indexf.c

Go to the documentation of this file.

/****************************************************************************
 * MODULE:       R-Tree library
 *
 * AUTHOR(S):    Antonin Guttman - original code
 *               Daniel Green (green@superliminal.com) - major clean-up
 *                               and implementation of bounding spheres
 *               Markus Metz - file-based and memory-based R*-tree
 *
 * PURPOSE:      Multidimensional index
 *
 * SPDX-FileCopyrightText: 2001 GRASS Development Team
 * SPDX-License-Identifier: GPL-2.0-or-later
 *****************************************************************************/
 
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <assert.h>
#include <grass/gis.h>
#include "index.h"
 
int RTreeValidChildF(union RTree_Child *child)
{
    return (child->pos > -1);
}
 
/*
 * Search in an index tree for all data rectangles that
 * overlap the argument rectangle.
 * Return the number of qualifying data rects.
 */
int RTreeSearchF(struct RTree *t, struct RTree_Rect *r, SearchHitCallback *shcb,
                 void *cbarg)
{
    struct RTree_Node *n;
    int hitCount = 0, notfound, currlevel;
    int i;
    int top = 0;
    struct nstack *s = t->ns;
 
    /* stack size of t->rootlevel + 1 is enough because of depth first search */
    /* only one node per level on stack at any given time */
 
    /* add root node position to stack */
    currlevel = t->rootlevel;
    s[top].pos = t->rootpos;
    s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
    s[top].branch_id = i = 0;
 
    while (top >= 0) {
        n = s[top].sn;
        if (s[top].sn->level > 0) { /* this is an internal node in the tree */
            notfound = 1;
            currlevel = s[top].sn->level - 1;
            for (i = s[top].branch_id; i < t->nodecard; i++) {
                if (s[top].sn->branch[i].child.pos > -1 &&
                    RTreeOverlap(r, &(s[top].sn->branch[i].rect), t)) {
                    s[top++].branch_id = i + 1;
                    /* add next node to stack */
                    s[top].pos = n->branch[i].child.pos;
                    s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
                    s[top].branch_id = 0;
                    notfound = 0;
                    break;
                }
            }
            if (notfound) {
                /* nothing else found, go back up */
                s[top].branch_id = t->nodecard;
                top--;
            }
        }
        else { /* this is a leaf node */
            for (i = 0; i < t->leafcard; i++) {
                if (s[top].sn->branch[i].child.id &&
                    RTreeOverlap(r, &(s[top].sn->branch[i].rect), t)) {
                    hitCount++;
                    if (shcb) { /* call the user-provided callback */
                        if (!shcb(s[top].sn->branch[i].child.id,
                                  &(s[top].sn->branch[i].rect), cbarg)) {
                            /* callback wants to terminate search early */
                            return hitCount;
                        }
                    }
                }
            }
            top--;
        }
    }
 
    return hitCount;
}
 
/*
 * Inserts a new data rectangle into the index structure.
 * Non-recursively descends tree, propagates splits back up.
 * Returns 0 if node was not split.  Old node updated.
 * If node was split, returns 1 and sets the pointer pointed to by
 * new_node to point to the new node.  Old node updated to become one of two.
 * The level argument specifies the number of steps up from the leaf
 * level to insert; e.g. a data rectangle goes in at level = 0.
 */
static int RTreeInsertRect2F(struct RTree_Rect *r, union RTree_Child child,
                             int level, struct RTree_Node *newnode,
                             off_t *newnode_pos, struct RTree *t,
                             struct RTree_ListBranch **ee, char *overflow)
{
    int i, currlevel;
    struct RTree_Node *n, *n2;
    struct RTree_Rect *cover;
    int top = 0, down = 0;
    int result;
    struct RTree_Branch *b = &(t->tmpb2);
    struct nstack *s = t->ns;
 
    struct RTree_Rect *nr = &(t->orect);
 
    n2 = newnode;
 
    /* add root node position to stack */
    currlevel = t->rootlevel;
    s[top].pos = t->rootpos;
    s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
 
