+ return 1;
+} /* climb_level */
+
+
+static zint isamb_pp_forward_unode(ISAMB_PP pp, zint pos, const void *untilbuf)
+{ /* scans a upper node until it finds a child <= untilbuf */
+ /* pp points to the key value, as always. pos is the child read from */
+ /* the buffer */
+ /* if all values are too small, returns the last child in the node */
+ /* FIXME - this can be detected, and avoided by looking at the */
+ /* parent node, but that gets messy. Presumably the cost is */
+ /* pretty low anyway */
+ struct ISAMB_block *p = pp->block[pp->level];
+ const char *src=p->bytes + p->offset;
+ zint item_len;
+ int cmp;
+ zint nxtpos;
+#if ISAMB_DEBUG
+ int skips=0;
+ yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode starting "
+ "at level %d node %d ofs=%di sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ assert(!p->leaf);
+ assert(p->offset <= p->size);
+ if (p->offset == p->size) {
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning at end "
+ "at level %d node %d ofs=%di sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return pos; /* already at the end of it */
+ }
+ while(p->offset < p->size) {
+ decode_ptr(&src,&item_len);
+ cmp=(*pp->isamb->method->compare_item)(untilbuf,src);
+ src+=item_len;
+ decode_ptr(&src,&nxtpos);
+ if (cmp<pp->scope) /* cmp<2 */
+ {
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning a hit "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return pos;
+ } /* found one */
+ pos=nxtpos;
+ p->offset=src-(char*)p->bytes;
+ (pp->skipped_nodes[pp->maxlevel - pp->level -1])++;
+#if ISAMB_DEBUG
+ skips++;
+#endif
+ }
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_forward_unode returning at tail "
+ "at level %d node %d ofs=%d sz=%d skips=%d",
+ pp->level, p->pos, p->offset, p->size, skips);
+#endif
+ return pos; /* that's the last one in the line */
+
+} /* forward_unode */
+
+static void isamb_pp_descend_to_leaf(ISAMB_PP pp, ISAMB_P pos, const void *untilbuf)
+{ /* climbs down the tree, from pos, to the leftmost leaf */
+ struct ISAMB_block *p = pp->block[pp->level];
+ const char *src;
+ assert(!p->leaf);
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+ "starting at lev %d node %d ofs=%d lf=%d u=%p",
+ pp->level, p->pos, p->offset, p->leaf, untilbuf);
+#endif
+ if (untilbuf)
+ pos=isamb_pp_forward_unode(pp,pos,untilbuf);
+ ++(pp->level);
+ assert(pos);
+ p=open_block(pp->isamb, pos);
+ pp->block[pp->level]=p;
+ ++(pp->accessed_nodes[pp->maxlevel-pp->level]);
+ ++(pp->no_blocks);
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+ "got lev %d node %d lf=%d",
+ pp->level, p->pos, p->leaf);
+#endif
+ if (p->leaf)
+ return;
+ assert (p->offset==0 );
+ src=p->bytes + p->offset;
+ decode_ptr(&src, &pos);
+ p->offset=src-(char*)p->bytes;
+ isamb_pp_descend_to_leaf(pp,pos,untilbuf);
+#if ISAMB_DEBUG
+ yaz_log(YLOG_DEBUG,"isamb_pp_descend_to_leaf "
+ "returning at lev %d node %d ofs=%d lf=%d",
+ pp->level, p->pos, p->offset, p->leaf);
+#endif
+} /* descend_to_leaf */
+
+static int isamb_pp_find_next_leaf(ISAMB_PP pp)
+{ /* finds the next leaf by climbing up and down */
+ ISAMB_P pos;
+ if (!isamb_pp_climb_level(pp,&pos))
+ return 0;
+ isamb_pp_descend_to_leaf(pp, pos,0);