btcontent.cpp

最经典的bittorrent协议的实现的源码

  return retval;
}

void btContent::CacheClean(size_t need)
{
  BTCACHE *p, *pnext;
  int f_flush = 0;

  if( m_flush_failed ) FlushCache();  // try again

  again:
  for( p=m_cache_oldest; p && m_cache_size < m_cache_used + need; p=pnext ){
    pnext = p->age_next;
    if( f_flush ) FlushEntry(p);
    if( !p->bc_f_flush ){
      if( p->age_prev ) p->age_prev->age_next = p->age_next;
      else m_cache_oldest = p->age_next;
      if( p->age_next ) p->age_next->age_prev = p->age_prev;
      else m_cache_newest = p->age_prev;

      if( p->bc_prev ) p->bc_prev->bc_next = p->bc_next;
      if( p->bc_next ) p->bc_next->bc_prev = p->bc_prev;

      size_t idx = p->bc_off / m_piece_length;
      if( p->bc_next && p->bc_next->bc_off / m_piece_length == idx )
        m_cache[idx] = p->bc_next;
      else m_cache[idx] = (BTCACHE *)0;

      m_cache_used -= p->bc_len;
      delete []p->bc_buf;
      delete p;
    }
  }
  if( m_cache_size < m_cache_used + need ){  // still not enough
    if( m_cache_size < cfg_cache_size*1024*1024 ){  // can alloc more
      m_cache_size = (m_cache_used + need > cfg_cache_size*1024*1024) ?
        cfg_cache_size*1024*1024 : (m_cache_used + need);
    }
    if( m_cache_size < m_cache_used + need && m_cache_used && !f_flush ){
      if(arg_verbose) CONSOLE.Debug("CacheClean flushing to obtain space");
      f_flush = 1;
      goto again;
    }  // else we tried...
  }
}

// Don't call this function if cfg_cache_size==0 !
void btContent::CacheEval()
{
  BTCACHE *p = m_cache_oldest;
  size_t interval;
  size_t unflushed = 0, dlnext, upadd = 0, upmax = 0, upmin = 0, total;

  size_t rateup = Self.RateUL();
  size_t ratedn = Self.RateDL();
  size_t unchoked = WORLD.GetUnchoked();

  // Time until next cache size eval: unchoke interval or time to dl a piece.
  if( ratedn ){
    interval = m_piece_length / ratedn;
    if( interval > WORLD.GetUnchokeInterval() )
      interval = WORLD.GetUnchokeInterval();
    else if( 0==interval ) interval = 1;
  }else interval = WORLD.GetUnchokeInterval();

  // Download: total unflushed data + data to dl before next eval
  // Hold the first piece a bit to let uploading begin.
  if( pBF->IsFull() ) dlnext = 0;
  else{
    if( pBF->Count() < 2 ) unflushed = m_cache_used;
    else for( ; p; p = p->age_next )
      if( p->bc_f_flush ) unflushed += p->bc_len;
    // Make sure we can read back and check a completed piece.
    dlnext = ratedn * interval + m_piece_length;
    // Set a shorter interval if DL cache need is very high.
    if( ratedn ){
      size_t max =
        (cfg_cache_size*1024*1024 - unflushed - m_piece_length) / ratedn;
      if( interval > max ) interval = max;
    }
  }

  // Upload: need enough to hold read/dl'd data until it can be sent
  upmin = DEFAULT_SLICE_SIZE * unchoked;
  upmax = cfg_cache_size*1024*1024;
  if( pBF->IsFull() ){
    // Seed mode.  All cache data is prefetched, and we don't normally need to
    // keep prefetched data longer than 2.5 unchoke intervals.
    if( rateup && unchoked ){
      // A very slow peer can't possibly benefit from cache--don't grow for it.
      size_t slowest = (size_t)( 1 + DEFAULT_SLICE_SIZE /
                                 ((double)cfg_cache_size*1024*1024 / rateup) );
      // Lead cache: data we need to cache to keep the slowest up's data cached
      // Add a slice per up for timing uncertainty
      if( slowest = WORLD.GetSlowestUp(slowest) )
        upadd = DEFAULT_SLICE_SIZE * ( rateup / slowest + unchoked-1 );
      else upadd = DEFAULT_SLICE_SIZE * unchoked;