    /* go down to level of insertion */
    while (s[top].sn->level > level) {
        n = s[top].sn;
        currlevel = s[top].sn->level - 1;
        i = RTreePickBranch(r, n, t);
        s[top++].branch_id = i;
        /* add next node to stack */
        s[top].pos = n->branch[i].child.pos;
        s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
    }
 
    /* Have reached level for insertion. Add rect, split if necessary */
    RTreeCopyRect(&(b->rect), r, t);
    /* child field of leaves contains tid of data record */
    b->child = child;
    /* add branch, may split node or remove branches */
    cover = NULL;
    if (top)
        cover = &(s[top - 1].sn->branch[s[top - 1].branch_id].rect);
    result = RTreeAddBranch(b, s[top].sn, &n2, ee, cover, overflow, t);
    /* update node */
    RTreeNodeChanged(s[top].sn, s[top].pos, t);
    /* write out new node if node was split */
    if (result == 1) {
        *newnode_pos = RTreeGetNodePos(t);
        RTreeWriteNode(n2, t);
        t->n_nodes++;
    }
 
    /* go back up */
    while (top) {
        down = top--;
        i = s[top].branch_id;
        if (result == 0) { /* branch was added */
            if (RTreeExpandRect(&(s[top].sn->branch[i].rect), r, t)) {
                RTreeNodeChanged(s[top].sn, s[top].pos, t);
            }
        }
        else if (result == 2) { /* branches were removed */
            /* get node cover of previous node */
            RTreeNodeCover(s[down].sn, nr, t);
            /* rewrite rect */
            if (!RTreeCompareRect(nr, &(s[top].sn->branch[i].rect), t)) {
                RTreeCopyRect(&(s[top].sn->branch[i].rect), nr, t);
                RTreeNodeChanged(s[top].sn, s[top].pos, t);
            }
        }
        else if (result == 1) { /* node was split */
            /* get node cover of previous node */
            RTreeNodeCover(s[down].sn, &(s[top].sn->branch[i].rect), t);
            /* add new branch for new node previously added by RTreeAddBranch()
             */
            b->child.pos = *newnode_pos;
            RTreeNodeCover(n2, &(b->rect), t);
 
            /* add branch, may split node or remove branches */
            cover = NULL;
            if (top)
                cover = &(s[top - 1].sn->branch[s[top - 1].branch_id].rect);
            result = RTreeAddBranch(b, s[top].sn, &n2, ee, cover, overflow, t);
 
            /* update node */
            RTreeNodeChanged(s[top].sn, s[top].pos, t);
 
            /* write out new node if node was split */
            if (result == 1) {
                *newnode_pos = RTreeGetNodePos(t);
                RTreeWriteNode(n2, t);
                t->n_nodes++;
            }
        }
    }
 
    return result;
}
 
/*
 * Insert a data rectangle into an index structure.
 * RTreeInsertRect provides for splitting the root;
 * returns 1 if root was split, 0 if it was not.
 * The level argument specifies the number of steps up from the leaf
 * level to insert; e.g. a data rectangle goes in at level = 0.
 * RTreeInsertRect2 does the actual insertion.
 */
int RTreeInsertRectF(struct RTree_Rect *r, union RTree_Child child, int level,
                     struct RTree *t)
{
    struct RTree_ListBranch *reInsertList = NULL;
    struct RTree_ListBranch *e;
    int result;
    char overflow[MAXLEVEL];
    struct RTree_Branch *b = &(t->tmpb1);
    off_t newnode_pos = -1;
 
    struct RTree_Node *oldroot;
    static struct RTree_Node *newroot = NULL, *newnode = NULL;
 
    if (!newroot) {
        newroot = RTreeAllocNode(t, 1);
        newnode = RTreeAllocNode(t, 1);
    }
 
