Little ARM assembler in dart

armasm.dart

// By PixelToast

var src =
    "mov r0, #69\n"
    "bx lr\n"
    "ldmedeq ip!, {a3-sp}\n"
    "strbhi r13, [v2, lr, asr #3]!\n"
    "ldrls a3, [sb], sp, asr #0x14\n";

main() {
  for (var l in src.split("\n").where((e) => e != "")) {
    var x = new Instruction.decode(l);
    print(x.assemble().toRadixString(16).padLeft(8, "0") + " " + l);
  }
}

abstract class Operand {
  int assemble();
}

int ror(int x, int y) => ((x >> y) | (x << (32 - y)) & 0xFFFFFFFF);

class ImmediateOperand extends Operand {
  factory ImmediateOperand(int val) {
    var oval = val;

    if (val != val & 0xFFFFFFFF) {
      throw "Could not encode immediate 0x${val.toRadixString(16).toUpperCase()}";
    }

    for (int offset = 0; offset < 32; offset += 2) if (ror(val, offset) <= 0xFF)
      return new ImmediateOperand.direct(ror(val, offset), (16 - offset ~/ 2) % 16);

    throw "Could not encode immediate 0x${oval.toRadixString(16).toUpperCase()}";
  }

  ImmediateOperand.direct(this.imm, this.rot);

  final int imm;
  final int rot;

  int get value => (imm >> (rot * 2)) | (imm << (32 - (rot * 2))) & 0xFFFFFFFF;

  int assemble() => imm | rot << 8;
}

enum ShiftType {
  Left,
  Right,
  ARight,
  RRight,
}

const Map<String, ShiftType> kShiftTypeNames = const {
  "ASL": ShiftType.Left,
  "LSL": ShiftType.Left,
  "LSR": ShiftType.Right,
  "ASR": ShiftType.ARight,
  "ROR": ShiftType.RRight,
};

class Shift {
  Shift(this.type, this.useReg, this.v) {
    assert(v == v & (useReg ? 0xF : 0x1F));
  }

  final ShiftType type;
  final bool useReg;
  final int v;

  assemble() => v << 3 | type.index << 1 | (useReg ? 1 : 0);

  static final NO_OP = new Shift(ShiftType.Left, false, 0);
}

class RegisterOperand extends Operand {
  RegisterOperand(this.reg, [Shift shift]) : shift = shift ?? Shift.NO_OP {
    assert(reg == reg & 0xF);
  }

  final int reg;
  Shift shift;

  assemble() => shift.assemble() << 4 | reg;
}

enum CondCode {
  EQ, NE, CS, CC,
  MI, PL, VS, VC,
  HI, LS, GE, LT,
  GT, LE, AL,
}

const Map<String, int> kCondCodeStrings = const {
  "EQ": 0, "NE": 1, "CS": 2, "CC": 3,
  "MI": 4, "PL": 5, "VS": 6, "VC": 7,
  "HI": 8, "LS": 9, "GE": 10, "LT": 11,
  "GT": 12, "LE": 13, "AL": 14, "LO": 3,
};

enum DPInstCode {
  AND, EOR, SUB, RSB,
  ADD, ADC, SBC, SRC,
  TST, TEQ, CMP, CMN,
  ORR, MOV, BIC, MVN,
}

const List<String> kDPInstCodeStrings = const [
  "AND", "EOR", "SUB", "RSB",
  "ADD", "ADC", "SBC", "SRC",
  "TST", "TEQ", "CMP", "CMN",
  "ORR", "MOV", "BIC", "MVN",
];

class DPInst extends Instruction {
  DPInst(CondCode cond, this.op, this.setCond, this.rn, this.rd, this.operand,) : useImm = operand is ImmediateOperand, super(cond) {
    assert(rn == rn & 0xF);
    assert(rd == rd & 0xF);
  }

  final bool useImm;
  final DPInstCode op;
  final bool setCond;
  final int rn;
  final int rd;
  final Operand operand;
  RegisterOperand get oprReg => useImm ? throw new StateError("Can't access register operand") : operand;
  ImmediateOperand get oprImm => !useImm ? throw new StateError("Can't access immediate operand") : operand;

  assemble() =>
    cond.index << 28 |
    (useImm ? 1 : 0) << 25 |
    op.index << 21 |
    (setCond ? 1 : 0) << 20 |
    rn << 16 |
    rd << 12 |
    operand.assemble();
}