      upmin = DEFAULT_SLICE_SIZE * unchoked;
      upmax = (size_t)( DEFAULT_SLICE_SIZE * (unchoked-1) +
        rateup * 2.5 * WORLD.GetUnchokeInterval() );
    }
  }else{
    if( rateup > ratedn ){
      size_t slowest = (size_t)( 1 +
        cfg_req_slice_size * ((double)ratedn / cfg_cache_size*1024*1024) +
        DEFAULT_SLICE_SIZE * ((double)rateup / cfg_cache_size*1024*1024) );
      if( slowest = WORLD.GetSlowestUp(slowest) )
        // lead cache is how much we'll use while uploading a slice to slowest
        // (default_slice_size / slowest) * (ratedn + rateup)
        upadd = (size_t)( ((double)DEFAULT_SLICE_SIZE / slowest) *
                          (ratedn + rateup + 1) );
      else upadd = m_piece_length * unchoked;
    }
    else if( rateup ){
      // same as m_piece_length / (cfg_cache_size*1024*1024 / (double)ratedn)
      size_t slowest = (size_t)( 1 +
        ratedn * ((double)m_piece_length / (cfg_cache_size*1024*1024)) );
      if( slowest = WORLD.GetSlowestUp(slowest) ){
        // m_piece_length / (double)slowest * ratedn
        // optimize, then round up a piece and add a piece
        upadd = m_piece_length * (ratedn / slowest + 2);
      }else{  // gimme 10 seconds worth (unchoke interval)
        // Can't keep pieces in cache long enough to upload them.
        // Rely on prefetching slices from disk instead.
        upadd = ratedn * WORLD.GetUnchokeInterval() +
                DEFAULT_SLICE_SIZE * unchoked;
      }
    }
  }

  if( upadd < upmin ) upadd = upmin;

  // Add a slice to round up
  total = unflushed + dlnext + upadd + cfg_req_slice_size;

  // Limit to max configured size
  if( total > cfg_cache_size*1024*1024 ) total = cfg_cache_size*1024*1024;

  // Don't decrease cache size if flush failed.
  if( !m_flush_failed || total > m_cache_size ) m_cache_size = total;

  if(arg_verbose)
    CONSOLE.Debug("DL need: %dK  UL need: %dK  Cache: %dK  Used: %dK",
    (int)((unflushed+dlnext)/1024), (int)(upadd/1024),
    (int)(m_cache_size/1024), (int)(m_cache_used/1024));
  m_cache_eval_time = now + interval;
}

void btContent::CacheConfigure()
{
  if( cfg_cache_size ){
    if( cfg_cache_size > GetTotalFilesLength()/1024/1024 )
      cfg_cache_size = (GetTotalFilesLength()+1024*1024-1)/1024/1024;
    CacheEval();
  }else m_cache_size = 0;

  if( m_cache_size < m_cache_used && !m_flush_failed ) CacheClean(0);
}

int btContent::NeedFlush() const
{
  if( m_flush_failed ){
    if( now > m_flush_tried ) return 1;
  }else return m_flushq ? 1 : 0;
}

void btContent::FlushCache(size_t idx)
{
  BTCACHE *p, *pnext;

  if( idx >= m_npieces ){
    if(arg_verbose) CONSOLE.Debug("Flushing all cache");
    if( m_flushq) do{
      FlushQueue();
    }while( m_flushq && !m_flush_failed );
    p = m_cache_oldest;
  } else p = m_cache[idx];

  for( ; p; p = pnext ){
    pnext = (idx < m_npieces) ? p->bc_next : p->age_next;
    if( idx == p->bc_off / m_piece_length ||
        (p->bc_f_flush && idx == m_npieces) ||
        idx == (p->bc_off+p->bc_len-1) / m_piece_length ){
      // update the age--flushing the entry or its piece
      if( m_cache_newest != p ){
        if( p->age_prev ) p->age_prev->age_next = p->age_next;
        else if( p->age_next ) m_cache_oldest = p->age_next;
        if( p->age_next ) p->age_next->age_prev = p->age_prev;
        m_cache_newest->age_next = p;
        p->age_next = (BTCACHE *)0;
        p->age_prev = m_cache_newest;
        m_cache_newest = p;
      }
      if( p->bc_f_flush ) FlushEntry(p);
    }
  }
}

