Add Pegen grammar for reading Python3 grammar.

pegen/CSharp/Adaptor.cs

@@ -0,0 +1,43 @@
+using Antlr4.Runtime;
+using Antlr4.Runtime.Misc;
+using System;
+using System.IO;
+using System.Reflection;
+
+public abstract class Adaptor : Lexer
+{
+    readonly ICharStream stream;
+    readonly FieldInfo tokenInput = typeof(CommonToken).GetField("_type", BindingFlags.NonPublic | BindingFlags.Instance);
+    protected Adaptor(ICharStream input)
+            : base(input, Console.Out, Console.Error)
+    {
+        stream = input;
+    }
+
+    protected Adaptor(ICharStream input, TextWriter output, TextWriter errorOutput)
+            : base(input, output, errorOutput)
+    {
+        stream = input;
+    }
+
+    private int CurrentRuleType { get; set; } = TokenConstants.InvalidType;
+
+    public bool AtEnd()
+    {
+        return CurrentMode == pegen_v3_10Lexer.ACTION_MODE;
+    }
+
+    protected void handleEndAction()
+    {
+        int oldMode = CurrentMode;
+        int newMode = PopMode();
+        bool isActionWithinAction = ModeStack.Count > 0
+            && newMode == pegen_v3_10Lexer.ACTION_MODE
+            && oldMode == newMode;
+
+        if (isActionWithinAction)
+        {
+            CurrentRuleType = (pegen_v3_10Lexer.ACTION);
+        }
+    }
+}

pegen/Java/Adaptor.java

@@ -0,0 +1,31 @@
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.Lexer;
+import org.antlr.v4.runtime.Token;
+
+public abstract class Adaptor extends Lexer {
+
+    protected Adaptor(CharStream input) {
+	super(input);
+    }
+
+    private int CurrentRuleType = Token.INVALID_TYPE;
+
+    public boolean AtEnd()
+    {
+	return this._mode == pegen_v3_10Lexer.ACTION_MODE;
+    }
+
+    protected void handleEndAction()
+    {
+	int oldMode = this._mode;
+	int newMode = this.popMode();
+	boolean isActionWithinAction = !this._modeStack.isEmpty()
+				    && newMode == pegen_v3_10Lexer.ACTION_MODE
+				    && oldMode == newMode;
+
+	if (isActionWithinAction)
+	{
+	    CurrentRuleType = (pegen_v3_10Lexer.ACTION);
+	}
+    }
+}

pegen/desc.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<desc xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../_scripts/desc.xsd">
+   <targets>CSharp;Java</targets>
+</desc>