text: // throttle.js
  /*
   *  Copyright (c) 2016-2018 James Leigh, Some Rights Reserved
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions are met:
   *
   *  1. Redistributions of source code must retain the above copyright notice,
   *  this list of conditions and the following disclaimer.
   *
   *  2. Redistributions in binary form must reproduce the above copyright
   *  notice, this list of conditions and the following disclaimer in the
   *  documentation and/or other materials provided with the distribution.
   *
   *  3. Neither the name of the copyright holder nor the names of its
   *  contributors may be used to endorse or promote products derived from this
   *  software without specific prior written permission.
   *
   *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   *  POSSIBILITY OF SUCH DAMAGE.
   */
  'use strict';
  
  process.setMaxListeners(process.getMaxListeners()+1);
  
  /**
   * Limits the number of concurrent processing calls to limit
   */
  module.exports = function(fn, limit) {
      const max = limit || 1;
      let currently = 0;
      const queue = [];
      const next = function(){
          if (currently < max && queue.length) {
              currently++;
              queue.shift().call();
          }
      };
      return function(/* arguments */) {
          const context = this;
          const args = arguments;
          return new Promise(function(callback, abort){
              queue.push(() => {
                  const idx = pending.indexOf(abort);
                  if (idx < 0) return next();
                  pending.splice(idx, 1);
                  callback();
              });
              pending.push(abort);
              next();
          }).then(function(){
              return fn.apply(context, args);
          }).then(function(result){
              currently--;
              next();
              return result;
          }, function(error){
              currently--;
              next();
              return Promise.reject(error);
          });
      };
  };
  
  const pending = [];
  process.on('SIGINT', () => {
      const err = Error('SIGINT');
      pending.splice(0).forEach(task => {
          task(Promise.reject(err));
      });
  }).on('SIGTERM', () => {
      const err = Error('SIGTERM');
      pending.splice(0).forEach(task => {
          task(Promise.reject(err));
      });
  });
  