/* 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.Bounds;
import com.cburch.logisim.data.Direction;
import com.cburch.logisim.instance.InstanceFactory;
import com.cburch.logisim.instance.InstancePainter;
import com.cburch.logisim.instance.InstanceState;
import com.cburch.logisim.instance.Port;
import com.cburch.logisim.util.GraphicsUtil;
import com.cburch.logisim.util.StringUtil;
/** Manufactures a simple counter that iterates over the 4-bit Gray Code. This
* example illustrates how a component can maintain its own internal state. All
* of the code relevant to state, though, appears in CounterData class. */
class SimpleGrayCounter extends InstanceFactory {
private static final BitWidth BIT_WIDTH = BitWidth.create(4);
// Again, notice how we don't have any instance variables related to an
// individual instance's state. We can't put that here, because only one
// SimpleGrayCounter object is ever created, and its job is to manage all
// instances that appear in any circuits.
public SimpleGrayCounter() {
super("Gray Counter (Simple)");
setOffsetBounds(Bounds.create(-30, -15, 30, 30));
setPorts(new Port[] {
new Port(-30, 0, Port.INPUT, 1),
new Port( 0, 0, Port.OUTPUT, BIT_WIDTH.getWidth()),
});
}
@Override
public void propagate(InstanceState state) {
// Here I retrieve the state associated with this component via a helper
// method. In this case, the state is in a CounterData object, which is
// also where the helper method is defined. This helper method will end
// up creating a CounterData object if one doesn't already exist.
CounterData cur = CounterData.get(state, BIT_WIDTH);
boolean trigger = cur.updateClock(state.getPort(0));
if (trigger) cur.setValue(GrayIncrementer.nextGray(cur.getValue()));
state.setPort(1, cur.getValue(), 9);
// (You might be tempted to determine the counter's current value
// via state.getPort(1). This is erroneous, though, because another
// component may be pushing a value onto the same point, which would
// "corrupt" the value found there. We really do need to store the
// current value in the instance.)
}
@Override
public void paintInstance(InstancePainter painter) {
painter.drawBounds();
painter.drawClock(0, Direction.EAST); // draw a triangle on port 0
painter.drawPort(1); // draw port 1 as just a dot
// Display the current counter value centered within the rectangle.
// However, if the context says not to show state (as when generating
// printer output), then skip this.
if (painter.getShowState()) {
CounterData state = CounterData.get(painter, BIT_WIDTH);
Bounds bds = painter.getBounds();
GraphicsUtil.drawCenteredText(painter.getGraphics(),
StringUtil.toHexString(BIT_WIDTH.getWidth(), state.getValue().toIntValue()),
bds.getX() + bds.getWidth() / 2,
bds.getY() + bds.getHeight() / 2);
}
}
}