Don't clear the bitfield for blocks it's possible we have, even though

the resume file and content aren't synchronized. Save the resumefile
every 15 seconds for torrents we're downloading. This way we don't have
to redownload much content because of crash or whatnot. Not that btpd would
crash :)
Also, as there were probably no point in fsync'ing the content when we closed
the write stream, that is not done anymore.

btpd/content.c

@@ -79,6 +79,8 @@ struct content {
 
     struct bt_stream *rds;
     struct bt_stream *wrs;
+
+    struct event save_timer;
 };
 
 #define ZEROBUFLEN (1 << 14)
@@ -179,6 +181,20 @@ cm_save(struct torrent *tp)
     add_todo(cm, op);
 }
 
+static void
+cm_write_done(struct torrent *tp)
+{
+    int err;
+    struct content *cm = tp->cm;
+
+    if ((err = bts_close(cm->wrs)) != 0)
+        btpd_err("Error closing write stream for %s (%s).\n", tp->relpath,
+            strerror(err));
+    cm->wrs = NULL;
+    event_del(&cm->save_timer);
+    cm_save(tp);
+}
+
 void
 cm_stop(struct torrent *tp)
 {
@@ -195,16 +211,27 @@ cm_stop(struct torrent *tp)
             free(op);
         }
         pthread_mutex_unlock(&m_long_comm.lock);
-    } else if (cm->npieces_got < tp->meta.npieces)
-        cm_save(tp);
+    } else if (!cm_full(tp))
+        cm_write_done(tp);
 
     if (BTPDQ_EMPTY(&cm->todoq))
         cm_destroy(tp);
 }
 
+#define SAVE_INTERVAL (& (struct timeval) { 15, 0 })
+
+static void
+save_timer_cb(int fd, short type, void *arg)
+{
+    struct torrent *tp = arg;
+    event_add(&tp->cm->save_timer, SAVE_INTERVAL);
+    cm_save(tp);
+}
+
 static void
 cm_td_cb(void *arg)
 {
+    int err;
     struct cm_op *op = arg;
     struct torrent *tp = op->tp;
     struct content *cm = tp->cm;
@@ -220,6 +247,12 @@ cm_td_cb(void *arg)
     case CM_START:
         if (cm->active) {
             assert(!op->u.start.cancel);
+            if (!cm_full(tp)) {
+                if ((err = bts_open(&cm->wrs, &tp->meta, fd_cb_wr, tp)) != 0)
+                    btpd_err("Couldn't open write stream for %s (%s).\n",
+                        tp->relpath, strerror(err));
+                event_add(&cm->save_timer, SAVE_INTERVAL);
+            }
             torrent_on_cm_started(tp);
         }
         break;
@@ -231,7 +264,7 @@ cm_td_cb(void *arg)
             if (tp->net != NULL)
                 dl_on_ok_piece(op->tp->net, op->u.test.piece);
             if (cm_full(tp))
-                cm_save(tp);
+                cm_write_done(tp);
         } else {
             cm->ncontent_bytes -= torrent_piece_size(tp, op->u.test.piece);
             bzero(cm->block_field + op->u.test.piece * cm->bppbf, cm->bppbf);
@@ -270,6 +303,8 @@ cm_start(struct torrent *tp)
         btpd_err("Error opening stream (%s).\n", strerror(err));
     tp->cm = cm;
 