    /* R*-tree forced reinsertion: for each level only once */
    memset(overflow, t->overflow, MAXLEVEL);
 
    result = RTreeInsertRect2F(r, child, level, newnode, &newnode_pos, t,
                               &reInsertList, overflow);
 
    if (result == 1) { /* root split */
        oldroot = RTreeGetNode(t->rootpos, t->rootlevel, t);
        /* grow a new root, & tree taller */
        t->rootlevel++;
        RTreeInitNode(t, newroot, NODETYPE(t->rootlevel, t->fd));
        newroot->level = t->rootlevel;
        /* branch for old root */
        RTreeNodeCover(oldroot, &(b->rect), t);
        b->child.pos = t->rootpos;
        RTreeAddBranch(b, newroot, NULL, NULL, NULL, NULL, t);
        /* branch for new node created by RTreeInsertRect2() */
        RTreeNodeCover(newnode, &(b->rect), t);
        b->child.pos = newnode_pos; /* offset to new node as returned by
                                       RTreeInsertRect2F() */
        RTreeAddBranch(b, newroot, NULL, NULL, NULL, NULL, t);
        /* write new root node */
        t->rootpos = RTreeGetNodePos(t);
        RTreeWriteNode(newroot, t);
        t->n_nodes++;
 
        return result;
    }
 
    if (result == 2) { /* branches were removed */
        while (reInsertList) {
            /* get next branch in list */
            RTreeCopyBranch(b, &(reInsertList->b), t);
            level = reInsertList->level;
            e = reInsertList;
            reInsertList = reInsertList->next;
            RTreeFreeListBranch(e);
            /* reinsert branches */
            result =
                RTreeInsertRect2F(&(b->rect), b->child, level, newnode,
                                  &newnode_pos, t, &reInsertList, overflow);
 
            if (result == 1) { /* root split */
                oldroot = RTreeGetNode(t->rootpos, t->rootlevel, t);
                /* grow a new root, & tree taller */
                t->rootlevel++;
                RTreeInitNode(t, newroot, NODETYPE(t->rootlevel, t->fd));
                newroot->level = t->rootlevel;
                /* branch for old root */
                RTreeNodeCover(oldroot, &(b->rect), t);
                b->child.pos = t->rootpos;
                RTreeAddBranch(b, newroot, NULL, NULL, NULL, NULL, t);
                /* branch for new node created by RTreeInsertRect2() */
                RTreeNodeCover(newnode, &(b->rect), t);
                b->child.pos = newnode_pos;
                RTreeAddBranch(b, newroot, NULL, NULL, NULL, NULL, t);
                /* write new root node */
                t->rootpos = RTreeGetNodePos(t);
                RTreeWriteNode(newroot, t);
                t->n_nodes++;
            }
        }
    }
 
    return result;
}
 
/*
 * Delete a rectangle from non-root part of an index structure.
 * Called by RTreeDeleteRect.  Descends tree non-recursively,
 * merges branches on the way back up.
 * Returns 1 if record not found, 0 if success.
 */
static int RTreeDeleteRect2F(struct RTree_Rect *r, union RTree_Child child,
                             struct RTree *t, struct RTree_ListNode **ee)
{
    int i, notfound = 1, currlevel;
    struct RTree_Node *n;
    int top = 0, down = 0;
    int minfill;
    struct nstack *s = t->ns;
 
    struct RTree_Rect *nr = &(t->orect);
 
    /* add root node position to stack */
    currlevel = t->rootlevel;
    s[top].pos = t->rootpos;
    s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
    s[top].branch_id = 0;
 
    while (notfound && top >= 0) {
        /* go down to level 0, remember path */
        if (s[top].sn->level > 0) {
            n = s[top].sn;
            currlevel = s[top].sn->level - 1;
            for (i = s[top].branch_id; i < t->nodecard; i++) {
                if (n->branch[i].child.pos > -1 &&
                    RTreeOverlap(r, &(n->branch[i].rect), t)) {
                    s[top++].branch_id = i + 1;
                    /* add next node to stack */
                    s[top].pos = n->branch[i].child.pos;
                    s[top].sn = RTreeGetNode(s[top].pos, currlevel, t);
                    s[top].branch_id = 0;
 
