dmolony-DiskBrowser/src/com/bytezone/diskbrowser/infocom/Instruction.java

package com.bytezone.diskbrowser.infocom;

import java.util.ArrayList;
import java.util.List;

import com.bytezone.diskbrowser.utilities.HexFormatter;

class Instruction
{
  static int version = 3;

  final Opcode opcode;
  final int startPtr;
  private byte[] buffer;
  //	List<ZString> abbreviations;
  private Header header;

  enum OperandType
  {
    VAR_SP, VAR_LOCAL, VAR_GLOBAL, BYTE, WORD, ARG_BRANCH, ARG_STRING, OBJECT
  }

  static final String[] name2OP =
      { "*bad*", "je", "jl", "jg", "dec_chk", "inc_chk", "jin", "test", "or", "and",
        "test_attr", "set_attr", "clear_attr", "store", "insert_obj", "loadw", "loadb",
        "get_prop", "get_prop_addr", "get_next_prop", "add", "sub", "mul", "div", "mod",
        "call_2s", "call_2n", "set_colour", "throw", "*bad*", "*bad*", "*bad*" };
  static final String[] name1OP =
      { "jz", "get_sibling", "get_child", "get_parent", "get_prop_len", "inc", "dec",
        "print_addr", "call_ls", "remove_obj", "print_obj", "ret", "jump", "print_paddr",
        "load", "not" };
  static final String[] name0OP =
      { "rtrue", "rfalse", "print", "print_ret", "nop", "save", "restore", "restart",
        "ret_popped", "pop", "quit", "new_line", "show_status", "verify", "", "piracy" };
  static final String[] nameVAR =
      { "call", "storew", "storeb", "put_prop", "sread", "print_char", "print_num",
        "random", "push", "pull", "split_window", "set_window", "call_vs2",
        "erase_window", "erase_line", "set_cursor", "get_cursor", "set_text_style",
        "buffer_mode", "output_stream", "input_stream", "sound_effect", "read_char",
        "scan_table", "not", "call_vn", "call_vn2", "tokenise", "encode_text",
        "copy_table", "print_table", "check_arg" };

  Instruction (byte[] buffer, int ptr, Header header)
  {
    this.buffer = buffer;
    this.startPtr = ptr;
    this.header = header;
    byte b1 = buffer[ptr];

    int type = (b1 & 0xC0) >>> 6;
    switch (type)
    {
      case 0x03:                                      // 11 - variable
        if ((b1 & 0x20) == 0x20)
          opcode = new OpcodeVar (buffer, ptr);
        else
          opcode = new Opcode2OPVar (buffer, ptr);
        break;

      case 0x02:                                      // 10 - extended or short
        if (b1 == 0xBE && version >= 5)
          opcode = null;
        else if ((b1 & 0x30) == 0x30)
          opcode = new Opcode0OP (buffer, ptr);
        else
          opcode = new Opcode1OP (buffer, ptr);
        break;

      default:                                        // 00, 01 - long
        opcode = new Opcode2OPLong (buffer, ptr);
    }
  }

  int length ()
  {
    return opcode.length ();
  }

  boolean isReturn ()
  {
    return opcode.isReturn;
  }

  boolean isPrint ()
  {
    return opcode.string != null;
  }

  boolean isCall ()
  {
    return opcode.isCall;
  }

  boolean isJump ()
  {
    // could use jumpTarget != 0
    return (opcode instanceof Opcode1OP && opcode.opcodeNumber == 12);
  }

  boolean isBranch ()
  {
    return opcode.branch != null;
  }

  boolean isStore ()
  {
    return opcode.store != null;
  }

  int target ()
  {
    return isBranch () ? opcode.branch.target : isJump () ? opcode.jumpTarget : 0;
  }

  String dump ()
  {
    return String.format ("%05X : %s", startPtr,
        HexFormatter.getHexString (buffer, startPtr, opcode.length ()));
  }

  String getHex ()
  {
    int max = opcode.length ();
    String extra = "";
    if (max > 9)
    {
      max = 9;
      extra = "..";
    }

    String hex = HexFormatter.getHexString (buffer, startPtr, max);
    return String.format ("%05X : %-26s%2s", startPtr, hex, extra);
  }

  @Override
  public String toString ()
  {
    return opcode.toString ();
  }

  abstract class Opcode
  {
    int opcodeNumber;
    int opcodeLength;
    List<Operand> operands = new ArrayList<> ();
    int totalOperandLength;
    ArgumentBranch branch;
    ArgumentString string;
    OperandVariable store;
    boolean isReturn, isCall, isExit;
    int jumpTarget;
    int callTarget;

