Optimized switch creation by detecting more simple switches.

src/main/java/de/neemann/digital/core/ObservableValue.java

@@ -16,6 +16,7 @@ public class ObservableValue extends Observable implements PinDescription {
     private long value;
     private boolean highZ;
     private boolean bidirectional;
+    private boolean isConstant = false;
     private String description;
 
     /**
@@ -47,43 +48,52 @@ public class ObservableValue extends Observable implements PinDescription {
         supportsHighZ = highZ;
     }
 
+
     /**
-     * Sets the value and fires a event if value has changed.
+     * Makes this value a constant value
+     */
+    public void setConstant() {
+        isConstant = true;
+    }
+
+    /**
+     * @return true if this value is a constant
+     */
+    public boolean isConstant() {
+        return isConstant;
+    }
+
+    /**
+     * Sets the value and fires an event if value has changed.
+     * Also sets this value to low Z
      *
      * @param value the new value
      * @return this for chained calls
      */
     public ObservableValue setValue(long value) {
-        value = getValueBits(value);
+        set(value, false);
-        if (this.value != value) {
-            this.value = value;
-            if (!highZ)
-                fireHasChanged();
-        }
         return this;
     }
 
     /**
-     * Sets the highZ state of this value
+     * Sets the value and highZ state and fires an event if value has changed.
-     *
-     * @param highZ the new highZ state
-     */
-    public void setHighZ(boolean highZ) {
-        if (this.highZ != highZ) {
-            this.highZ = highZ;
-            fireHasChanged();
-        }
-    }
-
-    /**
-     * Sets the value and highZ state
      *
      * @param value the value
      * @param highZ highZ state
+     * @return this for chained calls
      */
-    public void set(long value, boolean highZ) {
+    public ObservableValue set(long value, boolean highZ) {
-        setValue(value);
+        value = getValueBits(value);
-        setHighZ(highZ);
+        if (highZ != this.highZ || (!highZ && (value != this.value))) {
+
+            if (isConstant)
+                throw new RuntimeException("tried to modify a constant value!");
+
+            this.highZ = highZ;
+            this.value = value;
+            fireHasChanged();
+        }
+        return this;
     }
 
     /**
@@ -243,21 +253,13 @@ public class ObservableValue extends Observable implements PinDescription {
     /**
      * Makes this value a bidirectional value.
      *
-     * @param bidirectional true if value is bidirectional
      * @return this for chained calls
      */
-    public ObservableValue setBidirectional(boolean bidirectional) {
+    public ObservableValue setBidirectional() {
-        this.bidirectional = bidirectional;
+        this.bidirectional = true;
         return this;
     }
 
-    /**
-     * @return true if value is bidirectional
-     */
-    public boolean isBidirectional() {
-        return bidirectional;
-    }
-
     @Override
     public String getDescription() {
         if (description != null)

src/main/java/de/neemann/digital/core/io/Const.java

@@ -35,6 +35,7 @@ public class Const implements Element {
     public Const(ElementAttributes attributes) {
         output = new ObservableValue("out", attributes.get(Keys.BITS)).setPinDescription(DESCRIPTION);
         output.setValue(attributes.get(Keys.VALUE));
+        output.setConstant();
     }
 
     @Override

src/main/java/de/neemann/digital/core/io/Ground.java

@@ -34,6 +34,7 @@ public class Ground implements Element {
     public Ground(ElementAttributes attributes) {
         output = new ObservableValue("out", attributes.get(Keys.BITS)).setPinDescription(DESCRIPTION);
         output.setValue(0);
+        output.setConstant();
     }
 
     @Override

src/main/java/de/neemann/digital/core/io/VDD.java

@@ -34,6 +34,7 @@ public class VDD implements Element {
     public VDD(ElementAttributes attributes) {
         output = new ObservableValue("out", attributes.get(Keys.BITS)).setPinDescription(DESCRIPTION);
         output.setValue(-1);
+        output.setConstant();
     }
 
     @Override

src/main/java/de/neemann/digital/core/memory/RAMDualPort.java

@@ -158,7 +158,7 @@ public class RAMDualPort extends Node implements Element, RAMInterface {
         if (ld) {
             output.set(memory.getDataWord(addr), false);
         } else {
-            output.setHighZ(true);
+            output.set(0, true);
         }
     }
 

src/main/java/de/neemann/digital/core/memory/RAMSinglePort.java

@@ -48,7 +48,7 @@ public class RAMSinglePort extends RAMDualPort {
     @Override
     protected ObservableValue createOutput() {
         return super.createOutput()
-                .setBidirectional(true)
+                .setBidirectional()
                 .setPinDescription(DESCRIPTION);
     }
 

src/main/java/de/neemann/digital/core/memory/RAMSinglePortSel.java

@@ -62,7 +62,7 @@ public class RAMSinglePortSel extends Node implements Element, RAMInterface {
         size = 1 << addrBits;
         memory = new DataField(size);
         label = attr.getCleanLabel();
-        dataOut = new ObservableValue("D", bits, true).setPinDescription(DESCRIPTION).setBidirectional(true);
+        dataOut = new ObservableValue("D", bits, true).setPinDescription(DESCRIPTION).setBidirectional();
     }
 
