Improve performance of string comparison.

src/core/org/luaj/vm2/LuaString.java

@@ -261,22 +261,28 @@ public class LuaString extends LuaValue {
 	// object comparison, used in key comparison
 	public boolean equals( Object o ) {
 		if ( o instanceof LuaString ) {
-			LuaString s = (LuaString) o;
+			return eq_b( (LuaString) o );
+		}
+		return false;
+	}
+
+	public boolean eq_b( LuaString s ) { 
+		if ( s == this )
+			return true;
 		if ( s.m_length != m_length )
 			return false;
+		if ( s.m_bytes == m_bytes && s.m_offset == m_offset )
+			return true;
 		if ( s.hashCode() != hashCode() )
 			return false;
 		for ( int i=0; i<m_length; i++ )
 			if ( s.m_bytes[s.m_offset+i] != m_bytes[m_offset+i] )
 				return false;
 		return true;
-		} else {
-			return false;
-		}
 	}
 	
 	public boolean eq_b( LuaValue val ) {
-		return equals( val );
+		return val.eq_b( this );
 	}
 	
 	public static boolean equals( LuaString a, int i, LuaString b, int j, int n ) {

src/core/org/luaj/vm2/LuaValue.java

@@ -229,6 +229,7 @@ public class LuaValue extends Varargs {
 	// arithmetic equality
 	public LuaValue   eq( LuaValue val )         { return valueOf(eq_b(val)); }
 	public boolean eq_b( LuaValue val )       { return this == val; }
+	public boolean eq_b( LuaString val )       { return this == val; }
 	public boolean eq_b( double val )      { return false; }
 	public boolean eq_b( int val )         { return false; }
 	public LuaValue   neq( LuaValue val )        { return valueOf(!eq_b(val)); }