    @Override
    public String toString ()
    {
      StringBuilder text = new StringBuilder ();

      text.append (String.format ("%-12s", opcodeName ()));

      if (jumpTarget != 0)
        text.append (String.format (" L:%05X", jumpTarget));
      else if (isCall)
      {
        text.append (String.format (" R:%05X (", callTarget));
        int count = 0;
        for (Operand op : operands)
          if (count++ > 0)
            text.append (op + ", ");
        if (operands.size () > 1)
          text.delete (text.length () - 2, text.length ());
        text.append (") -> " + store);
      }
      else
      {
        for (Operand op : operands)
          text.append (" " + op);
        if (branch != null)
          text.append (branch);
        if (store != null)
          text.append (" -> " + store);
        if (string != null)
          text.append (" \"" + string + "\"");
      }
      return text.toString ();
    }

    int length ()
    {
      int length = totalOperandLength + opcodeLength;
      if (branch != null)
        length += branch.length;
      if (store != null)
        length += store.length;
      if (string != null)
        length += string.length;
      return length;
    }

    abstract String opcodeName ();

    private void addOperand (Operand operand)
    {
      operands.add (operand);
      totalOperandLength += operand.length;
    }

    void addOperand (byte[] buffer, int ptr, boolean bit1, boolean bit2)
    {
      int offset = ptr + totalOperandLength;
      if (bit1)
      {
        if (!bit2)
          addOperand (new OperandVariable (buffer[offset]));      // %10
      }
      else if (bit2)
        addOperand (new OperandByte (buffer[offset]));            // %01
      else
        addOperand (new OperandWord (header.getWord (offset)));   // %00
    }

    void addOperand (byte[] buffer, int ptr, boolean bit)
    {
      int address = ptr + totalOperandLength;
      if (address >= buffer.length)
      {
        System.out.println ("Illegal byte address : " + address);
        return;
      }
      if (bit)
        addOperand (new OperandVariable (buffer[address]));
      else
        addOperand (new OperandByte (buffer[address]));
    }

    void setVariableOperands (int ptr)
    {
      int value = buffer[ptr + 1] & 0xFF;
      for (int i = 0; i < 4; i++)
      {
        boolean bit1 = ((value & 0x80) == 0x80);
        boolean bit2 = ((value & 0x40) == 0x40);
        if (bit1 && bit2)
          break;
        addOperand (buffer, ptr + 2, bit1, bit2);
        value <<= 2;
      }
    }

    void setStore (byte[] buffer)
    {
      store = new OperandVariable (buffer[startPtr + totalOperandLength + opcodeLength]);
    }

    void setBranch (byte[] buffer)
    {
      int offset = startPtr + totalOperandLength + (store == null ? 0 : 1) + opcodeLength;
      if ((buffer[offset] & 0x40) != 0)
        branch = new ArgumentBranch (buffer[offset], offset);
      else
        branch = new ArgumentBranch (header.getWord (offset), offset);
    }

    void setZString (byte[] buffer)
    {
      int offset = startPtr + totalOperandLength + opcodeLength;
      string = new ArgumentString (buffer, offset);
    }
  }

  class Opcode0OP extends Opcode
  {
    Opcode0OP (byte[] buffer, int ptr)
    {
      opcodeNumber = buffer[ptr] & 0x0F;
      opcodeLength = 1;

      if (opcodeNumber == 5 || opcodeNumber == 6 || opcodeNumber == 13)
        setBranch (buffer);

      if (opcodeNumber == 0 || opcodeNumber == 1 || opcodeNumber == 3
          || opcodeNumber == 8)
        isReturn = true;

      if (opcodeNumber == 2 || opcodeNumber == 3)
        setZString (buffer);

      if (opcodeNumber == 7 || opcodeNumber == 10)
        isExit = true;
    }

    @Override
    public String opcodeName ()
    {
      return name0OP[opcodeNumber];
    }
  }

  class Opcode1OP extends Opcode
  {
    Opcode1OP (byte[] buffer, int ptr)
    {
      opcodeNumber = buffer[ptr] & 0x0F;
      opcodeLength = 1;

      boolean bit1 = ((buffer[ptr] & 0x20) == 0x20);
      boolean bit2 = ((buffer[ptr] & 0x10) == 0x10);
      addOperand (buffer, ptr + 1, bit1, bit2);

      if ((opcodeNumber >= 1 && opcodeNumber <= 4) || opcodeNumber == 8
          || opcodeNumber == 14 || opcodeNumber == 15)
        setStore (buffer);
      if (opcodeNumber <= 2)
        setBranch (buffer);
      if (opcodeNumber == 12)
        jumpTarget = (short) operands.get (0).value + startPtr - 2 + length ();
      if (opcodeNumber == 11)
        isReturn = true;
    }

    @Override
    public String opcodeName ()
    {
      return name1OP[opcodeNumber];
    }
  }

  abstract class Opcode2OP extends Opcode
  {
    Opcode2OP ()
    {
      opcodeLength = 1;
    }

    void setArguments (byte[] buffer)
    {
      if ((opcodeNumber >= 1 && opcodeNumber <= 7) || opcodeNumber == 10)
        setBranch (buffer);
      else if ((opcodeNumber >= 15 && opcodeNumber <= 25) || opcodeNumber == 8
          || opcodeNumber == 9)
        setStore (buffer);
    }

