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Statistical sampling library for use in virtualdataset libraries, based on apache commons math 4
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/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.spi;

import ch.qos.logback.core.CoreConstants;

import java.util.List;

/**
 * This class computes caller data returning the result in the form
 * of a StackTraceElement array.
 *
 * @author Ceki Gülcü
 */
public class CallerData {

    /**
     * When caller information is not available this constant is used for file
     * name, method name, etc.
     */
    public static final String NA = "?";

    // All logger call's in log4j-over-slf4j use the Category class
    private static final String LOG4J_CATEGORY = "org.apache.log4j.Category";
    private static final String SLF4J_BOUNDARY = "org.slf4j.Logger";

    /**
     * When caller information is not available this constant is used for the line
     * number.
     */
    public static final int LINE_NA = -1;

    public static final String CALLER_DATA_NA = "?#?:?" + CoreConstants.LINE_SEPARATOR;

    /**
     * This value is returned in case no caller data could be extracted.
     */
    public static final StackTraceElement[] EMPTY_CALLER_DATA_ARRAY = new StackTraceElement[0];

    /**
     * Extract caller data information as an array based on a Throwable passed as
     * parameter
     */
    public static StackTraceElement[] extract(Throwable t, String fqnOfInvokingClass, final int maxDepth, List frameworkPackageList) {
        if (t == null) {
            return null;
        }

        StackTraceElement[] steArray = t.getStackTrace();
        StackTraceElement[] callerDataArray;

        int found = LINE_NA;
        for (int i = 0; i < steArray.length; i++) {
            if (isInFrameworkSpace(steArray[i].getClassName(), fqnOfInvokingClass, frameworkPackageList)) {
                // the caller is assumed to be the next stack frame, hence the +1.
                found = i + 1;
            } else {
                if (found != LINE_NA) {
                    break;
                }
            }
        }

        // we failed to extract caller data
        if (found == LINE_NA) {
            return EMPTY_CALLER_DATA_ARRAY;
        }

        int availableDepth = steArray.length - found;
        int desiredDepth = maxDepth < (availableDepth) ? maxDepth : availableDepth;

        callerDataArray = new StackTraceElement[desiredDepth];
        for (int i = 0; i < desiredDepth; i++) {
            callerDataArray[i] = steArray[found + i];
        }
        return callerDataArray;
    }

    static boolean isInFrameworkSpace(String currentClass, String fqnOfInvokingClass, List frameworkPackageList) {
        // the check for org.apache.log4j.Category class is intended to support
        // log4j-over-slf4j. it solves http://bugzilla.slf4j.org/show_bug.cgi?id=66
        if (currentClass.equals(fqnOfInvokingClass) || currentClass.equals(LOG4J_CATEGORY) || currentClass.startsWith(SLF4J_BOUNDARY)
                        || isInFrameworkSpaceList(currentClass, frameworkPackageList)) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * Is currentClass present in the list of packages considered part of the logging framework?
     */
    private static boolean isInFrameworkSpaceList(String currentClass, List frameworkPackageList) {
        if (frameworkPackageList == null)
            return false;

        for (String s : frameworkPackageList) {
            if (currentClass.startsWith(s))
                return true;
        }
        return false;
    }

    /**
     * Returns a StackTraceElement where all string fields are set to {@link #NA} and line number is set to {@link #LINE_NA}.
     *
     * @return StackTraceElement with values set to NA constants.
     * @since 1.0.10
     */
    public static StackTraceElement naInstance() {
        return new StackTraceElement(NA, NA, NA, LINE_NA);
    }

}