Implement native RT.DAT read history

engine/Age.Engine/Sys4/ScriptAssembler.cs

@@ -28,13 +28,20 @@ public static class ScriptAssembler
     {
         int codeLen = 0;
         foreach (var ins in instrs) codeLen += 1 + 2 * ins.Args.Length;
+        var messageOffsets = new List<uint>();
+        int instructionOffset = 0;
+        foreach (var ins in instrs)
+        {
+            if (ins.Op == 0x71) messageOffsets.Add((uint)instructionOffset);
+            instructionOffset += 1 + 2 * ins.Args.Length;
+        }
 
         // Encode strings; record each string's starting dword offset (relative to body start).
         var strDwords = new List<uint>();
         var strOffset = new int[strings.Count];
         for (int i = 0; i < strings.Count; i++)
         {
-            strOffset[i] = codeLen + strDwords.Count;
+            strOffset[i] = codeLen + messageOffsets.Count + strDwords.Count;
             strDwords.AddRange(EncodeString(strings[i]));
         }
 
@@ -49,10 +56,14 @@ public static class ScriptAssembler
                 body.Add((uint)val);
             }
         }
+        body.AddRange(messageOffsets);
         body.AddRange(strDwords);
 
         var fields = new int[NumFields];
-        fields[8] = codeLen;                       // F8 = code end (strings begin here)
+        fields[7] = messageOffsets.Count;            // F7 = T1/read-message boundary count
+        fields[8] = codeLen;                       // F8 = code end / T1 table start
+        fields[10] = codeLen + messageOffsets.Count;
+        fields[12] = codeLen + messageOffsets.Count;
 
         var bytes = new byte[HeaderSize + body.Count * 4];
         Encoding.ASCII.GetBytes("SYS4422 ").CopyTo(bytes, 0);

engine/Age.Engine/Sys4/Sys4Loader.cs

@@ -7,7 +7,7 @@ public static class Sys4Loader
     public static Script Load(string path, OpcodeTable table)
         => Parse(File.ReadAllBytes(path), table, Path.GetFileName(path));
 
-    public static Script Parse(byte[] data, OpcodeTable table, string name = "")
+    public static Script Parse(byte[] data, OpcodeTable table, string name = "", uint packedId = 0)
     {
         if (data.Length < HeaderSize) throw new InvalidDataException($"{name}: too small");
         if (!(data[0] == (byte)'S' && data[1] == (byte)'Y' && data[2] == (byte)'S' && data[3] == (byte)'4'))
@@ -22,14 +22,23 @@ public static class Sys4Loader
 
         var header = new ScriptHeader(fields[0], fields[1], fields[2], fields[3], fields[4], fields[5]);
         var (instrs, idxByOff, strings) = DecodeCode(dw, fields, nbody, table);
+        int messageCount = fields[7];
+        int messageTableOffset = fields[8];
+        if (messageCount < 0 || messageTableOffset < 0
+            || messageTableOffset > nbody || messageCount > nbody - messageTableOffset)
+            throw new InvalidDataException($"{name}: invalid T1 read-message table");
+        int[] messageOffsets = dw.AsSpan(messageTableOffset, messageCount)
+            .ToArray().Select(value => checked((int)value)).ToArray();
         return new Script
         {
             Name = name,
+            PackedId = packedId,
             Header = header,
             Instructions = instrs,
             IndexByOffset = idxByOff,
             Strings = strings,
             BodyDwords = dw,
+            ReadMessageOffsets = messageOffsets,
         };
     }
 

engine/Age.Engine/Sys4/Sys4ScriptProvider.cs

@@ -51,5 +51,5 @@ public sealed class Sys4ScriptProvider : IScriptProvider
         => GetByName(name) ?? throw new FileNotFoundException($"script is not in SYS4INI: {name}", name);
 
     private Script Parse(AssetEntry entry)
-        => Sys4Loader.Parse(_store.ReadAll(entry), _table, entry.Name);
+        => Sys4Loader.Parse(_store.ReadAll(entry), _table, entry.Name, unchecked((uint)entry.PackedId));
 }