text: /*
   * ppbloom.c - Ping-Pong Bloom Filter for nonce reuse detection
   *
   * Copyright (C) 2013 - 2018, Max Lv <max.c.lv@gmail.com>
   *
   * This file is part of the shadowsocks-libev.
   *
   * shadowsocks-libev is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 3 of the License, or
   * (at your option) any later version.
   *
   * shadowsocks-libev is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with shadowsocks-libev; see the file COPYING. If not, see
   * <http://www.gnu.org/licenses/>.
   */
  
  #include <errno.h>
  #include <stdlib.h>
  
  #include "bloom.h"
  #include "ppbloom.h"
  #include "utils.h"
  
  #define PING 0
  #define PONG 1
  
  static struct bloom ppbloom[2];
  static int bloom_count[2];
  static int current;
  static int entries;
  static double error;
  
  int
  ppbloom_init(int n, double e)
  {
      int err;
      entries = n / 2;
      error   = e;
  
      err = bloom_init(ppbloom + PING, entries, error);
      if (err)
          return err;
  
      err = bloom_init(ppbloom + PONG, entries, error);
      if (err)
          return err;
  
      bloom_count[PING] = 0;
      bloom_count[PONG] = 0;
  
      current = PING;
  
      return 0;
  }
  
  int
  ppbloom_check(const void *buffer, int len)
  {
      int ret;
  
      ret = bloom_check(ppbloom + PING, buffer, len);
      if (ret)
          return ret;
  
      ret = bloom_check(ppbloom + PONG, buffer, len);
      if (ret)
          return ret;
  
      return 0;
  }
  
  int
  ppbloom_add(const void *buffer, int len)
  {
      int err;
      err = bloom_add(ppbloom + current, buffer, len);
      if (err == -1)
          return err;
  
      bloom_count[current]++;
  
      if (bloom_count[current] >= entries) {
          bloom_count[current] = 0;
          current              = current == PING ? PONG : PING;
          bloom_free(ppbloom + current);
          bloom_init(ppbloom + current, entries, error);
      }
  
      return 0;
  }
  
  void
  ppbloom_free()
  {
      bloom_free(ppbloom + PING);
      bloom_free(ppbloom + PONG);
  }
  