/* Copyright (c) 2010, Carl Burch. License information is located in the
* com.cburch.logisim.Main source code and at www.cburch.com/logisim/. */
package com.cburch.gray;
import com.cburch.logisim.data.BitWidth;
import com.cburch.logisim.data.Value;
import com.cburch.logisim.instance.InstanceData;
import com.cburch.logisim.instance.InstanceState;
/** Represents the state of a counter. */
class CounterData implements InstanceData, Cloneable {
/** Retrieves the state associated with this counter in the circuit state,
* generating the state if necessary.
*/
public static CounterData get(InstanceState state, BitWidth width) {
CounterData ret = (CounterData) state.getData();
if (ret == null) {
// If it doesn't yet exist, then we'll set it up with our default
// values and put it into the circuit state so it can be retrieved
// in future propagations.
ret = new CounterData(null, Value.createKnown(width, 0));
state.setData(ret);
} else if (!ret.value.getBitWidth().equals(width)) {
ret.value = ret.value.extendWidth(width.getWidth(), Value.FALSE);
}
return ret;
}
/** The last clock input value observed. */
private Value lastClock;
/** The current value emitted by the counter. */
private Value value;
/** Constructs a state with the given values. */
public CounterData(Value lastClock, Value value) {
this.lastClock = lastClock;
this.value = value;
}
/** Returns a copy of this object. */
@Override
public Object clone() {
// We can just use what super.clone() returns: The only instance variables are
// Value objects, which are immutable, so we don't care that both the copy
// and the copied refer to the same Value objects. If we had mutable instance
// variables, then of course we would need to clone them.
try { return super.clone(); }
catch (CloneNotSupportedException e) { return null; }
}
/** Updates the last clock observed, returning true if triggered. */
public boolean updateClock(Value value) {
Value old = lastClock;
lastClock = value;
return old == Value.FALSE && value == Value.TRUE;
}
/** Returns the current value emitted by the counter. */
public Value getValue() {
return value;
}
/** Updates the current value emitted by the counter. */
public void setValue(Value value) {
this.value = value;
}
}