macedon_cache.cc

这是一个著名的应用层组播中间件的源码

//Copyright (c) 2004, Charles Killian, Adolfo Rodriguez, Dejan Kostic, Sooraj Bhat, and Amin Vahdat
//All rights reserved.
//
//Redistribution and use in source and binary forms, with or without
//modification, are permitted provided that the following conditions are met:
//
//   * Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//   * 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.
//   * Neither the names of Duke University nor The University of
//     California, San Diego, 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 OWNER 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.

#include "macedon_cache.h"
#include "macedon.h"


mac_cache::mac_cache()
  : num_entries(0)
{
}

mac_cache::~mac_cache()
{
}

void mac_cache::consistency()
{
  for (int i=0; i<num_entries; i++) {
    if (wall_clock() > entries[i].time + MAX_CACHE_LIFE) {
#ifdef CACHE_TRACE
      printf("Cache %f: Nuking stale %.8x %.8x %.8x\n",wall_clock(),entries[i].upper_start, entries[i].upper_end, entries[i].lower);
#endif
      if (i != num_entries-1)
	entries[i] = entries[num_entries-1];
      num_entries--;
      return;
    }
  }
  return;
}

void mac_cache::insert(int upper_s, int upper_e, int lower) 
{
  consistency();
  for (int i=0; i<num_entries; i++) {
    if (entries[i].lower == lower) {
      if ( entries[i].upper_start != upper_s || entries[i].upper_end != upper_e)
#ifdef CACHE_TRACE
	printf("Cache %f: Updating %.8x %.8x %.8x\n", wall_clock(),upper_s, upper_e, lower);
#endif
      entries[i].upper_start = upper_s;
      entries[i].upper_end = upper_e;
      entries[i].time = wall_clock();
      return;
    }
  }
  if (num_entries == MAX_CACHE_SIZE) 
    throw_out_oldest();
  
#ifdef CACHE_TRACE
  printf("Cache %f: Adding %.8x %.8x %.8x\n", wall_clock(),upper_s, upper_e, lower);
#endif
  entries[num_entries].upper_start = upper_s;
  entries[num_entries].upper_end = upper_e;
  entries[num_entries].lower = lower;
  entries[num_entries].time = wall_clock();
  num_entries++;
  return;
}

void mac_cache::throw_out_oldest() 
{
  if (num_entries != MAX_CACHE_SIZE) 
    return;
  double oldest_time = entries[0].time;
  int oldest = 0;
  for (int i=1; i<num_entries; i++)
    {
      if (entries[i].time < oldest_time) {
	oldest_time = entries[i].time;
	oldest=i;
      }
    }

#ifdef CACHE_TRACE
  printf("Cache %f: Nuking oldest %.8x %.8x %.8x\n",wall_clock(), entries[oldest].upper_start, entries[oldest].upper_end, entries[oldest].lower);
#endif
  num_entries--;
  entries[oldest] = entries[num_entries];
}

void mac_cache::remove(int node) 
{
  for (int i=0; i<num_entries; i++) {
    if(entries[i].lower == node) {
      num_entries--;
      if(i < num_entries) {
        entries[i] = entries[num_entries];
      }
    }
  }
}

int mac_cache::query(int upper_query)
{
  //return 0;
  consistency();
  for (int i=0; i<num_entries; i++) {
    if (entries[i].upper_start == upper_query || 
        (entries[i].upper_start != entries[i].upper_end && 
         isinrangeright(upper_query, entries[i].upper_start, entries[i].upper_end))) {
#ifdef CACHE_TRACE
      printf("Cache: Using mapping %x (%x %x) to %x\n", upper_query, entries[i].upper_start, entries[i].upper_end, entries[i].lower);
#endif
      return entries[i].lower;
    }
  }
  return 0;
}