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package com.sun.jdo.api.persistence.enhancer.classfile;

import java.io.PrintStream;

/**
 * An instruction which requires a integral constant as an immediate operand 
 */

public class InsnIntOp extends Insn {
  /* The operand */
  private int operandValue;

  /* public accessors */

  public int nStackArgs() {
    return VMOp.ops[opcode()].nStackArgs();
  }

  public int nStackResults() {
    return VMOp.ops[opcode()].nStackResults();
  }

  public String argTypes() {
    return VMOp.ops[opcode()].argTypes();
  }

  public String resultTypes() {
    return VMOp.ops[opcode()].resultTypes();
  }

  public boolean branches() {
    return opcode() == opc_ret;
  }

  public int value() {
    return operandValue;
  }

  /* package local methods */

  static String primType(int primIndex) {
    switch (primIndex) {
    case T_BOOLEAN:
        return "boolean";//NOI18N
    case T_CHAR:
        return "char";//NOI18N
    case T_FLOAT:
        return "float";//NOI18N
    case T_DOUBLE:
        return "double";//NOI18N
    case T_BYTE:
        return "byte";//NOI18N
    case T_SHORT:
        return "short";//NOI18N
    case T_INT:
        return "int";//NOI18N
    case T_LONG:
        return "long";//NOI18N
    default:
        throw new InsnError ("Invalid primitive type(" + primIndex + ")");//NOI18N
    }
  }

  void print (PrintStream out, int indent) {
    ClassPrint.spaces(out, indent);
    if (opcode() == opc_newarray) 
        out.println(offset() + "  opc_newarray  " + primType(operandValue));//NOI18N
    else
        out.println(offset() + "  " + opName(opcode()) + "  " + operandValue);//NOI18N
  }

  int store(byte[] buf, int index) {
    if (size() == 4) {
      /* prefix with an opc_wide */
      buf[index++] = (byte) opc_wide;
    }

    buf[index++] = (byte) opcode();
    if (size() > 2)
      buf[index++] = (byte)(operandValue >> 8);
    buf[index++] = (byte)(operandValue & 0xff);
    return index;
  }


  /* return the size of the instruction in bytes */

  int size() {
    switch(opcode()) {
    case opc_bipush:
    case opc_newarray:
      /* These are always 1 byte constants */
      return 2;

    case opc_sipush: /* a short constant */
      /* This is always a 2 byte constant */
      return 3;

    case opc_iload:
    case opc_lload:
    case opc_fload:
    case opc_dload:
    case opc_aload:
    case opc_istore:
    case opc_lstore:
    case opc_fstore:
    case opc_dstore:
    case opc_astore:
    case opc_ret:
      /* These can be one or two byte constants specifying a local var.
       * If a two byte constant, the constant is prefixed by a wide
       * instruction */
      if (operandValue < 256)
	return 2;
      else
	return 4;

    default:
        throw new InsnError ("invalid instruction " + opName(opcode()) +//NOI18N
                             " with an integer operand");//NOI18N
    }
  }


  InsnIntOp (int theOpcode, int theOperand, int pc) {
    super(theOpcode, pc);

    operandValue = theOperand;
  }


  InsnIntOp (int theOpcode, int theOperand) {
    super(theOpcode, NO_OFFSET);

    operandValue = theOperand;
    switch(theOpcode) {
    case opc_bipush:
    case opc_newarray:
      /* These are always 1 byte constants */

    case opc_sipush: /* a short constant */
      /* This is always a 2 byte constant */

    case opc_dload:
    case opc_lload:
    case opc_iload:
    case opc_fload:
    case opc_aload:
    case opc_istore:
    case opc_lstore:
    case opc_fstore:
    case opc_dstore:
    case opc_astore:
    case opc_ret:
      /* These can be one or two byte constants specifying a local var */
      break;

    default:
        throw new InsnError ("attempt to create an " + opName(theOpcode) +//NOI18N
                             " with an integer operand");//NOI18N
    }
  }
}