+    evtimer_set(&cm->save_timer, save_timer_cb, tp);
+
     struct cm_op *op = btpd_calloc(1, sizeof(*op));
     op->tp = tp;
     op->type = CM_START;
@@ -572,14 +607,14 @@ load_resume(struct torrent *tp, struct stat sbs[])
         if (fscanf(fp, "%qd %ld\n", &size, &time) != 2)
             goto invalid;
         if (sbs[i].st_size != size || sbs[i].st_mtime != time)
-            goto invalid;
+            err = EINVAL;
     }
     if (fread(tp->cm->piece_field, 1, pfsiz, fp) != pfsiz)
         goto invalid;
     if (fread(tp->cm->block_field, 1, bfsiz, fp) != bfsiz)
         goto invalid;
     fclose(fp);
-    return 0;
+    return err;
 invalid:
     fclose(fp);
     bzero(tp->cm->piece_field, pfsiz);
@@ -610,33 +645,13 @@ save_resume(struct torrent *tp)
 static void
 cm_td_save(struct cm_op *op)
 {
-    int err;
-    struct torrent *tp = op->tp;
-    struct content *cm = tp->cm;
-    struct bt_stream *bts = cm->wrs;
-
-    cm->wrs = NULL;
-    if ((err = bts_close(bts)) != 0)
-        goto out;
-
-    for (int i = 0; i < tp->meta.nfiles; i++) {
-        int lerr;
-        if ((lerr = vfsync("library/%s/content/%s", tp->relpath,
-                 tp->meta.files[i])) != 0 && lerr != ENOENT)
-            err = lerr;
-    }
-    if (err != 0)
-        goto out;
-    save_resume(tp);
-out:
-    if (err != 0)
-        op->error = 1;
+    save_resume(op->tp);
 }
 
 static void
 cm_td_start(struct cm_op *op)
 {
-    int err;
+    int err, resume_clean = 0, tested_torrent = 0;
     struct stat sbs[op->tp->meta.nfiles];
     struct torrent *tp = op->tp;
     struct content *cm = tp->cm;
@@ -644,7 +659,8 @@ cm_td_start(struct cm_op *op)
     if ((err = stat_and_adjust(op->tp, sbs)) != 0)
         goto out;
 
-    if (load_resume(tp, sbs) != 0) {
+    resume_clean = load_resume(tp, sbs) == 0;
+    if (!resume_clean) {
         memset(cm->pos_field, 0xff, ceil(tp->meta.npieces / 8.0));
         off_t off = 0;
         for (int i = 0; i < tp->meta.nfiles; i++) {
@@ -654,6 +670,8 @@ cm_td_start(struct cm_op *op)
                     tp->meta.piece_length;
                 while (start <= end) {
                     clear_bit(cm->pos_field, start);
+                    clear_bit(cm->piece_field, start);
+                    bzero(cm->block_field + start * cm->bppbf, cm->bppbf);
                     start++;
                 }
             } else if (sbs[i].st_size < tp->meta.files[i].length) {
@@ -672,7 +690,7 @@ cm_td_start(struct cm_op *op)
             goto out;
         if ((err = test_torrent(tp, &op->u.start.cancel)) != 0)
             goto out;
-        save_resume(tp);
+        tested_torrent = 1;
     }
 
     bzero(cm->pos_field, ceil(tp->meta.npieces / 8.0));
@@ -694,10 +712,13 @@ cm_td_start(struct cm_op *op)
             }
         }
         if (nblocks_got == nblocks) {
-            int ok;
-            if (((err = test_piece(tp, piece, piece, &ok)) != 0
-                    || op->u.start.cancel))
-                goto out;
+            resume_clean = 0;
+            int ok = 0;
+            if (!tested_torrent) {
+                if (((err = test_piece(tp, piece, piece, &ok)) != 0
+                        || op->u.start.cancel))
+                    goto out;
+            }
             if (ok) {
                 set_bit(cm->pos_field, piece);
                 set_bit(cm->piece_field, piece);
@@ -707,9 +728,9 @@ cm_td_start(struct cm_op *op)
             set_bit(cm->pos_field, piece);
     }
 
-    if (cm->npieces_got < tp->meta.npieces)
-        if ((err = bts_open(&cm->wrs, &tp->meta, fd_cb_wr, tp)) != 0)
-            goto out;
+    if (!resume_clean)
+        save_resume(tp);
+
 out:
     if (!op->u.start.cancel && err != 0)
         op->error = 1;