tdb2: implement tdb_firstkey/tdb_nextkey.

[ccan-lca-2011.git] / ccan / tdb2 / hash.c

diff --git a/ccan/tdb2/hash.c b/ccan/tdb2/hash.c
index 71ede4dbffda9e6a31786a9224d1e5ec16dc042a..0fd4774939d0399b9aa1706a3bf4d01b53c69bbd 100644 (file)
--- a/ccan/tdb2/hash.c
+++ b/ccan/tdb2/hash.c
@@ -131,14 +131,15 @@ bool is_subhash(tdb_off_t val)
 
 /* This is the core routine which searches the hashtable for an entry.
  * On error, no locks are held and TDB_OFF_ERR is returned.
- * Otherwise, hinfo is filled in.
+ * Otherwise, hinfo is filled in (and the optional tinfo).
  * If not found, the return value is 0.
  * If found, the return value is the offset, and *rec is the record. */
 tdb_off_t find_and_lock(struct tdb_context *tdb,
                        struct tdb_data key,
                        int ltype,
                        struct hash_info *h,
-                       struct tdb_used_record *rec)
+                       struct tdb_used_record *rec,
+                       struct traverse_info *tinfo)
 {
        uint32_t i, group;
        tdb_off_t hashtable;
@@ -158,6 +159,14 @@ tdb_off_t find_and_lock(struct tdb_context *tdb,
                return TDB_OFF_ERR;
 
        hashtable = offsetof(struct tdb_header, hashtable);
+       if (tinfo) {
+               tinfo->toplevel_group = group;
+               tinfo->num_levels = 1;
+               tinfo->levels[0].entry = 0;
+               tinfo->levels[0].hashtable = hashtable 
+                       + (group << TDB_HASH_GROUP_BITS) * sizeof(tdb_off_t);
+               tinfo->levels[0].total_buckets = 1 << TDB_HASH_GROUP_BITS;
+       }
 
        while (likely(h->hash_used < 64)) {
                /* Read in the hash group. */
@@ -172,9 +181,23 @@ tdb_off_t find_and_lock(struct tdb_context *tdb,
                if (is_subhash(h->group[h->home_bucket])) {
                        hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
                                + sizeof(struct tdb_used_record);
+                       if (tinfo) {
+                               /* When we come back, use *next* bucket */
+                               tinfo->levels[tinfo->num_levels-1].entry
+                                       += h->home_bucket + 1;
+                       }
                        group = use_bits(h, TDB_SUBLEVEL_HASH_BITS
                                         - TDB_HASH_GROUP_BITS);
                        h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
+                       if (tinfo) {
+                               tinfo->levels[tinfo->num_levels].hashtable
+                                       = hashtable;
+                               tinfo->levels[tinfo->num_levels].total_buckets
+                                       = 1 << TDB_SUBLEVEL_HASH_BITS;
+                               tinfo->levels[tinfo->num_levels].entry
+                                       = group << TDB_HASH_GROUP_BITS;
+                               tinfo->num_levels++;
+                       }
                        continue;
                }
 
@@ -189,8 +212,14 @@ tdb_off_t find_and_lock(struct tdb_context *tdb,
                        if (!h->group[h->found_bucket])
                                break;
 
-                       if (match(tdb, h, &key, h->group[h->found_bucket], rec))
+                       if (match(tdb, h, &key, h->group[h->found_bucket],
+                                 rec)) {
+                               if (tinfo) {
+                                       tinfo->levels[tinfo->num_levels-1].entry
+                                               += h->found_bucket;
+                               }
                                return h->group[h->found_bucket] & TDB_OFF_MASK;
+                       }
                }
                /* Didn't find it: h indicates where it would go. */
                return 0;
@@ -470,17 +499,18 @@ again:
                if (unlikely(val == TDB_OFF_ERR))
                        return TDB_OFF_ERR;
 
+               off = val & TDB_OFF_MASK;
+
                /* This makes the delete-all-in-traverse case work
                 * (and simplifies our logic a little). */
-               if (val == tinfo->prev)
+               if (off == tinfo->prev)
                        continue;
 
                tlevel->entry = i;
-               off = val & TDB_OFF_MASK;
 
                if (!is_subhash(val)) {
                        /* Found one. */
-                       tinfo->prev = val;
+                       tinfo->prev = off;
                        return off;
                }
 
@@ -572,3 +602,41 @@ int first_in_hash(struct tdb_context *tdb, int ltype,
 
        return next_in_hash(tdb, ltype, tinfo, kbuf, dlen);
 }
+
+TDB_DATA tdb_firstkey(struct tdb_context *tdb)
+{
+       struct traverse_info tinfo;
+       struct tdb_data k;
+       switch (first_in_hash(tdb, F_RDLCK, &tinfo, &k, NULL)) {
+       case 1:
+               return k;
+       case 0:
+               tdb->ecode = TDB_SUCCESS;
+               /* Fall thru... */
+       default:
+               return tdb_null;
+       }
+}              
+
+/* We lock twice, not very efficient.  We could keep last key & tinfo cached. */
+TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA key)
+{
+       struct traverse_info tinfo;
+       struct hash_info h;
+       struct tdb_used_record rec;
+
+       tinfo.prev = find_and_lock(tdb, key, F_RDLCK, &h, &rec, &tinfo);
+       if (unlikely(tinfo.prev == TDB_OFF_ERR))
+               return tdb_null;
+       tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_RDLCK);
+
+       switch (next_in_hash(tdb, F_RDLCK, &tinfo, &key, NULL)) {
+       case 1:
+               return key;
+       case 0:
+               tdb->ecode = TDB_SUCCESS;
+               /* Fall thru... */
+       default:
+               return tdb_null;
+       }
+}