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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you 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.
 */
package org.jboss.netty.util.internal;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.util.DebugUtil;
import org.jboss.netty.util.ThreadRenamingRunnable;

/**
 * Simplifies an exception stack trace by removing unnecessary
 * {@link StackTraceElement}s.  Please note that the stack trace simplification
 * is disabled if {@linkplain DebugUtil debug mode} is turned on.
 */
public final class StackTraceSimplifier {

    private static final boolean SIMPLIFY_STACK_TRACE = !DebugUtil.isDebugEnabled();
    private static final Pattern EXCLUDED_STACK_TRACE =
        Pattern.compile(
                "^org\\.jboss\\.netty\\." +
                "(util\\.(ThreadRenamingRunnable|internal\\.DeadLockProofWorker)" +
                "|channel\\.(SimpleChannel(Upstream|Downstream)?Handler|(Default|Static)ChannelPipeline.*))(\\$.*)?$");

    /**
     * Removes unnecessary {@link StackTraceElement}s from the specified
     * exception. {@link ThreadRenamingRunnable}, {@link SimpleChannelHandler},
     * and {@link ChannelPipeline} implementations will be dropped from the
     * trace.
     */
    public static void simplify(Throwable e) {
        if (!SIMPLIFY_STACK_TRACE) {
            return;
        }

        if (e.getCause() != null) {
            simplify(e.getCause());
        }

        StackTraceElement[] trace = e.getStackTrace();
        if (trace == null || trace.length == 0) {
            return;
        }

        // Perhaps Netty bug.  Let us not strip things out.
        if (EXCLUDED_STACK_TRACE.matcher(trace[0].getClassName()).matches()) {
            return;
        }

        List simpleTrace =
            new ArrayList(trace.length);

        simpleTrace.add(trace[0]);

        // Remove unnecessary stack trace elements.
        for (int i = 1; i < trace.length; i ++) {
            if (EXCLUDED_STACK_TRACE.matcher(trace[i].getClassName()).matches()) {
                continue;
            }
            simpleTrace.add(trace[i]);
        }

        e.setStackTrace(
                simpleTrace.toArray(new StackTraceElement[simpleTrace.size()]));
    }

    private StackTraceSimplifier() {
        // Unused
    }
}