X-Git-Url: https://mograsim.net/gitweb/?a=blobdiff_plain;f=era.mi%2Fsrc%2Fera%2Fmi%2Flogic%2FBit.java;h=8010ca760b852ad3cf99f4018f48a93549c233e2;hb=de79184d60c80d6775b368e61d3368de032952e8;hp=b18c5974f9d576442eb2e13256654fbf23dc8f1b;hpb=a4c5cfb856026771dfcf31eb22434b8b6ff20ad4;p=Mograsim.git

diff --git a/era.mi/src/era/mi/logic/Bit.java b/era.mi/src/era/mi/logic/Bit.java
index b18c5974..8010ca76 100644
--- a/era.mi/src/era/mi/logic/Bit.java
+++ b/era.mi/src/era/mi/logic/Bit.java
@@ -1,62 +1,95 @@
 package era.mi.logic;
 
+import java.util.Arrays;
 
-public enum Bit
-{
-	ONE, ZERO, Z, X;
-	
-	public static Bit and(Bit a, Bit b)
-	{
+/**
+ * stdlogic according to IEEE 1164
+ */
+public enum Bit {
+	U, X, ZERO, ONE, Z;
+
+	public static Bit and(Bit a, Bit b) {
 		return a.and(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;
+
+	public Bit and(Bit other) {
+		return fromTable(AND_TABLE, this, other);
 	}
-	
-	public static Bit or(Bit a, Bit b)
-	{
+
+	public static Bit or(Bit a, Bit b) {
 		return a.or(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;
+
+	public Bit or(Bit other) {
+		return fromTable(OR_TABLE, this, other);
 	}
-	
-	public static Bit xor(Bit a, Bit b)
-	{
+
+	public static Bit xor(Bit a, Bit b) {
 		return a.xor(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;
+
+	public Bit xor(Bit other) {
+		return fromTable(XOR_TABLE, this, other);
 	}
-	
-	public Bit not()
-	{
-		switch(this)
-		{
+
+	public Bit not() {
+		switch (this) {
+		case U:
+			return U;
 		case ONE:
-			return Bit.ZERO;
+			return ZERO;
 		case ZERO:
-			return Bit.ONE;
+			return ONE;
 		default:
-			return Bit.X;
+			return X;
 		}
 	}
-}
+
+	public Bit[] makeArray(int length) {
+		Bit[] bits = new Bit[length];
+		Arrays.fill(bits, this);
+		return bits;
+	}
+
+	public Bit combineWith(Bit other) {
+		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