tdb2: traverse and chainlock support.

[ccan] / ccan / tdb2 / traverse.c

diff --git a/ccan/tdb2/traverse.c b/ccan/tdb2/traverse.c
new file mode 100644 (file)
index 0000000..d30c24c
--- /dev/null
+++ b/ccan/tdb2/traverse.c
@@ -0,0 +1,125 @@
+ /* 
+   Trivial Database 2: traverse function.
+   Copyright (C) Rusty Russell 2010
+   
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "private.h"
+#include <ccan/likely/likely.h>
+
+static int64_t traverse(struct tdb_context *tdb, int ltype,
+                       tdb_traverse_func fn, void *p)
+{
+       uint64_t i, num, count = 0;
+       tdb_off_t off, prev_bucket;
+       struct tdb_used_record rec;
+       struct tdb_data k, d;
+       bool finish = false;
+
+       /* FIXME: Do we need to start at 0? */
+       prev_bucket = tdb_lock_list(tdb, 0, ltype, TDB_LOCK_WAIT);
+       if (prev_bucket != 0)
+               return -1;
+
+       num = (1ULL << tdb->header.v.hash_bits);
+
+       for (i = tdb_find_nonzero_off(tdb, hash_off(tdb, 0), num);
+            i != num && !finish;
+            i += tdb_find_nonzero_off(tdb, hash_off(tdb, i), num - i)) {
+               if (tdb_lock_list(tdb, i, ltype, TDB_LOCK_WAIT) != i)
+                       goto fail;
+
+               off = tdb_read_off(tdb, hash_off(tdb, i));
+               if (off == TDB_OFF_ERR) {
+                       tdb_unlock_list(tdb, i, ltype);
+                       goto fail;
+               }
+
+               /* This race can happen, but look again. */
+               if (off == 0) {
+                       tdb_unlock_list(tdb, i, ltype);
+                       continue;
+               }
+
+               /* Drop previous lock. */
+               tdb_unlock_list(tdb, prev_bucket, ltype);
+               prev_bucket = i;
+
+               if (tdb_read_convert(tdb, off, &rec, sizeof(rec)) != 0)
+                       goto fail;
+
+               k.dsize = rec_key_length(&rec);
+               d.dsize = rec_data_length(&rec);
+               if (ltype == F_RDLCK) {
+                       /* Read traverses can keep the lock. */
+                       k.dptr = (void *)tdb_access_read(tdb,
+                                                        off + sizeof(rec),
+                                                        k.dsize + d.dsize,
+                                                        false);
+               } else {
+                       k.dptr = tdb_alloc_read(tdb, off + sizeof(rec),
+                                               k.dsize + d.dsize);
+               }
+               if (!k.dptr)
+                       goto fail;
+               d.dptr = k.dptr + k.dsize;
+               count++;
+
+               if (ltype == F_WRLCK) {
+                       /* Drop lock before calling out. */
+                       tdb_unlock_list(tdb, i, ltype);
+               }
+
+               if (fn && fn(tdb, k, d, p))
+                       finish = true;
+
+               if (ltype == F_WRLCK) {
+                       free(k.dptr);
+                       /* Regain lock.  FIXME: Is this necessary? */
+                       if (tdb_lock_list(tdb, i, ltype, TDB_LOCK_WAIT) != i)
+                               return -1;
+
+                       /* This makes deleting under ourselves a bit nicer. */
+                       if (tdb_read_off(tdb, hash_off(tdb, i)) == off)
+                               i++;
+               } else {
+                       tdb_access_release(tdb, k.dptr);
+                       i++;
+               }
+       }
+
+       /* Drop final lock. */
+       tdb_unlock_list(tdb, prev_bucket, ltype);
+       return count;
+
+fail:
+       tdb_unlock_list(tdb, prev_bucket, ltype);
+       return -1;
+}
+
+int64_t tdb_traverse(struct tdb_context *tdb, tdb_traverse_func fn, void *p)
+{
+       return traverse(tdb, F_WRLCK, fn, p);
+}
+       
+int64_t tdb_traverse_read(struct tdb_context *tdb,
+                         tdb_traverse_func fn, void *p)
+{
+       int64_t ret;
+       bool was_ro = tdb->read_only;
+       tdb->read_only = true;
+       ret = traverse(tdb, F_RDLCK, fn, p);
+       tdb->read_only = was_ro;
+       return ret;
+}