+#define NEW_FORWARD 1
+
+#if NEW_FORWARD == 1
+
+/*
+#undef ISAMB_DEBUB
+#define ISAMB_DEBUG 1
+*/
+static int isamb_pp_on_right_node(ISAMB_PP pp, int level, const void *untilbuf)
+{ /* looks one node higher to see if we should be on this node at all */
+ /* useful in backing off quickly, and in avoiding tail descends */
+ /* call with pp->level to begin with */
+ struct ISAMB_block *p;
+ int cmp;
+ char *src;
+ int item_len;
+ assert(level>=0);
+ if ( level == 0) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_on_right returning true for root");
+#endif
+ return 1; /* we can never skip the root node */
+ }
+ level--;
+ p=pp->block[level];
+ assert(p->offset <= p->size);
+ if (p->offset < p->size )
+ {
+ assert(p->offset>0);
+ src=p->bytes + p->offset;
+ decode_ptr(&src,&item_len);
+#if ISAMB_DEBUG
+ (*pp->isamb->method->log_item)(LOG_DEBUG,untilbuf,"on_leaf: until");
+ (*pp->isamb->method->log_item)(LOG_DEBUG,src,"on_leaf: value");
+#endif
+ cmp=(*pp->isamb->method->compare_item)(untilbuf,src);
+ if (cmp<2) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_on_right returning true "
+ "cmp=%d lev=%d ofs=%d",cmp,level,p->offset);
+#endif
+ return 1;
+ }
+ else {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_on_right returning false "
+ "cmp=%d lev=%d ofs=%d",cmp,level,p->offset);
+#endif
+ return 0;
+ }
+ }
+ else {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_on_right at tail, looking higher "
+ "lev=%d",level);
+#endif
+ return isamb_pp_on_right_node(pp, level, untilbuf);
+ }
+} /* isamb_pp_on_right_node */
+
+static int isamb_pp_read_on_leaf(ISAMB_PP pp, void *buf)
+{ /* reads the next item on the current leaf, returns 0 if end of leaf*/
+ struct ISAMB_block *p = pp->block[pp->level];
+ char *dst;
+ char *src;
+ assert(pp);
+ assert(buf);
+ if (p->offset == p->size) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_read_on_leaf returning 0 on node %d",p->pos);
+#endif
+ return 0; /* at end of leaf */
+ }
+ src=p->bytes + p->offset;
+ dst=buf;
+ (*pp->isamb->method->code_item)
+ (ISAMC_DECODE, p->decodeClientData,&dst, &src);
+ p->offset = src - (char*) p->bytes;
+ /*
+#if ISAMB_DEBUG
+ (*pp->isamb->method->log_item)(LOG_DEBUG, buf, "read_on_leaf returning 1");
+#endif
+*/
+ return 1;
+} /* read_on_leaf */
+
+static int isamb_pp_forward_on_leaf(ISAMB_PP pp, void *buf, const void *untilbuf)
+{ /* forwards on the current leaf, returns 0 if not found */
+ int cmp;
+ int skips=0;
+ while (1){
+ if (!isamb_pp_read_on_leaf(pp,buf))
+ return 0;
+ /* FIXME - this is an extra function call, inline the read? */
+ cmp=(*pp->isamb->method->compare_item)(untilbuf,buf);
+ if (cmp <2){ /* found a good one */
+#if ISAMB_DEBUG
+ if (skips)
+ logf(LOG_DEBUG, "isam_pp_fwd_on_leaf skipped %d items",skips);
+#endif
+ pp->returned_numbers++;
+ return 1;
+ }
+ if (!skips)
+ if (!isamb_pp_on_right_node(pp, pp->level, untilbuf))
+ return 0; /* never mind the rest of this leaf */
+ pp->skipped_numbers++;
+ skips++;
+ }
+} /* forward_on_leaf */
+
+static int isamb_pp_climb_level(ISAMB_PP pp, int *pos)
+{ /* climbs higher in the tree, until finds a level with data left */
+ /* returns the node to (consider to) descend to in *pos) */
+ struct ISAMB_block *p = pp->block[pp->level];
+ char *src;
+ int item_len;
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_climb_level starting "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ assert(pp->level >= 0);
+ assert(p->offset <= p->size);
+ if (pp->level==0)
+ {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_climb_level returning 0 at root");
+#endif
+ return 0;
+ }
+ assert(pp->level>0);
+ close_block(pp->isamb, pp->block[pp->level]);
+ pp->block[pp->level]=0;
+ (pp->level)--;
+ p=pp->block[pp->level];
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_climb_level climbed to level %d node %d ofs=%d",
+ pp->level, p->pos, p->offset);
+#endif
+ assert(!p->leaf);
+ assert(p->offset <= p->size);
+ if (p->offset == p->size ) {
+ /* we came from the last pointer, climb on */
