78 lines
3.3 KiB
C#
78 lines
3.3 KiB
C#
using Age.Engine.Model;
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namespace Age.Engine.Sys4;
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public static class Sys4Loader
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{
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private const int HeaderSize = 0x3C, BodyOff = 0x3C, NumFields = 13, ArrayOpcode = 0x64;
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public static Script Load(string path, OpcodeTable table)
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=> Parse(File.ReadAllBytes(path), table, Path.GetFileName(path));
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public static Script Parse(byte[] data, OpcodeTable table, string name = "")
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{
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if (data.Length < HeaderSize) throw new InvalidDataException($"{name}: too small");
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if (!(data[0] == (byte)'S' && data[1] == (byte)'Y' && data[2] == (byte)'S' && data[3] == (byte)'4'))
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throw new InvalidDataException($"{name}: bad magic");
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if (data.Length % 4 != 0) throw new InvalidDataException($"{name}: not dword-aligned");
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var fields = new int[NumFields];
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for (int k = 0; k < NumFields; k++) fields[k] = BitConverter.ToInt32(data, 8 + k * 4);
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int nbody = (data.Length - BodyOff) / 4;
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var dw = new uint[nbody];
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for (int k = 0; k < nbody; k++) dw[k] = BitConverter.ToUInt32(data, BodyOff + k * 4);
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var header = new ScriptHeader(fields[0], fields[1], fields[2], fields[3], fields[4], fields[5]);
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var (instrs, idxByOff, strings) = DecodeCode(dw, fields, nbody, table);
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return new Script
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{
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Name = name,
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Header = header,
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Instructions = instrs,
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IndexByOffset = idxByOff,
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Strings = strings,
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BodyDwords = dw,
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};
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}
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private static (List<Instruction>, Dictionary<int, int>, Dictionary<int, string>)
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DecodeCode(uint[] dw, int[] fields, int nbody, OpcodeTable table)
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{
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int codeEnd = fields[8]; // F8; shrinks to first inline string/array offset
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var instrs = new List<Instruction>();
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var idx = new Dictionary<int, int>();
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var strings = new Dictionary<int, string>();
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int i = 0;
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while (i < codeEnd)
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{
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int op = (int)dw[i];
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int argc = table.Argc(op);
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if (argc < 0) { idx[i] = instrs.Count; instrs.Add(new Instruction(i, op, Array.Empty<Operand>())); break; }
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int baseI = i + 1;
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if (baseI + 2 * argc > codeEnd) { idx[i] = instrs.Count; instrs.Add(new Instruction(i, op, Array.Empty<Operand>())); break; }
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var args = new Operand[argc];
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for (int a = 0; a < argc; a++)
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{
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int atype = (int)dw[baseI + 2 * a];
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long aval = dw[baseI + 2 * a + 1];
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args[a] = new Operand(atype, aval);
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if (atype == 2 && aval >= 0 && aval < nbody)
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{
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if (aval < codeEnd) codeEnd = (int)aval;
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if (!strings.ContainsKey((int)aval))
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{
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var (text, _) = Sys4StringCodec.Decode(dw, (int)aval);
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if (text != null) strings[(int)aval] = text;
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}
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}
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else if (op == ArrayOpcode && a == 1 && aval >= 0 && aval < nbody)
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{
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if (aval < codeEnd) codeEnd = (int)aval;
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}
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}
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idx[i] = instrs.Count;
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instrs.Add(new Instruction(i, op, args));
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i = baseI + 2 * argc;
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}
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return (instrs, idx, strings);
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}
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}
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