added sources for Slick

Former-commit-id: 1647fa32ef6894bd7db44f741f07c2f4dcdf9054
Former-commit-id: 0e5810dcfbe1fd59b13e7cabe9f1e93c5542da2d

lib/slick-source/org/newdawn/slick/util/FastTrig.java

@@ -0,0 +1,56 @@
+package org.newdawn.slick.util;
+
+/**
+ * Utility to handle Java's odd trig performance issues
+ *
+ * @author JeffK
+ */
+public class FastTrig {
+   /**
+	 * Fast Trig functions for x86.  
+	 * This forces the trig functiosn to stay within the safe area on the x86 processor (-45 degrees to +45 degrees)
+	 * The results may be very slightly off from what the Math and StrictMath trig functions give due to
+	 * rounding in the angle reduction but it will be very very close.
+	 * 
+	 * @param radians The original angle
+	 * @return The reduced Sin angle
+	 */
+	private static double reduceSinAngle(double radians) {
+		double orig = radians;
+		radians %= Math.PI * 2.0; // put us in -2PI to +2PI space
+		if (Math.abs(radians) > Math.PI) { // put us in -PI to +PI space
+			radians = radians - (Math.PI * 2.0);
+		}
+		if (Math.abs(radians) > Math.PI / 2) {// put us in -PI/2 to +PI/2 space
+			radians = Math.PI - radians;
+		}
+
+		return radians;
+	}
+
+	/**
+	 * Get the sine of an angle
+	 * 
+	 * @param radians The angle
+	 * @return The sine of the angle
+	 */
+	public static double sin(double radians) {
+		radians = reduceSinAngle(radians); // limits angle to between -PI/2 and +PI/2
+		if (Math.abs(radians) <= Math.PI / 4) {
+			return Math.sin(radians);
+		} else {
+			return Math.cos(Math.PI / 2 - radians);
+		}
+	}
+
+	/**
+	 * Get the cosine of an angle
+	 * 
+	 * @param radians The angle
+	 * @return The cosine of the angle
+	 */
+	public static double cos(double radians) {
+		return sin(radians + Math.PI / 2);
+	}
+
+}