class Branch extends Instruction {
  Branch(CondCode cond, this.link, int offset) : offset = (offset - 8).toSigned(24).toUnsigned(24) ~/ 4, super(cond) {
    assert(offset == offset & 0xFFFFFF);
  }

  final bool link;
  final int offset;

  assemble() =>
    cond.index << 28 |
    5 << 25 |
    (link ? 1 : 0) << 24 |
    offset;
}

class BranchExchange extends Instruction {
  BranchExchange(CondCode cond, this.rn) : super(cond) {
    assert(rn == rn & 0xF);
  }

  final int rn;

  assemble() =>
    cond.index << 28 |
    0x12FFF1 << 4 |
    rn;
}

enum SourcePSR {
  CPSR,
  SPSR,
}

class MRS extends Instruction {
  MRS(CondCode cond, this.ps, this.rd) : super(cond) {
    assert(rd == rd & 0xF);
  }

  final SourcePSR ps;
  final int rd;

  assemble() =>
    cond.index << 28 |
    0x2 << 23 |
    ps.index << 22 |
    0xF << 16 |
    rd << 12;
}

class MSR extends Instruction {
  MSR(CondCode cond, this.pd, this.operand) : useImm = operand is ImmediateOperand, super(cond);

  final bool useImm;
  final SourcePSR pd;
  final Operand operand;

  assemble() =>
    cond.index << 28 |
    (useImm ? 1 : 0) << 25 |
    2 << 23 |
    pd.index << 22 |
    0x29F << 12 |
    operand.assemble();
}

const List<String> kMultiplyInstNames = const ["MUL", "MLA"];

class Multiply extends Instruction {
  Multiply(CondCode cond, this.acc, this.setCond, this.rd, this.rn, this.rs, this.rm) : super(cond) {
    assert(rd == rd & 0xF);
    assert(rn == rn & 0xF);
    assert(rs == rs & 0xF);
    assert(rm == rm & 0xF);
  }

  final bool acc;
  final bool setCond;
  final int rd;
  final int rn;
  final int rs;
  final int rm;

  assemble() =>
    cond.index << 28 |
    (acc ? 1 : 0) << 21 |
    (setCond ? 1 : 0) << 20 |
    rd << 16 |
    rn << 12 |
    rs << 8 |
    0x9 << 4 |
    rm;
}

const List<String> kMultiplyLongInstNames = const ["UMULL", "UMLAL", "SMULL", "SMLAL"];

class MultiplyLong extends Instruction {
  MultiplyLong(CondCode cond, this.sgn, this.acc, this.setCond, this.rdHi, this.rdLo, this.rs, this.rm) : super(cond) {
    assert(rdHi == rdHi & 0xF);
    assert(rdLo == rdLo & 0xF);
    assert(rs == rs & 0xF);
    assert(rm == rm & 0xF);
  }

  final bool sgn;
  final bool acc;
  final bool setCond;
  final int rdHi;
  final int rdLo;
  final int rs;
  final int rm;

  assemble() =>
    cond.index << 28 |
    1 << 23 |
    (sgn ? 1 : 0) << 22 |
    (acc ? 1 : 0) << 21 |
    (setCond? 1 : 0) << 20 |
    rdHi << 16 |
    rdLo << 12 |
    rs << 8 |
    0x9 << 4 |
    rm;
}

abstract class Offset {
  int assemble();
}

class ImmediateOffset extends Offset {
  ImmediateOffset(this.offset) {
    assert(offset == offset & 0xFFF);
  }

  final int offset;

  assemble() => offset;
}

class RegisterOffset extends Offset {
  RegisterOffset(this.shift, this.rm) {
    assert(rm == rm & 0xF);
  }

  final Shift shift;
  final int rm;

  assemble() => shift.assemble() << 4 | rm;
}

class SingleDataTransfer extends Instruction {
  SingleDataTransfer(CondCode cond, this.preIdx, this.add, this.singleByte, this.wb, this.load, this.rn, this.rd, this.offset) : isReg = offset is RegisterOffset, super(cond) {
    assert(rn == rn & 0xF);
    assert(rd == rd & 0xF);
  }

