opentracker/ot_sync.c

/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
   It is considered beerware. Prost. Skol. Cheers or whatever.

   $id$ */

/* System */
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/uio.h>

/* Libowfat */
#include "byte.h"
#include "io.h"
#include "scan.h"

/* Opentracker */
#include "ot_iovec.h"
#include "ot_mutex.h"
#include "ot_stats.h"
#include "ot_sync.h"
#include "trackerlogic.h"

#ifdef WANT_SYNC_BATCH

#define OT_SYNC_CHUNK_SIZE (512 * 1024)

/* Import Changeset from an external authority
   format: d4:syncd[..]ee
   [..]:   ( 20:01234567890abcdefghij16:XXXXYYYY )+
*/
int add_changeset_to_tracker(uint8_t *data, size_t len) {
  ot_hash      *hash;
  uint8_t      *end = data + len;
  unsigned long peer_count;

  /* We do know, that the string is \n terminated, so it cant
     overflow */
  if (byte_diff(data, 8, "d4:syncd"))
    return -1;
  data += 8;

  while (1) {
    if (byte_diff(data, 3, "20:")) {
      if (byte_diff(data, 2, "ee"))
        return -1;
      return 0;
    }
    data += 3;
    hash  = (ot_hash *)data;
    data += sizeof(ot_hash);

    /* Scan string length indicator */
    data += (len = scan_ulong((char *)data, &peer_count));

    /* If no long was scanned, it is not divisible by 8, it is not
       followed by a colon or claims to need to much memory, we fail */
    if (!len || !peer_count || (peer_count & 7) || (*data++ != ':') || (data + peer_count > end))
      return -1;

    while (peer_count > 0) {
      add_peer_to_torrent(hash, (ot_peer *)data, 1);
      data       += 8;
      peer_count -= 8;
    }
  }
  return 0;
}

/* Proposed output format
   d4:syncd20:<info_hash>8*N:(xxxxyyyy)*Nee
*/
static void sync_make(int *iovec_entries, struct iovec **iovector) {
  int   bucket;
  char *r, *re;

  /* Setup return vector... */
  *iovec_entries = 0;
  *iovector      = NULL;
  if (!(r = iovec_increase(iovec_entries, iovector, OT_SYNC_CHUNK_SIZE)))
    return;

  /* ... and pointer to end of current output buffer.
     This works as a low watermark */
  re = r + OT_SYNC_CHUNK_SIZE;

  memmove(r, "d4:syncd", 8);
  r += 8;

  /* For each bucket... */
  for (bucket = 0; bucket < OT_BUCKET_COUNT; ++bucket) {
    /* Get exclusive access to that bucket */
    ot_vector *torrents_list = mutex_bucket_lock(bucket);
    size_t     tor_offset;

    /* For each torrent in this bucket.. */
    for (tor_offset = 0; tor_offset < torrents_list->size; ++tor_offset) {
      /* Address torrents members */
      ot_peerlist *peer_list  = (((ot_torrent *)(torrents_list->data))[tor_offset]).peer_list;
      ot_hash     *hash       = &(((ot_torrent *)(torrents_list->data))[tor_offset]).hash;
      const size_t byte_count = sizeof(ot_peer) * peer_list->changeset.size;

      /* If we reached our low watermark in buffer... */
      if (re - r <= (ssize_t)(/* strlen( "20:" ) == */ 3 + sizeof(ot_hash) + /* strlen_max( "%zd" ) == */ 12 + byte_count)) {

        /* Allocate a fresh output buffer at the end of our buffers list
           release bucket and return, if that fails */
        if (!(r = iovec_fix_increase_or_free(iovec_entries, iovector, r, OT_SYNC_CHUNK_SIZE)))
          return mutex_bucket_unlock(bucket);

        /* Adjust new end of output buffer */
        re = r + OT_SYNC_CHUNK_SIZE;
      }

      *r++ = '2';
      *r++ = '0';
      *r++ = ':';
      memmove(r, hash, sizeof(ot_hash));
      r += sizeof(ot_hash);
      r += sprintf(r, "%zd:", byte_count);
      memmove(r, peer_list->changeset.data, byte_count);
      r += byte_count;
    }

    /* All torrents done: release lock on currenct bucket */
    mutex_bucket_unlock(bucket);
  }

  /* Close bencoded sync dictionary */
  *r++ = 'e';
  *r++ = 'e';

  /* Release unused memory in current output buffer */
  iovec_fixlast(iovec_entries, iovector, r);
}

/* This is the entry point into this worker thread
   It grabs tasks from mutex_tasklist and delivers results back
*/
static void *sync_worker(void *args) {
  int           iovec_entries;
  struct iovec *iovector;

  args = args;

  while (1) {
    ot_tasktype tasktype = TASK_SYNC_OUT;
    ot_taskid   taskid   = mutex_workqueue_poptask(&tasktype);
    sync_make(&iovec_entries, &iovector);
    stats_issue_event(EVENT_SYNC_OUT, FLAG_TCP, iovec_length(&iovec_entries, &iovector));
    if (mutex_workqueue_pushresult(taskid, iovec_entries, iovector))
      iovec_free(&iovec_entries, &iovector);
  }
  return NULL;
}

static pthread_t thread_id;
void sync_init( ) {
  pthread_create( &thread_id, NULL, sync_worker, NULL );
}

void sync_deinit( ) {
  pthread_cancel( thread_id );
}

void sync_deliver( int64 socket ) {
  mutex_workqueue_pushtask( socket, TASK_SYNC_OUT );
}

#endif