void btContent::FlushEntry(BTCACHE *p)
{
  if( p->bc_f_flush ){
    if( m_btfiles.IO(p->bc_buf, p->bc_off, p->bc_len, 1) < 0 ){
      m_flush_tried = now;
      if( now >= m_flush_failed + 300 ){
        if( !m_flush_failed )
          m_cache_size += cfg_req_slice_size * WORLD.GetDownloads() * 2;
        CONSOLE.Warning(1, "warn, write file failed while flushing cache.");
        CONSOLE.Warning(1,
          "You need to have at least %llu bytes free on this filesystem!",
          (unsigned long long)(m_left_bytes + m_cache_used));
        CONSOLE.Warning(1,
          "This could also be caused by a conflict or disk error.");
        if( !IsFull() ||
            (!m_flush_failed && m_cache_size > cfg_cache_size*1024*1024) ){
          CONSOLE.Warning(1, "Temporarily %s%s...",
            IsFull() ? "" : "suspending download",
            (!m_flush_failed && m_cache_size > cfg_cache_size*1024*1024) ?
              (IsFull() ? " and increasing cache" : "increasing cache") : "");
        }
        m_flush_failed = now;
        WORLD.StopDownload();
      }
    }else{
      p->bc_f_flush = 0;
      if( Seeding() ){
        for( size_t n=1; n <= m_btfiles.GetNFiles(); n++ )
          m_btfiles.CloseFile(n);  // files will reopen read-only
      }
      if(m_flush_failed){
        m_flush_failed = 0;
        CONSOLE.Warning(3, "Flushing cache succeeded%s.",
          Seeding() ? "" : "; resuming download");
        CacheConfigure();
        WORLD.CheckInterest();
      }
    }
  }
}

void btContent::Uncache(size_t idx)
{
  BTCACHE *p, *pnext;

  p = m_cache[idx];
  for( ; p; p = pnext ){
    pnext = p->bc_next;
    if( idx == p->bc_off / m_piece_length ){
      if( p->age_prev ) p->age_prev->age_next = p->age_next;
      else m_cache_oldest = p->age_next;
      if( p->age_next ) p->age_next->age_prev = p->age_prev;
      else m_cache_newest = p->age_prev;

      if( p->bc_prev ) p->bc_prev->bc_next = p->bc_next;
      if( p->bc_next ) p->bc_next->bc_prev = p->bc_prev;

      m_cache_used -= p->bc_len;
      delete []p->bc_buf;
      delete p;
    }else break;
  }
  m_cache[idx] = (BTCACHE *)0;
}

void btContent::FlushQueue()
{
  if( !m_flushq ) return;

  if(arg_verbose)
    CONSOLE.Debug("Writing piece #%d to disk", (int)(m_flushq->idx));
  FlushCache(m_flushq->idx);
  if( !m_flush_failed ){
    BTFLUSH *goner = m_flushq;
    m_flushq = m_flushq->next;
    delete goner;
  }
}

ssize_t btContent::WriteSlice(char *buf,size_t idx,size_t off,size_t len)
{
  uint64_t offset = (uint64_t)idx * (uint64_t)m_piece_length + off;

  //CONSOLE.Debug("Offset-write: %llu - Piece:%lu",
  //  (unsigned long long)offset, (unsigned long)idx);

  if( !m_cache_size ) return m_btfiles.IO(buf, offset, len, 1);
  else{
    size_t len2;
    int flg_rescan;
    BTCACHE *p;

    p = m_cache[idx];
    for( ; p && (offset + len) > p->bc_off && !CACHE_FIT(p,offset,len);
        p = p->bc_next );

    for( ; len && p && CACHE_FIT(p, offset, len); ){
      flg_rescan = 0;
      if( offset < p->bc_off ){
        len2 = p->bc_off - offset;
        if( CacheIO(buf, offset, len2, 1) < 0 ) return -1;
        flg_rescan = 1;
      }else{
        if( offset > p->bc_off ){
          len2 = p->bc_off + p->bc_len - offset;
          if( len2 > len ) len2 = len;
          memcpy(p->bc_buf + offset - p->bc_off, buf, len2);
          p->bc_f_flush = 1;
        }else{
          len2 = (len > p->bc_len) ? p->bc_len : len;
          memcpy(p->bc_buf, buf, len2);
          p->bc_f_flush = 1;
        }
        // re-received this data, make it new again
        if( m_cache_newest != p ){
          if( p->age_prev ) p->age_prev->age_next = p->age_next;
          else if( p->age_next ) m_cache_oldest = p->age_next;
          if( p->age_next ) p->age_next->age_prev = p->age_prev;
          m_cache_newest->age_next = p;
          p->age_next = (BTCACHE *)0;
          p->age_prev = m_cache_newest;
          m_cache_newest = p;
        }
      }

      buf += len2;
      offset += len2;
      len -= len2;