  final bool isReg;
  final bool preIdx;
  final bool add;
  final bool singleByte;
  final bool wb;
  final bool load;
  final int rn;
  final int rd;
  final Offset offset;

  assemble() =>
    cond.index << 28 |
    0x1 << 26 |
    (isReg ? 1 : 0) << 25 |
    (preIdx ? 1 : 0) << 24 |
    (add ? 1 : 0) << 23 |
    (singleByte ? 1 : 0) << 22 |
    (wb ? 1 : 0) << 21 |
    (load ? 1 : 0) << 20 |
    rn << 16 |
    rd << 12 |
    offset.assemble();
}

class HalfwordSignedDataTransfer extends Instruction {
  HalfwordSignedDataTransfer(CondCode cond, this.preIdx, this.add, this.wb, this.load, this.rn, this.rd, this.sgn, this.half, this.immOffset, this.offset) : super(cond) {
    assert(offset == offset & (immOffset ? 0xF : 0xFF));
  }

  final bool preIdx;
  final bool add;
  final bool wb;
  final bool load;
  final int rn;
  final int rd;
  final bool sgn;
  final bool half;
  final bool immOffset;
  final int offset;

  assemble() =>
    cond.index << 28 |
    (preIdx ? 1 : 0) << 24 |
    (add ? 1 : 0) << 23 |
    (immOffset ? 1 : 0) << 22 |
    (wb ? 1 : 0) << 21 |
    (load ? 1 : 0) << 20 |
    rn << 16 |
    rd << 12 |
    (offset >> 4) << 8 |
    0x1 << 7 |
    (sgn ? 1 : 0) << 6 |
    (half ? 1 : 0) << 5 |
    0x1 << 4 |
    offset & 0xF;
}

class BlockDataTransfer extends Instruction {
  BlockDataTransfer(CondCode cond, this.preIdx, this.add, this.ldPSR, this.wb, this.load, this.rn, List<int> regs) :
    regs = regs.toSet(), super(cond) {
    assert(rn == rn & 0xF);
    for (var r in regs) assert(r == r & 0xF);
  }

  final bool preIdx;
  final bool add;
  final bool ldPSR;
  final bool wb;
  final bool load;
  final int rn;
  final Set<int> regs;

  assemble() =>
    cond.index << 28 |
    0x4 << 25 |
    (preIdx ? 1 : 0) << 24 |
    (add ? 1 : 0) << 23 |
    (ldPSR ? 1 : 0) << 22 |
    (wb ? 1 : 0) << 21 |
    (load ? 1 : 0) << 20 |
    rn << 16 |
    regs.fold(0, (o, x) => o | 1 << x);
}

class SWP extends Instruction {
  SWP(CondCode cond, this.singleByte, this.rn, this.rd, this.rm) : super(cond);

  final bool singleByte;
  final int rn;
  final int rd;
  final int rm;

  assemble() =>
    cond.index << 28 |
    0x2 << 23 |
    (singleByte ? 1 : 0) << 22 |
    rn << 16 |
    rd << 12 |
    0x9 << 4 |
    rm;
}

class SWI extends Instruction {
  SWI(CondCode cond, this.data) : super(cond) {
    assert(data == data & 0xFFFFFF);
  }
  int data;
  assemble() => cond.index << 28 | 0xF << 24 | data;
}

int _parseInt(String s) {
  var np = new RegExp(r"^(0o[0-7]+|0b[0-1]+|0x[0-9A-Fa-f]+|[0-9]+)$").matchAsPrefix(s);
  if (np == null) return null;
  var pf = np.group(0).length > 2 ? np.group(0).substring(1, 2) : "";
  var str = pf == "x" || pf == "b" || pf == "o" ? np.group(0).substring(2) : np.group(0);
  return int.parse(str, radix: pf == "x" ? 16 : pf == "b" ? 2 : pf == "o" ? 8 : 10);
}

