Function _fdb_iterator_seq_prev

src/iterator.cc:1646–1820

}

static fdb_status _fdb_iterator_seq_prev(fdb_iterator *iterator)
{
    size_t size_id, size_seq, seq_kv_len;
    uint8_t *seq_kv;
    uint64_t offset = BLK_NOT_FOUND;
    btree_result br = BTREE_RESULT_FAIL;
    hbtrie_result hr;
    struct docio_object _doc;
    struct docio_object _hbdoc;
    struct docio_handle *dhandle;
    struct snap_wal_entry *snap_item = NULL;
    fdb_seqnum_t seqnum;
    fdb_kvs_id_t kv_id;
    struct avl_node *cursor;

    size_id = sizeof(fdb_kvs_id_t);
    size_seq = sizeof(fdb_seqnum_t);
    seq_kv = alca(uint8_t, size_id + size_seq);

    // in forward iteration, cursor points to the next key to be returned
    // therefore, in return iteration, make cursor point to prev key
    if (iterator->direction == FDB_ITR_FORWARD) {
        if (iterator->status == FDB_ITR_IDX) {
            iterator->_offset = BLK_NOT_FOUND; // need to re-examine Trie/trees
        }
        if (iterator->tree_cursor) { // on turning direction
            if (iterator->status == FDB_ITR_WAL) { // skip 2 items
                iterator->tree_cursor = avl_prev(iterator->tree_cursor_prev);
            } else { // skip 1 item if the last doc was returned from main index
                iterator->tree_cursor = avl_prev(iterator->tree_cursor);
            }
            iterator->tree_cursor_prev = iterator->tree_cursor;
        }
    }
    iterator->tree_cursor = iterator->tree_cursor_prev;
start_seq:
    seqnum = iterator->_seqnum;
    dhandle = iterator->handle->dhandle;

    if (iterator->_offset == BLK_NOT_FOUND || // was iterating over btree
        !iterator->tree_cursor) { // WAL exhausted
        if (iterator->handle->kvs) { // multi KV instance mode
            hr = hbtrie_prev(iterator->seqtrie_iterator, seq_kv, &seq_kv_len,
                             (void *)&offset);
            if (hr == HBTRIE_RESULT_SUCCESS) {
                br = BTREE_RESULT_SUCCESS;
                buf2kvid(size_id, seq_kv, &kv_id);
                if (kv_id != iterator->handle->kvs->id) {
                    // iterator is beyond the boundary
                    br = BTREE_RESULT_FAIL;
                }
                memcpy(&seqnum, seq_kv + size_id, size_seq);
            } else {
                br = BTREE_RESULT_FAIL;
            }
        } else {
            br = btree_prev(iterator->seqtree_iterator, &seqnum,
                            (void *)&offset);