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feat(a1): SYS4 container parser (header + code decode + data_array_end shrink)

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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
gamer147
2026-07-06 13:51:32 -04:00
parent f3fe8ffe58
commit 0cb83fcb62
2 changed files with 91 additions and 0 deletions
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69
engine/Age.Engine/Sys4/Sys4Loader.cs Normal file
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using Age.Engine.Model;
namespace Age.Engine.Sys4;
public static class Sys4Loader
{
private const int HeaderSize = 0x3C, BodyOff = 0x3C, NumFields = 13, ArrayOpcode = 0x64;
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 = "")
{
if (data.Length < HeaderSize) throw new InvalidDataException($"{name}: too small");
if (!(data[0] == (byte)'S' && data[1] == (byte)'Y' && data[2] == (byte)'S' && data[3] == (byte)'4'))
throw new InvalidDataException($"{name}: bad magic");
if (data.Length % 4 != 0) throw new InvalidDataException($"{name}: not dword-aligned");
var fields = new int[NumFields];
for (int k = 0; k < NumFields; k++) fields[k] = BitConverter.ToInt32(data, 8 + k * 4);
int nbody = (data.Length - BodyOff) / 4;
var dw = new uint[nbody];
for (int k = 0; k < nbody; k++) dw[k] = BitConverter.ToUInt32(data, BodyOff + k * 4);
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);
return new Script { Header = header, Instructions = instrs, IndexByOffset = idxByOff, Strings = strings };
}
private static (List<Instruction>, Dictionary<int, int>, Dictionary<int, string>)
DecodeCode(uint[] dw, int[] fields, int nbody, OpcodeTable table)
{
int codeEnd = fields[8]; // F8; shrinks to first inline string/array offset
var instrs = new List<Instruction>();
var idx = new Dictionary<int, int>();
var strings = new Dictionary<int, string>();
int i = 0;
while (i < codeEnd)
{
int op = (int)dw[i];
int argc = table.Argc(op);
if (argc < 0) { idx[i] = instrs.Count; instrs.Add(new Instruction(i, op, Array.Empty<Operand>())); break; }
int baseI = i + 1;
if (baseI + 2 * argc > codeEnd) { idx[i] = instrs.Count; instrs.Add(new Instruction(i, op, Array.Empty<Operand>())); break; }
var args = new Operand[argc];
for (int a = 0; a < argc; a++)
{
int atype = (int)dw[baseI + 2 * a];
long aval = dw[baseI + 2 * a + 1];
args[a] = new Operand(atype, aval);
if (atype == 2 && aval >= 0 && aval < nbody)
{
if (aval < codeEnd) codeEnd = (int)aval;
if (!strings.ContainsKey((int)aval))
{
var (text, _) = Sys4StringCodec.Decode(dw, (int)aval);
if (text != null) strings[(int)aval] = text;
}
}
else if (op == ArrayOpcode && a == 1 && aval >= 0 && aval < nbody)
{
if (aval < codeEnd) codeEnd = (int)aval;
}
}
idx[i] = instrs.Count;
instrs.Add(new Instruction(i, op, args));
i = baseI + 2 * argc;
}
return (instrs, idx, strings);
}
}