add/group extensions to parse strings

csharp/Lib/Utils/StringParsing.cs

@@ -0,0 +1,87 @@
+using System.Reactive.Linq;
+using System.Text;
+
+namespace InnovEnergy.Lib.Utils;
+
+public static class StringParsing
+{
+    public static IObservable<String> ParseLines(this IObservable<ReadOnlyMemory<Byte>> source, String eol = "\n")
+    {
+        return ParseLines(source, Encoding.UTF8, eol);
+    }
+
+    public static IObservable<String> ParseLines(this IObservable<ReadOnlyMemory<Byte>> source, Encoding encoding, String eol = "\n")
+    {
+        return source
+              .Select(d => encoding.GetString(d.Span))
+              .ParseLines(eol);
+    }
+
+    public static IObservable<String> ParseLines(this IObservable<String> source, String eol = "\n")
+    {
+        var accumulator = new StringBuilder();
+         
+        return source
+              .Append(eol)
+              .SelectMany(SplitLines);
+         
+        IEnumerable<String> SplitLines(String s)
+        {
+            if (!s.Contains(eol))
+            {
+                accumulator.Append(s);
+                yield break;
+            }
+    
+            var split = s.Split(eol); // scatter
+    
+            yield return accumulator.Append(split[0]).ToString(); // gather    
+          
+            foreach (var line in split[1..^1])
+                yield return line;
+            
+            accumulator.Clear();
+            accumulator.Append(split[^1]);
+        }        
+    }
+
+    public static IEnumerable<String> ParseLines(this IEnumerable<ReadOnlyMemory<Byte>> source, String eol = "\n")
+    {
+        return ParseLines(source, Encoding.UTF8, eol);
+    }
+
+    public static IEnumerable<String> ParseLines(this IEnumerable<ReadOnlyMemory<Byte>> source, Encoding encoding, String eol = "\n")
+    {
+        return source
+              .Select(d => encoding.GetString(d.Span))
+              .ParseLines(eol);
+    }
+
+    public static IEnumerable<String> ParseLines(this IEnumerable<String> source, String eol = "\n")
+    {
+        var accumulator = new StringBuilder();
+         
+        return source
+              .Append(eol)
+              .SelectMany(SplitLines);
+         
+        IEnumerable<String> SplitLines(String s)
+        {
+            if (!s.Contains(eol))
+            {
+                accumulator.Append(s);
+                yield break;
+            }
+    
+            var split = s.Split(eol); // scatter
+    
+            yield return accumulator.Append(split[0]).ToString(); // gather    
+          
+            foreach (var line in split[1..^1])
+                yield return line;
+            
+            accumulator.Clear();
+            accumulator.Append(split[^1]);
+        }        
+    }
+}