List<String> instructionNames = [
  "BX","BL", "B",
  "SWI", "SVC",
  "MRS",
  "MSR",
  "STR", "LDR",
  "STM", "LDM",
  "SWP",
  "PUSH", "POP",
]..addAll(kDPInstCodeStrings)..addAll(kMultiplyInstNames)..addAll(kMultiplyLongInstNames);

const List<String> registerNames = const [
  "r0", "r1", "r2", "r3",
  "r4", "r5", "r6", "r7",
  "r8", "sb", "r10", "r11",
  "ip", "sp", "lr", "pc",
];

class Address {
  Address(this.reg, this.offset, this.pre, this.wb, this.add);
  final int reg;
  final Offset offset;
  final bool pre;
  final bool wb;
  final bool add;
}

int _parseReg(String e) {
  e = e.toLowerCase();
  int o;
  if (e.startsWith("r")) {
    o = int.parse(e.substring(1));
  } else if (e.startsWith("a")) {
    var x = int.parse(e.substring(1));
    assert(x >= 1 && x <= 4);
    o = x - 1;
  } else if (e.startsWith("v")) {
    var x = int.parse(e.substring(1));
    assert(x >= 1 && x <= 8);
    o = x + 3;
  } else if (registerNames.contains(e)) {
    o = registerNames.indexOf(e);
  } else o = _parseInt(e);
  if (o == null || o < 0 || o > 15) return null;
  return o;
}

abstract class Instruction {
  factory Instruction.decode(String line) {
    var ss = line.split(" ");
    var rawop = ss.first.toUpperCase();
    var sargs = ss.skip(1).join(" ").split(",").map((e) => e.trim()).toList();

    int readImmediate() {
      var e = sargs.removeAt(0);
      if (!e.startsWith("#")) throw "Invalid immediate";
      var o = _parseInt(e.substring(1));
      if (o == null) throw "Invalid immediate";
      return o;
    }

    int readReg() {
      if (sargs.length == 0) throw "Register expected before eol";
      var o = _parseReg(sargs.removeAt(0));
      if (o == null) throw "Invalid register";
      return o;
    }

    Shift readShift() {
      var e = sargs.removeAt(0);
      var ss = e.split(" ");
      if (ss.length > 2 || ss.length < 1) throw "Invalid shift";
      var sn = ss[0].toUpperCase();
      if (!kShiftTypeNames.containsKey(sn)) throw "Invalid shift type";
      var st = kShiftTypeNames[sn];
      if (ss[1].startsWith("#")) {
        var sx = _parseInt(ss[1].substring(1));
        if (sx == null) throw "Invalid shift amount";
        return new Shift(st, false, sx);
      } else {
        var r = _parseReg(ss[1]);
        if (r == null) throw "Invalid shift register";
        return new Shift(st, true, r);
      }
    }

    Operand readOperand() {
      var e = sargs.first;
      if (e.startsWith("#")) {
        sargs.removeAt(0);
        var o = _parseInt(e.substring(1));
        if (o == null) throw "Invalid operand immediate";
        return new ImmediateOperand(o);
      } else {
        return new RegisterOperand(readReg(), sargs.length == 0 ? Shift.NO_OP : readShift());
      }
    }

    SourcePSR readPSR() {
      var e = sargs.removeAt(0).toUpperCase();
      if (e == "CPSR" || e == "CPSR_ALL") {
        return SourcePSR.CPSR;
      } else if (e == "SPSR" || e == "SPSR_ALL") {
        return SourcePSR.SPSR;
      } else throw "Invalid PSR";
    }

    Address readAddress([bool noShift = false]) {
      var e = sargs.first;
      if (e.startsWith("#")) {
        return new Address(15, new ImmediateOffset(readImmediate()), true, false, true);
      } else if (!e.startsWith("[") || sargs.length > 3) throw "Invalid address";
      sargs[0] = sargs[0].substring(1);

      var preIdx = sargs.length == 1;
      var wb = false;
      var l = sargs.last;
      if (l.endsWith("]!") && sargs.length > 1) {
        wb = true;
        sargs[sargs.length - 1] = l.substring(0, l.length - 2);
        preIdx = true;
      } else if (l.endsWith("]") && sargs.length > 1) {
        sargs[sargs.length - 1] = l.substring(0, l.length - 1);
        preIdx = true;
      } else {
        if (!sargs[0].endsWith("]")) throw "Invalid address";
        sargs[0] = sargs.first.substring(0, sargs.first.length - 1);
      }

      var reg = _parseReg(sargs[0]);
      if (reg == null) throw "Invalid address register";

