanSplitWithCountEnumerator<T> where T : IEquatable<T> 
     {
         ReadOnlySpan<T> Span;
         readonly T Delimiter;
         readonly int Count;
+        readonly CountExceedingBehaviour CountExceedingBehaviour; 
         int currentCount;
+        readonly int CountMinusOne;
 
         /// <summary>
         /// Gets the element in the collection at the current position of the enumerator.
@@ -24,13 +26,16 @@ namespace SpanExtensions.Enumerators
         /// <param name="source">The <see cref="ReadOnlySpan{T}"/> to be split.</param>
         /// <param name="delimiter">An instance of <typeparamref name="T"/> that delimits the various sub-ReadOnlySpans in <paramref name="source"/>.</param>
         /// <param name="count">The maximum number of sub-ReadOnlySpans to split into.</param>
-        public SpanSplitWithCountEnumerator(ReadOnlySpan<T> source, T delimiter, int count)
+        /// <param name="countExceedingBehaviour">The handling of the instances more than count.</param>
+        public SpanSplitWithCountEnumerator(ReadOnlySpan<T> source, T delimiter, int count, CountExceedingBehaviour countExceedingBehaviour = CountExceedingBehaviour.CutLastElements)
         {
             Span = source;
             Delimiter = delimiter;
             Count = count;
+            CountExceedingBehaviour = countExceedingBehaviour;
             Current = default;
             currentCount = 0;
+            CountMinusOne = Math.Max(Count - 1, 0);
         }
 
         /// <summary>
@@ -57,6 +62,26 @@ public bool MoveNext()
                 return false;
             }
             int index = span.IndexOf(Delimiter);
+            switch(CountExceedingBehaviour)
+            {
+                case CountExceedingBehaviour.CutLastElements:
+                    break; 
+                case CountExceedingBehaviour.AppendLastElements:
+                    if(currentCount == CountMinusOne) 
+                    {
+                        ReadOnlySpan<T> lower  = span[..index]; 
+                        ReadOnlySpan<T> upper = span[(index + 1)..]; 
+                        Span<T> temp = new T[lower.Length + upper.Length];  
+                        lower.CopyTo(temp[..index]); 
+                        upper.CopyTo(temp[index..]);
+                        Current = temp;  
+                        currentCount++;
+                        return true; 
+                    }
+                    break;
+                default:
+                    throw new InvalidCountExceedingBehaviourException(CountExceedingBehaviour);
+            }
             if(index == -1 || index >= span.Length)
             {
                 Span = ReadOnlySpan<T>.Empty;
@@ -69,4 +94,4 @@ public bool MoveNext()
             return true;
         }
     }
-}
+}

src/Extensions/ReadOnlySpan/ReadOnlySpanExtensions.String.cs

@@ -1,5 +1,4 @@
-
-using System;
+using System;
 
 namespace SpanExtensions
 {

src/InvalidCountExceedingBehaviourException.cs

@@ -0,0 +1,43 @@
+using System;
+
+namespace SpanExtensions
+{
+    /// <summary>
+    /// The Exception that is thrown for an undefined enumeration value of <see cref="CountExceedingBehaviour"/>.
+    /// </summary>
+    [Serializable]
+    public class InvalidCountExceedingBehaviourException : Exception
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="InvalidCountExceedingBehaviourException"/> class with a system-supplied message.
+        /// </summary>
+        /// <param name="countExceedingBehaviour"> The invalid <see cref="CountExceedingBehaviour"/>.  </param>
+        public InvalidCountExceedingBehaviourException(CountExceedingBehaviour countExceedingBehaviour) :
+            base($"CountExceedingBehaviour with ID '{(int) countExceedingBehaviour} is not defined. CountExceedingBehaviour only defines {GetCountExceedingBehaviourNamesListed()}.")
+        {
+            
+        }
+
+        static string GetCountExceedingBehaviourNamesListed()
+        {
+            string[] countExceedingBehaviourNames = Array.Empty<string>();
+#if NET5_0_OR_GREATER
+            countExceedingBehaviourNames = Enum.GetNames<CountExceedingBehaviour>();
+#else
+            countExceedingBehaviourNames = (string[]) Enum.GetNames(typeof(CountExceedingBehaviour));
+#endif
+            switch(countExceedingBehaviourNames.Length)
+            {
+                case 0:
+                    return "";
+                case 1:
+                    return countExceedingBehaviourNames[0];
+                default:
+                    string first = countExceedingBehaviourNames[0]; 
+                    string end = string.Join(',', countExceedingBehaviourNames, 1, countExceedingBehaviourNames.Length - 1);
+                    return $"{first} and {end}";
+            }
+
+        }
+    }
+}