Add guards against empy spans

Author: mythz

src/ServiceStack.Text/CharMemoryExtensions.cs

@@ -388,6 +388,7 @@ public static ReadOnlyMemory<char> Trim(this ReadOnlyMemory<char> span)
 
         public static ReadOnlyMemory<char> TrimStart(this ReadOnlyMemory<char> value)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringMemory;
             var span = value.Span;
             int start = 0;
             for (; start < span.Length; start++)
@@ -400,6 +401,7 @@ public static ReadOnlyMemory<char> TrimStart(this ReadOnlyMemory<char> value)
 
         public static ReadOnlyMemory<char> TrimEnd(this ReadOnlyMemory<char> value)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringMemory;
             var span = value.Span;
             int end = span.Length - 1;
             for (; end >= 0; end--)
@@ -425,9 +427,10 @@ public static ReadOnlyMemory<char> SafeSlice(this ReadOnlyMemory<char> value, in
 
         public static string SubstringWithEllipsis(this ReadOnlyMemory<char> value, int startIndex, int length)
         {
+            if (value.IsEmpty) return string.Empty;
             var str = value.Slice(startIndex, length);
             return str.Length == length
-                ? str.ToString() + "..."
+                ? str + "..."
                 : str.ToString();
         }
 

src/ServiceStack.Text/StringSpanExtensions.cs

@@ -459,13 +459,15 @@ public static ReadOnlySpan<char> ParentDirectory(this ReadOnlySpan<char> filePat
 
         public static ReadOnlySpan<char> TrimEnd(this ReadOnlySpan<char> value, params char[] trimChars)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringSpan;
             if (trimChars == null || trimChars.Length == 0)
                 return value.TrimHelper(1);
             return value.TrimHelper(trimChars, 1);
         }
 
         private static ReadOnlySpan<char> TrimHelper(this ReadOnlySpan<char> value, int trimType)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringSpan;
             int end = value.Length - 1;
             int start = 0;
             if (trimType != 1)
@@ -485,6 +487,7 @@ private static ReadOnlySpan<char> TrimHelper(this ReadOnlySpan<char> value, int
 
         private static ReadOnlySpan<char> TrimHelper(this ReadOnlySpan<char> value, char[] trimChars, int trimType)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringSpan;
             int end = value.Length - 1;
             int start = 0;
             if (trimType != 1)
@@ -516,6 +519,7 @@ private static ReadOnlySpan<char> TrimHelper(this ReadOnlySpan<char> value, char
 
         private static ReadOnlySpan<char> CreateTrimmedString(this ReadOnlySpan<char> value, int start, int end)
         {
+            if (value.IsEmpty) return TypeConstants.NullStringSpan;
             int length = end - start + 1;
             if (length == value.Length)
                 return value;
@@ -539,6 +543,7 @@ public static ReadOnlySpan<char> SafeSlice(this ReadOnlySpan<char> value, int st
 
         public static string SubstringWithEllipsis(this ReadOnlySpan<char> value, int startIndex, int length)
         {
+            if (value.IsEmpty) return string.Empty;
             var str = value.Slice(startIndex, length);
             return str.Length == length
                 ? str.ToString() + "..."
@@ -656,6 +661,5 @@ public static int CountOccurrencesOf(this ReadOnlySpan<char> value, char needle)
             }
             return count;
         }
-
     }
 }