X-Git-Url: https://mograsim.net/gitweb/?a=blobdiff_plain;f=era.mi%2Fsrc%2Fera%2Fmi%2Flogic%2FBit.java;h=11184439127c887dc8fe655359739d7f1400e2ba;hb=f2cd90fa2b844507bc9697d3af1f3e18aac80b37;hp=b18c5974f9d576442eb2e13256654fbf23dc8f1b;hpb=5f74819aeebd1f133d3513bc2db9f2258a76c4ad;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..11184439 100644
--- a/era.mi/src/era/mi/logic/Bit.java
+++ b/era.mi/src/era/mi/logic/Bit.java
@@ -1,62 +1,108 @@
-package era.mi.logic;
-
-
-public enum Bit
-{
-	ONE, ZERO, Z, X;
-	
-	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 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 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 not()
-	{
-		switch(this)
-		{
-		case ONE:
-			return Bit.ZERO;
-		case ZERO:
-			return Bit.ONE;
-		default:
-			return Bit.X;
-		}
-	}
-}
+package era.mi.logic;
+
+import java.util.Arrays;
+
+/**
+ * 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)
+	{
+		return fromTable(AND_TABLE, this, other);
+	}
+
+	public static Bit or(Bit a, Bit b)
+	{
+		return a.or(b);
+	}
+
+	public Bit or(Bit other)
+	{
+		return fromTable(OR_TABLE, this, other);
+	}
+
+	public static Bit xor(Bit a, Bit b)
+	{
+		return a.xor(b);
+	}
+
+	public Bit xor(Bit other)
+	{
+		return fromTable(XOR_TABLE, this, other);
+	}
+
+	public Bit not()
+	{
+		switch (this)
+		{
+		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;
+	}
+
+	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 final 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 final 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 final 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 final 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