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    1   /**
    2    * Copyright (c) 2004-2011 QOS.ch
    3    * All rights reserved.
    4    *
    5    * Permission is hereby granted, free  of charge, to any person obtaining
    6    * a  copy  of this  software  and  associated  documentation files  (the
    7    * "Software"), to  deal in  the Software without  restriction, including
    8    * without limitation  the rights to  use, copy, modify,  merge, publish,
    9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
    10   * permit persons to whom the Software  is furnished to do so, subject to
    11   * the following conditions:
    12   *
    13   * The  above  copyright  notice  and  this permission  notice  shall  be
    14   * included in all copies or substantial portions of the Software.
    15   *
    16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
    17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
    18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
    19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
    20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
    22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    23   *
    24   */
    25  package org.slf4j;
    26
    27  import org.slf4j.MDC;
    28
    29  public class NDC {
    30      public final static String PREFIX = "NDC";
    31
    32      private static int size() {
    33          int i = 0;
    34          while (true) {
    35              String val = MDC.get(PREFIX + i);
    36              if (val != null) {
    37                  i++;
    38              } else {
    39                  break;
    40              }
    41          }
    42          return i;
    43      }
    44
    45      public static void push(String val) {
    46          int next = size();
    47          MDC.put(PREFIX + next, val);
    48      }
    49
    50      public static String pop() {
    51          int next = size();
    52          if (next == 0) {
    53              return "";
    54          }
    55          int last = next - 1;
    56          String key = PREFIX + last;
    57          String val = MDC.get(key);
    58          MDC.remove(key);
    59          return val;
    60      }
    61
    62  }