     @Override
@@ -92,7 +92,7 @@ public class RAMSinglePortSel extends Node implements Element, RAMInterface {
         if (cs && oe) {
             dataOut.set(memory.getDataWord(addr), false);
         } else {
-            dataOut.setHighZ(true);
+            dataOut.set(0, true);
         }
     }
 

src/main/java/de/neemann/digital/core/pld/Diode.java

@@ -31,8 +31,8 @@ public class Diode implements Element, Observer {
      * @param attr the elements attributes
      */
     public Diode(ElementAttributes attr) {
-        cathode = new ObservableValue("cathode", 1, true).setBidirectional(true);
+        cathode = new ObservableValue("cathode", 1, true).setBidirectional();
-        anode = new ObservableValue("anode", 1, true).setBidirectional(true);
+        anode = new ObservableValue("anode", 1, true).setBidirectional();
         blown = attr.get(Keys.BLOWN);
     }
 

src/main/java/de/neemann/digital/core/switching/Switch.java

@@ -47,10 +47,8 @@ public class Switch implements Element, Observer {
     public Switch(ElementAttributes attr, boolean closed) {
         bits = attr.getBits();
         this.closed = closed;
-        output1 = new ObservableValue("out1", bits, true).setPinDescription(DESCRIPTION).setBidirectional(true);
+        output1 = new ObservableValue("out1", bits, true).setPinDescription(DESCRIPTION).setBidirectional().set(0, true);
-        output2 = new ObservableValue("out2", bits, true).setPinDescription(DESCRIPTION).setBidirectional(true);
+        output2 = new ObservableValue("out2", bits, true).setPinDescription(DESCRIPTION).setBidirectional().set(0, true);
-        output1.set(0, true);
-        output2.set(0, true);
     }
 
     @Override
@@ -59,7 +57,18 @@ public class Switch implements Element, Observer {
         ObservableValue input2 = inputs.get(1).addObserverToValue(this).checkBits(bits, null);
         if (input1 instanceof CommonBusValue) {
             if (input2 instanceof CommonBusValue) {
-                switchModel = new RealSwitch((CommonBusValue) input1, (CommonBusValue) input2);
+                final CommonBusValue in1 = (CommonBusValue) input1;
+                final CommonBusValue in2 = (CommonBusValue) input2;
+                ObservableValue constant = in1.searchConstant();
+                if (constant != null)
+                    switchModel = new SimpleSwitch(constant, output2);
+                else {
+                    constant = in2.searchConstant();
+                    if (constant != null)
+                        switchModel = new SimpleSwitch(constant, output1);
+                    else
+                        switchModel = new RealSwitch(in1, in2);
+                }
             } else {
                 switchModel = new SimpleSwitch(input1, output2);
             }
@@ -116,14 +125,14 @@ public class Switch implements Element, Observer {
     /**
      * @return output 1
      */
-    public ObservableValue getOutput1() {
+    ObservableValue getOutput1() {
         return output1;
     }
 
     /**
      * @return output 2
      */
-    public ObservableValue getOutput2() {
+    ObservableValue getOutput2() {
         return output2;
     }
 

src/main/java/de/neemann/digital/core/wiring/bus/CommonBusValue.java

@@ -30,14 +30,14 @@ public final class CommonBusValue extends ObservableValue implements Observer {
      *
      * @param handler the handler
      */
-    public void setHandler(AbstractBusHandler handler) {
+    void setHandler(AbstractBusHandler handler) {
         this.handler = handler;
     }
 
     /**
-     * Resets the handler. SO this net is isolated to a single simple net.
+     * Resets the handler. So this net is isolated to a single simple net.
      */
-    public void resetHandler() {
+    void resetHandler() {
         setHandler(new SingleBusHandler(obs, this, resistor, inputs));
         hasChanged();
     }
@@ -55,4 +55,16 @@ public final class CommonBusValue extends ObservableValue implements Observer {
     public ObservableValue[] getInputs() {
         return inputs;
     }
+
+    /**
+     * Returns true if this net is a constant
+     *
+     * @return true if this is a constant
+     */
+    public ObservableValue searchConstant() {
+        for (ObservableValue i : inputs)
+            if (i.isConstant())
+                return i;
+        return null;
+    }
 }

src/main/java/de/neemann/digital/gui/components/SingleValueDialog.java

@@ -218,7 +218,7 @@ public final class SingleValueDialog extends JDialog {
         SingleValueDialog svd = new SingleValueDialog(pos, value);
         if (svd.showDialog()) {
             if (svd.getSelectedFormat().equals(InMode.HIGHZ)) {
-                modelSync.access(() -> value.setHighZ(true));
+                modelSync.access(() -> value.set(0, true));
             } else {
                 modelSync.access(() -> value.set(svd.editValue, false));
             }

src/main/java/de/neemann/digital/gui/components/graphics/GraphicCard.java

@@ -80,7 +80,7 @@ public class GraphicCard extends Node implements Element, RAMInterface {
 
         dataOut = new ObservableValue("D", bits, true)
                 .setPinDescription(DESCRIPTION)
-                .setBidirectional(true);
+                .setBidirectional();
     }
 
     @Override
@@ -135,7 +135,7 @@ public class GraphicCard extends Node implements Element, RAMInterface {
         if (ld) {
             dataOut.set(memory.getDataWord(addr), false);
         } else {
-            dataOut.setHighZ(true);
+            dataOut.set(0, true);
         }
     }