X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=src%2Fnet%2Fsf%2Fopenrocket%2Flogging%2FTraceException.java;fp=src%2Fnet%2Fsf%2Fopenrocket%2Flogging%2FTraceException.java;h=55397641f177dddc1e457b363a93c33a50b2ed13;hb=e298a9509613f232227d16d28310611b33c3aa03;hp=0000000000000000000000000000000000000000;hpb=c71eeba85a8a25e1bd43b27ad09cb2238139b737;p=debian%2Fopenrocket

diff --git a/src/net/sf/openrocket/logging/TraceException.java b/src/net/sf/openrocket/logging/TraceException.java
new file mode 100644
index 00000000..55397641
--- /dev/null
+++ b/src/net/sf/openrocket/logging/TraceException.java
@@ -0,0 +1,113 @@
+package net.sf.openrocket.logging;
+
+
+
+/**
+ * An exception that is used to store a stack trace.  On modern computers
+ * instantiation of an exception takes on the order of one microsecond, while
+ * examining the trace typically takes longer.  Therefore the exception should
+ * be stored and the stack trace examined only when necessary.
+ * <p>
+ * The {@link #getMessage()} method returns a description of the position
+ * where this exception has been instantiated.  The position is provided
+ * as many levels upwards from the instantiation position as provided to the
+ * constructor.
+ * 
+ * @author Sampo Niskanen <sampo.niskanen@iki.fi>
+ */
+public class TraceException extends Exception {
+	
+	private static final String STANDARD_PACKAGE_PREFIX = "net.sf.openrocket.";
+
+	private final int minLevel;
+	private final int maxLevel;
+	private String message = null;
+	
+	
+	/**
+	 * Instantiate exception that provides the line of instantiation as a message.
+	 */
+	public TraceException() {
+		this(0, 0);
+	}
+	
+	/**
+	 * Instantiate exception that provides the provided number of levels upward
+	 * from the instantiation location as a message.  The level provided 
+	 * is how many levels upward should be examined to find the stack trace 
+	 * position for the exception message.
+	 * 
+	 * @param level		how many levels upward to examine the stack trace to find
+	 * 					the correct message.
+	 */
+	public TraceException(int level) {
+		this(level, level);
+	}
+	
+	
+	/**
+	 * Instantiate exception that provides a range of levels upward from the
+	 * instantiation location as a message.  This is useful to identify the
+	 * next level of callers upward.
+	 * 
+	 * @param minLevel	the first level which to include.
+	 * @param maxLevel	the last level which to include.
+	 */
+	public TraceException(int minLevel, int maxLevel) {
+		if (minLevel > maxLevel || minLevel < 0) {
+			throw new IllegalArgumentException("minLevel="+minLevel+" maxLevel="+maxLevel);
+		}
+		this.minLevel = minLevel;
+		this.maxLevel = maxLevel;
+	}
+
+
+	/**
+	 * Get the description of the code position as provided in the constructor.
+	 */
+	@Override
+	public String getMessage() {
+		if (message == null) {
+			StackTraceElement[] elements = this.getStackTrace();
+
+			StringBuilder sb = new StringBuilder();
+			if (minLevel < elements.length) {
+				
+				sb.append("(");
+				sb.append(toString(elements[minLevel]));
+				for (int i=minLevel+1; i <= maxLevel; i++) {
+					if (i < elements.length) {
+						sb.append(' ').append(toString(elements[i]));
+					}
+				}
+				sb.append(')');
+				
+			} else if (elements.length == 0) {
+				
+				sb.append("(no stack trace)");
+				
+			} else {
+
+				sb.append('(');
+				sb.append(toString(elements[0]));
+				for (int i=1; i < elements.length; i++) {
+					sb.append(' ').append(toString(elements[i]));
+				}
+				sb.append(" level=").append(minLevel).append(')');
+				
+			}
+			message = sb.toString();
+		}
+		return message;
+	}
+	
+	
+	private static String toString(StackTraceElement element) {
+		if (element.getClassName().startsWith(STANDARD_PACKAGE_PREFIX)) {
+			return element.getFileName() + ":" + element.getLineNumber();
+		} else {
+			return element.toString();
+		}
+	}
+	
+}