                    notfound = 0;
                    break;
                }
            }
            if (notfound) {
                /* nothing else found, go back up */
                s[top].branch_id = t->nodecard;
                top--;
            }
            else /* found a way down but not yet the item */
                notfound = 1;
        }
        else {
            for (i = 0; i < t->leafcard; i++) {
                if (s[top].sn->branch[i].child.id &&
                    s[top].sn->branch[i].child.id ==
                        child.id) { /* found item */
                    RTreeDisconnectBranch(s[top].sn, i, t);
                    RTreeNodeChanged(s[top].sn, s[top].pos, t);
                    t->n_leafs--;
                    notfound = 0;
                    break;
                }
            }
            if (notfound) /* continue searching */
                top--;
        }
    }
 
    if (notfound) {
        return notfound;
    }
 
    /* go back up */
    while (top) {
        down = top;
        top--;
        i = s[top].branch_id - 1;
 
        minfill = (s[down].sn->level ? t->min_node_fill : t->min_leaf_fill);
        if (s[down].sn->count >= minfill) {
            /* just update node cover */
            RTreeNodeCover(s[down].sn, nr, t);
            /* rewrite rect */
            if (!RTreeCompareRect(nr, &(s[top].sn->branch[i].rect), t)) {
                RTreeCopyRect(&(s[top].sn->branch[i].rect), nr, t);
                RTreeNodeChanged(s[top].sn, s[top].pos, t);
            }
        }
        else {
            /* not enough entries in child, eliminate child node */
            n = RTreeAllocNode(t, s[down].sn->level);
            /* copy node */
            RTreeCopyNode(n, s[down].sn, t);
            RTreeAddNodePos(s[down].pos, s[down].sn->level, t);
            RTreeReInsertNode(n, ee);
            RTreeDisconnectBranch(s[top].sn, i, t);
 
            RTreeNodeChanged(s[top].sn, s[top].pos, t);
        }
    }
 
    return notfound;
}
 
/*
 * should be called by RTreeDeleteRect() only
 *
 * Delete a data rectangle from an index structure.
 * Pass in a pointer to a Rect, the tid of the record, ptr RTree.
 * Returns 1 if record not found, 0 if success.
 * RTreeDeleteRect1 provides for eliminating the root.
 */
int RTreeDeleteRectF(struct RTree_Rect *r, union RTree_Child child,
                     struct RTree *t)
{
    int i;
    struct RTree_Node *n;
    struct RTree_ListNode *e, *reInsertList = NULL;
 
    if (!RTreeDeleteRect2F(r, child, t, &reInsertList)) {
        /* found and deleted a data item */
 
        /* reinsert any branches from eliminated nodes */
        while (reInsertList) {
            t->n_nodes--;
            n = reInsertList->node;
            if (n->level > 0) { /* reinsert node branches */
                for (i = 0; i < t->nodecard; i++) {
                    if (n->branch[i].child.pos > -1) {
                        RTreeInsertRectF(&(n->branch[i].rect),
                                         n->branch[i].child, n->level, t);
                    }
                }
            }
            else { /* reinsert leaf branches */
                for (i = 0; i < t->leafcard; i++) {
                    if (n->branch[i].child.id) {
                        RTreeInsertRectF(&(n->branch[i].rect),
                                         n->branch[i].child, n->level, t);
                    }
                }
            }
            e = reInsertList;
            reInsertList = reInsertList->next;
            RTreeFreeNode(e->node);
            RTreeFreeListNode(e);
        }
 
        /* check for redundant root (not leaf, 1 child) and eliminate */
        n = RTreeGetNode(t->rootpos, t->rootlevel, t);
 
        if (n->count == 1 && n->level > 0) {
            for (i = 0; i < t->nodecard; i++) {
                if (n->branch[i].child.pos > -1)
                    break;
            }
            RTreeAddNodePos(t->rootpos, t->rootlevel, t);
            t->rootpos = n->branch[i].child.pos;
            t->rootlevel--;
            t->n_nodes--;
        }
 
        return 0;
    }
 
    return 1;
}