package era.mi.logic;
+import java.util.Arrays;
+
+/**
+ * stdlogic according to IEEE 1164
+ */
public enum Bit
{
- ONE, ZERO, Z, X;
+ U, X, ZERO, ONE, Z;
public static Bit and(Bit a, Bit b)
{
public Bit and(Bit other)
{
- if (equals(Bit.ZERO) || other.equals(Bit.ZERO))
- return Bit.ZERO;
- else if (equals(other) && equals(Bit.ONE))
- return Bit.ONE;
- else
- return Bit.X;
+ return fromTable(AND_TABLE, this, other);
}
public static Bit or(Bit a, Bit b)
public Bit or(Bit other)
{
- if (equals(Bit.ONE) || other.equals(Bit.ONE))
- return Bit.ONE;
- else if (equals(other) && equals(Bit.ZERO))
- return Bit.ZERO;
- else
- return Bit.X;
+ return fromTable(OR_TABLE, this, other);
}
public static Bit xor(Bit a, Bit b)
public Bit xor(Bit other)
{
- // I'm uncertain how this should behave for cases where one value is neither 1 nor 0.
- // TODO: Implement xor
- return Bit.X;
+ return fromTable(XOR_TABLE, this, other);
}
public Bit not()
{
switch (this)
- {
- case ONE:
- return Bit.ZERO;
- case ZERO:
- return Bit.ONE;
- default:
- return Bit.X;
- }
+ {
+ case U:
+ return U;
+ case ONE:
+ return ZERO;
+ case ZERO:
+ return ONE;
+ default:
+ return X;
+ }
+ }
+
+ public Bit[] makeArray(int length)
+ {
+ Bit[] bits = new Bit[length];
+ Arrays.fill(bits, this);
+ return bits;
}
- /**
- * Rules for two bits that get directly connected<br>
- * <code><table>
- * <tbody>
- * <tr><td><td>X<td>0<td>1<td>Z</tr>
- * <tr><td>X<td>X<td>X<td>X<td>X</tr>
- * <tr><td>0<td>X<td>0<td>X<td>0</tr>
- * <tr><td>1<td>X<td>X<td>1<td>1</tr>
- * <tr><td>Z<td>X<td>0<td>1<td>Z</tr>
- * </tbody>
- * </table><code>
- *
- * @return the result according to the table
- *
- * @author Christian Femers
- */
public Bit combineWith(Bit other)
{
- if (this == other)
- return this;
- if (this == X || other == X)
- return X;
- if (other == Z)
- return this;
- if (this == Z)
- return other;
- return X;
+ return fromTable(JOIN_TABLE, this, other);
}
public static Bit combine(Bit a, Bit b)
{
return a.combineWith(b);
}
-}
+
+ private static Bit fromTable(Bit[][] table, Bit a, Bit b)
+ {
+ return table[a.ordinal()][b.ordinal()];
+ }
+
+ // @formatter:off
+ private static Bit[][] JOIN_TABLE =
+ { { U, U, U, U, U },
+ { U, X, X, X, X },
+ { U, X, ZERO, X, ZERO },
+ { U, X, X, ONE, ONE },
+ { U, X, ZERO, ONE, Z } };
+
+ private static Bit[][] AND_TABLE =
+ { { U, U, ZERO, U, U },
+ { U, X, ZERO, X, X },
+ { ZERO, ZERO, ZERO, ZERO, ZERO },
+ { U, X, ZERO, ONE, X },
+ { U, X, ZERO, X, X } };
+
+ private static Bit[][] OR_TABLE =
+ { { U, U, U, ONE, U },
+ { U, X, X, ONE, X },
+ { U, X, ZERO, ONE, X },
+ { ONE, ONE, ONE, ONE, ONE },
+ { U, X, X, ONE, X } };
+
+ private static Bit[][] XOR_TABLE =
+ { { U, U, U, U, U },
+ { U, X, X, X, X },
+ { U, X, ZERO, ONE, X },
+ { U, X, ONE, ZERO, X },
+ { U, X, X, X, X } };
+ // @formatter:on
+}
\ No newline at end of file