From f1aca261ae08c99f94ac4aa9babe9b33d0c2f5df Mon Sep 17 00:00:00 2001
From: Timerix <timerix11@gmail.com>
Date: Mon, 14 Sep 2026 23:09:16 +0200
Subject: [PATCH] replaced ReadByte with 64kb buffer in parser

---
 ParadoxSaveParser.Lib/SaveParserEU4.cs | 124 +++++++++++++------------
 1 file changed, 65 insertions(+), 59 deletions(-)

diff --git a/ParadoxSaveParser.Lib/SaveParserEU4.cs b/ParadoxSaveParser.Lib/SaveParserEU4.cs
index d6e07c7..2c1f431 100644
--- a/ParadoxSaveParser.Lib/SaveParserEU4.cs
+++ b/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;
@@ -80,69 +80,75 @@ 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();
-            column++;
-            switch (c)
+            for (int i = 0; i < bufferLength; i++)
             {
-                case -1:
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    _stringBuilderPool.Return(strb);
-                    yield break;
-                case '\"':
-                    isQuoteOpen = !isQuoteOpen;
-                    isStrInQuotes = true;
-                    break;
-                case ' ':
-                case '\t':
-                case '\r':
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    break;
-                case '\n':
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    line++;
-                    column = 0;
-                    break;
-                case '=':
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    yield return new Token
-                    {
-                        type = TokenType.Equals,
-                        line = line, column = (short)column
-                    };
-                    break;
-                case '{':
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    yield return new Token
-                    {
-                        type = TokenType.BracketOpen,
-                        line = line, column = (short)column
-                    };
-                    break;
-                case '}':
-                    if (TryCompleteStringToken())
-                        yield return strToken;
-                    yield return new Token
-                    {
-                        type = TokenType.BracketClose,
-                        line = line, column = (short)column
-                    };
-                    break;
-                default:
-                    // Skip control characters, which are invisible and causing frontend bugs.
-                    // I dont know why there are so many of them in strings.
-                    if (c >= 0x20)
-                        strb.Append((char)c);
-                    break;
+                int c = buffer[i];
+                column++;
+                switch (c)
+                {
+                    case '\"':
+                        isQuoteOpen = !isQuoteOpen;
+                        isStrInQuotes = true;
+                        break;
+                    case ' ':
+                    case '\t':
+                    case '\r':
+                        if (TryCompleteStringToken())
+                            yield return strToken;
+                        break;
+                    case '\n':
+                        if (TryCompleteStringToken())
+                            yield return strToken;
+                        line++;
+                        column = 0;
+                        break;
+                    case '=':
+                        if (TryCompleteStringToken())
+                            yield return strToken;
+                        yield return new Token
+                        {
+                            type = TokenType.Equals,
+                            line = line, column = (short)column
+                        };
+                        break;
+                    case '{':
+                        if (TryCompleteStringToken())
+                            yield return strToken;
+                        yield return new Token
+                        {
+                            type = TokenType.BracketOpen,
+                            line = line, column = (short)column
+                        };
+                        break;
+                    case '}':
+                        if (TryCompleteStringToken())
+                            yield return strToken;
+                        yield return new Token
+                        {
+                            type = TokenType.BracketClose,
+                            line = line, column = (short)column
+                        };
+                        break;
+                    default:
+                        // Skip control characters, which are invisible and causing frontend bugs.
+                        // I dont know why there are so many of them in strings.
+                        if (c >= 0x20)
+                            strb.Append((char)c);
+                        break;
+                }
             }
         }
 
+        // end of file: the last token may still be unterminated
+        if (TryCompleteStringToken())
+            yield return strToken;
         _stringBuilderPool.Return(strb);
     }