+ if (!isamb_pp_climb_level(pp,pos))
+ return 0;
+ p=pp->block[pp->level];
+ }
+ else
+ {
+ /* skip the child we just came from */
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isam_pp_climb_level: skipping lev=%d ofs=%d sz=%d",
+ pp->level, p->offset, p->size);
+#endif
+ assert (p->offset < p->size );
+ src=p->bytes + p->offset;
+ decode_ptr(&src, &item_len);
+ src += item_len;
+ decode_ptr(&src, pos);
+ p->offset=src - (char *)p->bytes;
+
+ }
+ return 1;
+} /* climb_level */
+
+
+static int isamb_pp_forward_unode(ISAMB_PP pp, int 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];
+ char *src=p->bytes + p->offset;
+ int item_len;
+ int cmp;
+ int nxtpos;
+#if ISAMB_DEBUG
+ int skips=0;
+ logf(LOG_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
+ logf(LOG_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<2)
+ {
+#if ISAMB_DEBUG
+ logf(LOG_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
+ logf(LOG_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, int pos, const void *untilbuf)
+{ /* climbs down the tree, from pos, to the leftmost leaf */
+ struct ISAMB_block *p = pp->block[pp->level];
+ char *src;
+ assert(!p->leaf);
+#if ISAMB_DEBUG
+ logf(LOG_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
+ logf(LOG_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
+ logf(LOG_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 */
+ int pos;
+ if (!isamb_pp_climb_level(pp,&pos))
+ return 0;
+ isamb_pp_descend_to_leaf(pp, pos,0);
+ return 1;
+}
+
+static int isamb_pp_climb_desc(ISAMB_PP pp, void *buf, const void *untilbuf)
+{ /* climbs up and descends to a leaf where values >= *untilbuf are found */
+ int pos;
+#if ISAMB_DEBUG
+ struct ISAMB_block *p = pp->block[pp->level];
+ logf(LOG_DEBUG,"isamb_pp_climb_desc starting "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ if (!isamb_pp_climb_level(pp,&pos))
+ return 0;
+ /* see if it would pay to climb one higher */
+ if (!isamb_pp_on_right_node(pp, pp->level, untilbuf))
+ if (!isamb_pp_climb_level(pp,&pos))
+ return 0;
+ isamb_pp_descend_to_leaf(pp, pos,untilbuf);
+#if ISAMB_DEBUG
+ p = pp->block[pp->level];
+ logf(LOG_DEBUG,"isamb_pp_climb_desc done "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return 1;
+} /* climb_desc */
+
+int isamb_pp_forward (ISAMB_PP pp, void *buf, const void *untilbuf)
+{
+#if ISAMB_DEBUG
+ struct ISAMB_block *p = pp->block[pp->level];
+ assert(p->leaf);
+ logf(LOG_DEBUG,"isamb_pp_forward starting "
+ "at level %d node %d ofs=%d sz=%d u=%p",
+ pp->level, p->pos, p->offset, p->size,untilbuf);
+#endif
+ if (untilbuf) {
+ if (isamb_pp_forward_on_leaf( pp, buf, untilbuf)) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_forward (f) returning (A) "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return 1;
+ }
+ if (! isamb_pp_climb_desc( pp, buf, untilbuf)) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_forward (f) returning notfound (B) "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return 0; /* could not find a leaf */
+ }
+ do{
+ if (isamb_pp_forward_on_leaf( pp, buf, untilbuf)) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_forward (f) returning (C) "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return 1;
+ }
+ }while ( isamb_pp_find_next_leaf(pp));
+ return 0; /* could not find at all */
+ }
+ else { /* no untilbuf, a straight read */
+ /* FIXME - this should be moved
+ * directly into the pp_read */
+ /* keeping here now, to keep same
+ * interface as the old fwd */
+ if (isamb_pp_read_on_leaf( pp, buf)) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_forward (read) returning (D) "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return 1;
+ }
+ if (isamb_pp_find_next_leaf(pp)) {
+#if ISAMB_DEBUG
+ logf(LOG_DEBUG,"isamb_pp_forward (read) returning (E) "
+ "at level %d node %d ofs=%d sz=%d",
+ pp->level, p->pos, p->offset, p->size);
+#endif
+ return isamb_pp_read_on_leaf(pp, buf);
+ }
+ else
+ return 0;
+ }
+} /* isam_pp_forward (new version) */
+
+#elif NEW_FORWARD == 0
+