    @Override
    public String opcodeName ()
    {
      return name2OP[opcodeNumber];
    }
  }

  class Opcode2OPLong extends Opcode2OP
  {
    Opcode2OPLong (byte[] buffer, int ptr)
    {
      opcodeNumber = buffer[ptr] & 0x1F;
      boolean bit1 = ((buffer[ptr] & 0x40) == 0x40);
      boolean bit2 = ((buffer[ptr] & 0x20) == 0x20);

      if (opcodeNumber == 0x0D)                   // store (variable) value
      {
        addOperand (buffer, ptr + 1, true);       // always a variable
        addOperand (buffer, ptr + 1, bit2);
      }
      else
      {
        addOperand (buffer, ptr + 1, bit1);
        addOperand (buffer, ptr + 1, bit2);
      }

      setArguments (buffer);
    }
  }

  class Opcode2OPVar extends Opcode2OP
  {
    Opcode2OPVar (byte[] buffer, int ptr)
    {
      opcodeNumber = buffer[ptr] & 0x1F;
      opcodeLength = 2;
      setVariableOperands (ptr);
      setArguments (buffer);
    }
  }

  class OpcodeVar extends Opcode
  {
    OpcodeVar (byte[] buffer, int ptr)
    {
      opcodeNumber = buffer[ptr] & 0x1F;
      opcodeLength = 2;
      setVariableOperands (ptr);

      if (opcodeNumber == 0 || opcodeNumber == 7)
        setStore (buffer);

      if (opcodeNumber == 0)        // call routine
      {
        isCall = true;
        callTarget = operands.get (0).value * 2;
      }

      if (opcodeNumber == 3)        // put prop object propertyValue
      {
        // first parameter is the object id
        operands.get (0).operandType = OperandType.OBJECT;
      }
    }

    @Override
    public String opcodeName ()
    {
      return nameVAR[opcodeNumber];
    }
  }

  abstract class Operand
  {
    int length;
    int value;
    OperandType operandType;

    @Override
    public String toString ()
    {
      switch (operandType)
      {
        case VAR_SP:
          return ("(SP)");

        case VAR_LOCAL:
          return (String.format ("L%02X", value - 1));

        case VAR_GLOBAL:
          return String.format ("G%02X", (value - 16));

        case BYTE:
          return String.format ("#%02X", value);

        case WORD:
          return String.format ("#%04X", value);

        case OBJECT:
          return "\"" + header.objectManager.getObject (value - 1).getName () + "\"";

        default:
          return "*** Illegal ***";
      }
    }
  }

  class OperandWord extends Operand
  {
    OperandWord (int value)
    {
      this.value = value;
      length = 2;
      operandType = OperandType.WORD;
    }
  }

  class OperandByte extends Operand
  {
    OperandByte (byte value)
    {
      this.value = value & 0xFF;
      length = 1;
      operandType = OperandType.BYTE;
    }
  }

  class OperandVariable extends Operand
  {
    OperandVariable (byte value)
    {
      this.value = value & 0xFF;
      length = 1;

      if (this.value == 0)
        operandType = OperandType.VAR_SP;
      else if (this.value <= 15)
        operandType = OperandType.VAR_LOCAL;
      else
        operandType = OperandType.VAR_GLOBAL;
    }
  }

  class ArgumentBranch extends Operand
  {
    private int target;
    private boolean branchOnTrue;

    ArgumentBranch (byte value, int offset)
    {
      branchOnTrue = (value & 0x80) != 0;
      int val = value & 0x3F;                           // 0 - 63
      if (val <= 1)
        target = val;
      else
        target = val + offset - 1;
      length = 1;
      operandType = OperandType.ARG_BRANCH;
    }

    ArgumentBranch (int value, int offset)
    {
      branchOnTrue = (value & 0x8000) != 0;
      int val = ((value & 0x3FFF) << 18) >> 18;         // signed 14-bit number

      target = val + offset;
      length = 2;
      operandType = OperandType.ARG_BRANCH;
    }

    @Override
    public String toString ()
    {
      StringBuilder text = new StringBuilder ();
      text.append (" [" + (branchOnTrue ? "true" : "false") + "] ");
      if (target == 0 || target == 1)
        text.append (target == 0 ? "RFALSE" : "RTRUE");
      else
        text.append (String.format ("%05X", target));
      return text.toString ();
    }
  }

  class ArgumentString extends Operand
  {
    private ZString text;
    private int startPtr;
    private byte[] buffer;

    ArgumentString (byte[] buffer, int offset)
    {
      this.buffer = buffer;
      text = new ZString (header, offset);
      length = text.length;
      operandType = OperandType.ARG_STRING;
    }

    @Override
    public String toString ()
    {
      return text.value;
    }
  }
}