      if (sargs.length > 1) {
        if (sargs[1].startsWith("#")) {
          var imm = _parseInt(sargs[1].substring(1));
          if (imm == null) throw "Invalid offset shift immediate";
          if (sargs.length > 2) throw "Invalid address";
          sargs = [];
          return new Address(reg, new ImmediateOffset(imm), preIdx, wb, true);
        } else {
          var inc = true;
          if (sargs[1].startsWith("+")) {
            sargs[1] = sargs[1].substring(1);
          } else if (sargs[1].startsWith("-")) {
            inc = false;
            sargs[1] = sargs[1].substring(1);
          }

          var shiftReg = _parseReg(sargs[1]);
          if (shiftReg == null) throw "Invalid offset";

          var shiftVal = 0;
          var shiftType = ShiftType.Left;

          if (sargs.length > 2) {
            if (noShift) throw "Invalid address";
            var e = sargs[2];
            var ss = e.split(" ");
            if (ss.length > 2 || ss.length < 1) throw "Invalid shift";
            var sn = ss[0].toUpperCase();
            if (!kShiftTypeNames.containsKey(sn)) throw "Invalid shift type";
            shiftType = kShiftTypeNames[sn];
            if (ss[1].startsWith("#")) {
              shiftVal = _parseInt(ss[1].substring(1));
              if (shiftVal == null) throw "Invalid shift amount";
            } else throw "Invalid shift";
          }

          sargs = [];
          return new Address(reg, new RegisterOffset(new Shift(shiftType, false, shiftVal), shiftReg), preIdx, wb, inc);
        }
      } else {
        return new Address(reg, new ImmediateOffset(0), preIdx, wb, true);
      }
    }

    List<int> readRList() {
      var e = sargs.join(",");
      sargs = [];
      if (!e.startsWith("{") || !e.endsWith("}")) throw "Invalid register list";
      e = e.substring(1, e.length - 1).replaceAll(" ", "");

      var out = new Set<int>();
      for (var rs in e.split(",")) {
        var m = new RegExp(r"^(.+)\-(.+)$").matchAsPrefix(rs);
        if (m != null) {
          var ra = _parseReg(m.group(1));
          var rb = _parseReg(m.group(2));
          if (ra > rb || ra == null || rb == null) throw "Invalid register list range";
          for (int i = ra; i <= rb; i++) out.add(i);
        } else {
          var r = _parseReg(rs);
          if (r == null) throw "Invalid register";
          out.add(r);
        }
      }

      return out.toList();
    }

    CondCode cond = CondCode.AL;
    var flags = new Set<String>();

    var op = instructionNames.firstWhere((e) => rawop.startsWith(e), orElse: () => throw "Unknown instruction");

    rawop = rawop.substring(op.length);
    for (var c in kCondCodeStrings.keys) if (rawop.contains(c)) {
      cond = CondCode.values[kCondCodeStrings[c]];
      rawop = rawop.replaceFirst(c, "");
      break;
    }

    while (rawop.length > 0) {
      pf(String name) {
        if (rawop.startsWith(name)) {
          rawop = rawop.substring(name.length);
          if (!flags.add(name)) throw "Duplicate flag";
        }
      }
      int l = rawop.length;

      if (kDPInstCodeStrings.contains(op) || kMultiplyLongInstNames.contains(op) || kMultiplyInstNames.contains(op)) {
        pf("S");
      } else if (op == "LDR" || op == "STR") {
        pf("B"); pf("T");
      } else if ((op == "LDM" || op == "STM") && flags.isEmpty) {
        pf("FD"); pf("ED"); pf("FA"); pf("EA");
        pf("IA"); pf("IB"); pf("DA"); pf("DB");
      } else if (op == "SWP") {
        pf("B");
      }

      if (rawop.length == l) throw "Unknown flags \"$rawop\"";
    }

    if (kDPInstCodeStrings.contains(op) || (kDPInstCodeStrings.contains(op.substring(0, op.length - 1)) && op.endsWith("S"))) {
      var inst = DPInstCode.values[kDPInstCodeStrings.indexOf(op)];

