ReaderException.cs

/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
namespace com.google.zxing
{
	
	/// <summary> The general exception class throw when something goes wrong during decoding of a barcode.
	/// This includes, but is not limited to, failing checksums / error correction algorithms, being
	/// unable to locate finder timing patterns, and so on.
	/// 
	/// </summary>
	/// <author>  Sean Owen
	/// </author>
	/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
	/// </author>

	[Serializable]
	public sealed class ReaderException:System.Exception
	{
		public static ReaderException Instance
		{
			get
			{
				//    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;
			}
			
		}
		
		// 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.
		
		//UPGRADE_NOTE: Final was removed from the declaration of 'instance '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		private static readonly 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 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.
		//UPGRADE_NOTE: Exception 'java.lang.Throwable' was converted to 'System.Exception' which has different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1100'"
		//UPGRADE_NOTE: The equivalent of method 'java.lang.Throwable.fillInStackTrace' is not an override method. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1143'"
		public System.Exception fillInStackTrace()
		{
			return null;
		}
	}
}