Made some temporary changes to make throwing ReaderExceptions more efficient. Long term, we need to delete this class and change the decoders to return errors instead of throwing.

git-svn-id: https://zxing.googlecode.com/svn/trunk@669 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/ReaderException.java

@@ -23,10 +23,24 @@ package com.google.zxing;
  *
  * @author srowen@google.com (Sean Owen)
  */
-public final class ReaderException extends Exception {
+
+// TODO: Currently we throw up to 400 ReaderExceptions while scanning a single 240x240 image before
+// rejecting it. This involves a lot of overhead and memory allocation, and affects both performance
+// and latency on continuous scan clients. In the future, we should change all the decoders not to
+// throw exceptions for routine events, like not finding a barcode on a given row. Instead, we
+// should return error codes back to the callers, and simply delete this class. In the mean time, I
+// have altered this class to be as lightweight as possible, by ignoring the exception string, and
+// by disabling the generation of stack traces, which is especially time consuming. These are just
+// temporary measures, pending the big cleanup.
+public final class ReaderException extends java.lang.Throwable {
 
   public ReaderException(String message) {
-    super(message);
+    // Do not pass message to Throwable, let it get optimized out
+  }
+
+  // Prevent stack traces from being taken
+  public Throwable fillInStackTrace() {
+    return null;
   }
 
 }