toxcore/core/ping.c

/*
 * ping.c -- Buffered pinging using cyclic arrays.
 *
 * This file is donated to the Tox Project.
 * Copyright 2013  plutooo
 */

#include <stdbool.h>
#include <stdint.h>

#include "network.h"
#include "util.h"

#define PING_NUM_MAX 256
#define PING_TIMEOUT 5 // 5s

typedef struct {
  IP_Port  ipp;
  uint64_t id;
  uint64_t timestamp;
} pinged_t;

static pinged_t pings[PING_NUM_MAX];
static size_t   num_pings;
static size_t   pos_pings;


void init_ping() {
  num_pings = 0;
  pos_pings = 0;
}

static bool is_timeout(uint64_t time) {
  return (time + PING_TIMEOUT) < now();
}

static void remove_timeouts() { // O(n)
  size_t i, id;
  size_t new_pos = pos_pings;
  size_t new_num = num_pings;

  // Loop through buffer, oldest first
  for(i=0; i<num_pings; i++) {
    id = (pos_pings + i) % PING_NUM_MAX;

    if(is_timeout(pings[id].timestamp)) {
      new_pos++;
      new_num--;
    }
    // Break here because list is sorted.
    else
      break;
  }

  num_pings = new_num;
  pos_pings = new_pos % PING_NUM_MAX;
}

uint64_t add_ping(IP_Port ipp) { // O(n)
  size_t p;
  
  remove_timeouts();

  // Remove oldest ping if full buffer
  if(num_pings == PING_NUM_MAX) {
    num_pings--;
    pos_pings = (pos_pings + 1) % PING_NUM_MAX;
  }

  // Insert new ping at end of list
  p = (pos_pings + num_pings) % PING_NUM_MAX;

  pings[p].ipp       = ipp;
  pings[p].timestamp = now();
  pings[p].id        = random_64b();

  num_pings++;
  return pings[p].id;
}

bool is_pinging(IP_Port ipp, uint64_t ping_id) { // O(n)
  size_t i, id;

  remove_timeouts();

  for(i=0; i<num_pings; i++) {
    id = (pos_pings + i) % PING_NUM_MAX;

    if(ipp_eq(pings[id].ipp, ipp) && pings[id].id == ping_id) {
      return true;
    }
  }

  return false;
}