      if (const ["MOV", "MVN"].contains(op)) {
        var rd = readReg();
        var op2 = readOperand();
        return new DPInst(cond, inst, flags.contains("S"), 0, rd, op2);
      } else if (const ["CMP", "CMN", "TEQ", "TST"].contains(op)) {
        var rn = readReg();
        var op2 = readOperand();
        return new DPInst(cond, inst, true, rn, 0, op2);
      } else {
        var rd = readReg();
        var rn = readReg();
        var op2 = readOperand();
        return new DPInst(cond, inst, flags.contains("S"), rn, rd, op2);
      }
    } else if (op == "MUL" || op == "MLA") {
      var rd = readReg();
      var rm = readReg();
      var rs = readReg();
      var rn = op == "MUL" ? 0 : readReg();
      return new Multiply(cond, op == "MLA", flags.contains("S"), rd, rn, rs, rm);
    } else if (kMultiplyLongInstNames.contains(op)) {
      var rdLo = readReg();
      var rdHi = readReg();
      var rm = readReg();
      var rs = readReg();
      return new MultiplyLong(cond, op.startsWith("S"), op.endsWith("AL"), flags.contains("S"), rdHi, rdLo, rs, rm);
    } else if (op == "B" || op == "BL") {
      var offset = readImmediate();
      return new Branch(cond, op == "BL", offset);
    } else if (op == "BX") {
      var rn = readReg();
      return new BranchExchange(cond, rn);
    } else if (op == "SWI" || op == "SVC") {
      var comment = readImmediate();
      return new SWI(cond, comment);
    } else if (op == "MRS") {
      var rd = readReg();
      var ps = readPSR();
      return new MRS(cond, ps, rd);
    } else if (op == "MSR") {
      var pd = readPSR();
      var op2 = readOperand();
      return new MSR(cond, pd, op2);
    } else if (["STR", "LDR"].contains(op)) {
      if (["H", "SH", "SB"].any((e) => flags.contains(e))) {
        var rd = readReg();
        var addr = readAddress(true);
        var offset = addr.offset;
        var sgn = op == "LDR" && (flags.contains("SH") || flags.contains("SB"));
        var half  = op == "LDR" && (flags.contains("SH") || flags.contains("H"));
        if (offset is ImmediateOffset) {
          return new HalfwordSignedDataTransfer(cond, addr.pre, addr.add, addr.wb, op == "LDR", addr.reg, rd, sgn, half, true, offset.offset);
        } else if (offset is RegisterOffset) {
          return new HalfwordSignedDataTransfer(cond, addr.pre, addr.add, addr.wb, op == "LDR", addr.reg, rd, sgn, half, false, offset.rm);
        } else throw "Internal error";
      } else {
        var byte = flags.contains("B");
        var post = flags.contains("T");
        var rd = readReg();
        var addr = readAddress();
        return new SingleDataTransfer(cond, addr.pre, addr.add, byte, addr.wb || post, op.startsWith("LDR"), addr.reg, rd, addr.offset);
      }
    } else if (["LDM", "STM"].contains(op)) {
      bool wb = false;
      if (sargs.length > 0 && sargs.first.endsWith("!")) {
        wb = true;
        sargs[0] = sargs[0].substring(0, sargs[0].length - 1);
      }

      var sf = flags.isEmpty ? "IA" : flags.first;
      var rl = op == "LDM" ?
        const {"ED": "IB", "FD": "IA", "EA": "DB", "FA": "DA"} :
        const {"ED": "DA", "FD": "DB", "EA": "IA", "FA": "IB"};
      if (rl.containsKey(sf)) sf = rl[sf];

      var p = sf.endsWith("B");
      var u = sf.startsWith("I");

      var psr = false;
      if (sargs.length > 1 && sargs[1].endsWith("^")) {
        sargs[1] = sargs[1].substring(0, sargs[1].length - 1).trim();
        psr = true;
      }

      var rn = readReg();
      var regs = readRList();

      return new BlockDataTransfer(cond, p, u, psr, wb, op == "LDM", rn, regs);
    } else if (op == "SWP") {
      var rd = readReg();
      var rm = readReg();
      if (sargs.isEmpty || !sargs.first.startsWith("[") || !sargs.first.endsWith("]")) throw "Invalid address";
      sargs[0] = sargs[0].substring(1, sargs[0].length - 1);
      var rn = readReg();

      return new SWP(cond, flags.contains("B"), rn, rd, rm);
    }
    throw "Internal error";
  }
  Instruction(this.cond);

  final CondCode cond;

  int assemble();
  int asseleLE() {
    var x = assemble();
    return
      x >> 24 |
      (x & 0xFF0000) >> 8 |
      (x & 0xFF00) << 8 |
      (x & 0xFF) << 24;
  }
}