Added the ability to track who is throwing exceptions and how often in the core libra...

[zxing.git] / core / src / com / google / zxing / ReaderException.java

diff --git a/core/src/com/google/zxing/ReaderException.java b/core/src/com/google/zxing/ReaderException.java
index 34dc739..4e6a90f 100644 (file)
--- a/core/src/com/google/zxing/ReaderException.java
+++ b/core/src/com/google/zxing/ReaderException.java
@@ -21,12 +21,78 @@ package com.google.zxing;
  * This includes, but is not limited to, failing checksums / error correction algorithms, being
  * unable to locate finder timing patterns, and so on.
  *
- * @author srowen@google.com (Sean Owen)
+ * @author Sean Owen
  */
 public final class ReaderException extends Exception {
 
-  public ReaderException(String message) {
-    super(message);
+  // 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.
+
+  private static final ReaderException instance = new ReaderException();
+
+  // EXCEPTION TRACKING SUPPORT
+  // Identifies who is throwing exceptions and how often. To use:
+  //
+  // 1. Uncomment these lines and the code below which uses them.
+  // 2. Uncomment the two corresponding lines in j2se/CommandLineRunner.decode()
+  // 3. Change core to build as Java 1.5 temporarily
+//  private static int exceptionCount = 0;
+//  private static Map<String,Integer> throwers = new HashMap<String,Integer>(32);
+
+  private ReaderException() {
+    // do nothing
+  }
+
+  public static ReaderException getInstance() {
+//    Exception e = new Exception();
+//    // Take the stack frame before this one.
+//    StackTraceElement stack = e.getStackTrace()[1];
+//    String key = stack.getClassName() + "." + stack.getMethodName() + "(), line " +
+//        stack.getLineNumber();
+//    if (throwers.containsKey(key)) {
+//      Integer value = throwers.get(key);
+//      value++;
+//      throwers.put(key, value);
+//    } else {
+//      throwers.put(key, 1);
+//    }
+//    exceptionCount++;
+
+    return instance;
+  }
+
+//  public static int getExceptionCountAndReset() {
+//    int temp = exceptionCount;
+//    exceptionCount = 0;
+//    return temp;
+//  }
+//
+//  public static String getThrowersAndReset() {
+//    StringBuilder builder = new StringBuilder(1024);
+//    Object[] keys = throwers.keySet().toArray();
+//    for (int x = 0; x < keys.length; x++) {
+//      String key = (String) keys[x];
+//      Integer value = throwers.get(key);
+//      builder.append(key);
+//      builder.append(": ");
+//      builder.append(value);
+//      builder.append("\n");
+//    }
+//    throwers.clear();
+//    return builder.toString();
+//  }
+
+  // Prevent stack traces from being taken
+  // srowen says: huh, my IDE is saying this is not an override. native methods can't be overridden?
+  // This, at least, does not hurt. Because we use a singleton pattern here, it doesn't matter anyhow.
+  public Throwable fillInStackTrace() {
+    return null;
   }
 
 }