preset component framework

[debian/openrocket] / src / net / sf / openrocket / motor / MotorDigest.java

diff --git a/src/net/sf/openrocket/motor/MotorDigest.java b/src/net/sf/openrocket/motor/MotorDigest.java
index e7fb9f5fd7b31261ff7bc90d6cece110b25f3388..cec3cbdc6082a37c7a43354815d7afa5effa9e12 100644 (file)
--- a/src/net/sf/openrocket/motor/MotorDigest.java
+++ b/src/net/sf/openrocket/motor/MotorDigest.java
@@ -7,6 +7,17 @@ import java.security.NoSuchAlgorithmException;
 import net.sf.openrocket.util.Coordinate;
 import net.sf.openrocket.util.TextUtil;
 
+/**
+ * A class that generated a "digest" of a motor.  A digest is a string value that
+ * uniquely identifies a motor (like a hash code or checksum).  Two motors that have
+ * the same digest behave similarly with a very high probability.  The digest can
+ * therefore be used to identify motors that otherwise have the same specifications.
+ * <p>
+ * The digest only uses a limited amount of precision, so that rounding errors won't
+ * cause differing digest results.
+ * 
+ * @author Sampo Niskanen <sampo.niskanen@iki.fi>
+ */
 public class MotorDigest {
        
        private static final double EPSILON = 0.00000000001;
@@ -24,22 +35,25 @@ public class MotorDigest {
                CG_PER_TIME(4, 1000),
                /** Thrust force per time (in mN) */
                FORCE_PER_TIME(5, 1000);
-
+               
                private final int order;
                private final int multiplier;
+               
                DataType(int order, int multiplier) {
                        this.order = order;
                        this.multiplier = multiplier;
                }
+               
                public int getOrder() {
                        return order;
                }
+               
                public int getMultiplier() {
                        return multiplier;
                }
        }
        
-
+       
        private final MessageDigest digest;
        private boolean used = false;
        private int lastOrder = -1;
@@ -54,11 +68,11 @@ public class MotorDigest {
        }
        
        
-       public void update(DataType type, int ... values) {
-
+       public void update(DataType type, int... values) {
+               
                // Check for correct order
                if (lastOrder >= type.getOrder()) {
-                       throw new IllegalArgumentException("Called with type="+type+" order="+type.getOrder()+
+                       throw new IllegalArgumentException("Called with type=" + type + " order=" + type.getOrder() +
                                        " while lastOrder=" + lastOrder);
                }
                lastOrder = type.getOrder();
@@ -70,17 +84,17 @@ public class MotorDigest {
                digest.update(bytes(values.length));
                
                // Digest the values
-               for (int v: values) {
+               for (int v : values) {
                        digest.update(bytes(v));
                }
                
        }
        
        
-       private void update(DataType type, int multiplier, double ... values) {
-
+       private void update(DataType type, int multiplier, double... values) {
+               
                int[] intValues = new int[values.length];
-               for (int i=0; i<values.length; i++) {
+               for (int i = 0; i < values.length; i++) {
                        double v = values[i];
                        v = next(v);
                        v *= multiplier;
@@ -90,7 +104,7 @@ public class MotorDigest {
                update(type, intValues);
        }
        
-       public void update(DataType type, double ... values) {
+       public void update(DataType type, double... values) {
                update(type, type.getMultiplier(), values);
        }
        
@@ -107,16 +121,15 @@ public class MotorDigest {
                byte[] result = digest.digest();
                return TextUtil.hexString(result);
        }
-
        
        
+
        private byte[] bytes(int value) {
                return new byte[] {
-                               (byte) ((value>>>24) & 0xFF), (byte) ((value>>>16) & 0xFF),
-                               (byte) ((value>>>8) & 0xFF), (byte) (value & 0xFF) 
-               };
+                               (byte) ((value >>> 24) & 0xFF), (byte) ((value >>> 16) & 0xFF),
+                               (byte) ((value >>> 8) & 0xFF), (byte) (value & 0xFF) };
        }
-
+       
        
        /**
         * Digest the contents of a thrust curve motor.  The result is a string uniquely
@@ -126,7 +139,7 @@ public class MotorDigest {
         * @return              the digest
         */
        public static String digestMotor(ThrustCurveMotor m) {
-
+               
                // Create the motor digest from data available in RASP files
                MotorDigest motorDigest = new MotorDigest();
                motorDigest.update(DataType.TIME_ARRAY, m.getTimePoints());
@@ -134,7 +147,7 @@ public class MotorDigest {
                Coordinate[] cg = m.getCGPoints();
                double[] cgx = new double[cg.length];
                double[] mass = new double[cg.length];
-               for (int i=0; i<cg.length; i++) {
+               for (int i = 0; i < cg.length; i++) {
                        cgx[i] = cg[i].x;
                        mass[i] = cg[i].weight;
                }
@@ -161,7 +174,7 @@ public class MotorDigest {
                } catch (UnsupportedEncodingException e) {
                        throw new IllegalStateException("UTF-8 encoding not supported by JRE", e);
                }
-
+               
                return TextUtil.hexString(digest.digest());
        }