replaced ReadByte with 64kb buffer in parser

ParadoxSaveParser.Lib/SaveParserEU4.cs

@@ -1,4 +1,4 @@
-global using System;
+global using System;
 global using System.Collections.Generic;
 global using System.IO;
 global using System.Text;
@@ -80,17 +80,19 @@ public class SaveParserEU4
             return true;
         }
 
-        while (_saveFile.CanRead)
+        // Reading the save one byte at a time through Stream.ReadByte() costs a virtual call
+        // per byte, which dominated the parsing time. Bytes are pulled into this buffer
+        // instead, so the stream is touched once per 64 KB and the inner loop reads an array.
+        byte[] buffer = new byte[64 * 1024];
+        int bufferLength;
+        while ((bufferLength = _saveFile.Read(buffer, 0, buffer.Length)) > 0)
         {
-            int c = _saveFile.ReadByte();
+            for (int i = 0; i < bufferLength; i++)
+            {
+                int c = buffer[i];
                 column++;
                 switch (c)
                 {
-                case -1:
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    _stringBuilderPool.Return(strb);
-                    yield break;
                     case '\"':
                         isQuoteOpen = !isQuoteOpen;
                         isStrInQuotes = true;
@@ -142,7 +144,11 @@ public class SaveParserEU4
                         break;
                 }
             }
+        }
 
+        // end of file: the last token may still be unterminated
+        if (TryCompleteStringToken())
+            yield return strToken;
         _stringBuilderPool.Return(strb);
     }