      if( len ){
        if( flg_rescan ){
          for( p = m_cache[idx];
               p && (offset + len) > p->bc_off && !CACHE_FIT(p,offset,len);
               p = p->bc_next );
        }else{
          p = p->bc_next;
        }
      }
    }// end for;
  
    if( len ) return CacheIO(buf, offset, len, 1);
  }
  return 0;
}

ssize_t btContent::CacheIO(char *buf, uint64_t off, size_t len, int method)
{
  BTCACHE *p;
  BTCACHE *pp = (BTCACHE*) 0;
  BTCACHE *pnew = (BTCACHE*) 0;

  if(arg_verbose && 0==method)
    CONSOLE.Debug("Read to %s %d/%d/%d", buf?"buffer":"cache",
      (int)(off / m_piece_length), (int)(off % m_piece_length), (int)len);

  if( m_cache_size < m_cache_used + len ) CacheClean(len);
  // Note, there is no failure code from CacheClean().  If nothing can be done
  // to increase the cache size, we allocate what we need anyway.
  
  if( 0==method && buf && m_btfiles.IO(buf, off, len, method) < 0 ) return -1;
  
  pnew = new BTCACHE;
#ifndef WINDOWS
  if( !pnew )
    return (method && buf) ? m_btfiles.IO(buf, off, len, method) : 0;
#endif

  pnew->bc_buf = new char[len];
#ifndef WINDOWS
  if( !(pnew->bc_buf) ){ 
    delete pnew; 
    return (method && buf) ? m_btfiles.IO(buf, off, len, method) : 0;
  }
#endif

  if( buf ) memcpy(pnew->bc_buf, buf, len);
  else if( 0==method && m_btfiles.IO(pnew->bc_buf, off, len, method) < 0 )
    return -1;
  pnew->bc_off = off;
  pnew->bc_len = len;
  pnew->bc_f_flush = method;
  m_cache_used += len;
  pnew->age_next = (BTCACHE *)0;
  if( m_cache_newest ){
    pnew->age_prev = m_cache_newest;
    m_cache_newest->age_next = pnew;
  }else{
    pnew->age_prev = (BTCACHE *)0;
    m_cache_oldest = pnew;
  }
  m_cache_newest = pnew;

  // find insert point: after pp, before p.
  size_t idx = off / m_piece_length;
  p = m_cache[idx];
  if( p ) pp = p->bc_prev;
  for( ; p && off > p->bc_off; pp = p, p = pp->bc_next );

  pnew->bc_next = p;
  pnew->bc_prev = pp;
  if( pp ) pp->bc_next = pnew;
  if( p ) p->bc_prev = pnew;
  if( !m_cache[idx] || off < m_cache[idx]->bc_off )
    m_cache[idx] = pnew;

  return 0;
}

ssize_t btContent::ReadPiece(char *buf,size_t idx)
{
  return ReadSlice(buf, idx, 0, GetPieceLength(idx));
}

size_t btContent::GetPieceLength(size_t idx)
{
  return (idx == m_btfiles.GetTotalLength() / m_piece_length) ?
    (size_t)(m_btfiles.GetTotalLength() % m_piece_length) 
    :m_piece_length;
}

int btContent::CheckExist()
{
  size_t idx = 0;
  size_t percent = GetNPieces() / 100;
  unsigned char md[20];

  if( !percent ) percent = 1;

  CONSOLE.Interact_n("");
  for( ; idx < m_npieces; idx++ ){
    if( GetHashValue(idx, md) < 0 ){
      CONSOLE.Warning(1, "Error while checking piece %d of %d",
        (int)idx+1, (int)m_npieces);
      return -1;
    }
    if( memcmp(md, m_hash_table + idx * 20, 20) == 0 ){
       m_left_bytes -= GetPieceLength(idx);
       pBF->Set(idx);
    }
    if( idx % percent == 0 || idx == m_npieces-1 )
      CONSOLE.InteractU("Check exist: %d/%d", idx+1, m_npieces);
  }
  m_check_piece = m_npieces;
  pBChecked->SetAll();
  delete pBRefer;
  return 0;
}

int btContent::CheckNextPiece()
{
  size_t idx = m_check_piece;
  unsigned char md[20];
  int f_checkint = 0;

  if( idx >= m_npieces ) return 0;
  if( !pBRefer->IsSet(idx) ){
    while( idx < m_npieces && !pBRefer->IsSet(idx) ){
      pBChecked->Set(idx);
      ++idx;
    }
    f_checkint = 1;
    m_check_piece = idx;
  }