/*
 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
 * the AT&T man page says.
 *
 * The node_t structure is for internal use only, lint doesn't grok it.
 *
 * Written by reading the System V Interface Definition, not the code.
 *
 * Totally public domain.
 *
 * $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
 * $NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp $
 * $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
 * $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
 */

#include <config.h>
#include "roken.h"
#include "search.h"
#include <stdlib.h>

typedef struct node {
  char         *key;
  struct node  *llink, *rlink;
} node_t;

#ifndef __DECONST
#define __DECONST(type, var)    ((type)(uintptr_t)(const void *)(var))
#endif

/*
 * find or insert datum into search tree
 *
 * Parameters:
 *      vkey:   key to be located
 *      vrootp: address of tree root
 */

ROKEN_LIB_FUNCTION void *
rk_tsearch(const void *vkey, void **vrootp,
        int (*compar)(const void *, const void *))
{
        node_t *q;
        node_t **rootp = (node_t **)vrootp;

        if (rootp == NULL)
                return NULL;

        while (*rootp != NULL) {        /* Knuth's T1: */
                int r;

                if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
                        return *rootp;          /* we found it! */

                rootp = (r < 0) ?
                    &(*rootp)->llink :          /* T3: follow left branch */
                    &(*rootp)->rlink;           /* T4: follow right branch */
        }

        q = malloc(sizeof(node_t));             /* T5: key not found */
        if (q != 0) {                           /* make new node */
                *rootp = q;                     /* link new node to old */
                /* LINTED const castaway ok */
                q->key = __DECONST(void *, vkey); /* initialize new node */
                q->llink = q->rlink = NULL;
        }
        return q;
}

/*
 * Walk the nodes of a tree
 *
 * Parameters:
 *      root:   Root of the tree to be walked
 */
static void
trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
         int level)
{

        if (root->llink == NULL && root->rlink == NULL)
                (*action)(root, leaf, level);
        else {
                (*action)(root, preorder, level);
                if (root->llink != NULL)
                        trecurse(root->llink, action, level + 1);
                (*action)(root, postorder, level);
                if (root->rlink != NULL)
                        trecurse(root->rlink, action, level + 1);
                (*action)(root, endorder, level);
        }
}

/*
 * Walk the nodes of a tree
 *
 * Parameters:
 *      vroot:  Root of the tree to be walked
 */
ROKEN_LIB_FUNCTION void
rk_twalk(const void *vroot,
      void (*action)(const void *, VISIT, int))
{
        if (vroot != NULL && action != NULL)
                trecurse(vroot, action, 0);
}

/*
 * delete node with given key
 *
 * vkey:   key to be deleted
 * vrootp: address of the root of the tree
 * compar: function to carry out node comparisons
 */
ROKEN_LIB_FUNCTION void *
rk_tdelete(const void * vkey, void ** vrootp,
        int (*compar)(const void *, const void *))
{
        node_t **rootp = (node_t **)vrootp;
        node_t *p, *q, *r;
        int cmp;

        if (rootp == NULL || (p = *rootp) == NULL)
                return NULL;

        while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
                p = *rootp;
                rootp = (cmp < 0) ?
                    &(*rootp)->llink :          /* follow llink branch */
                    &(*rootp)->rlink;           /* follow rlink branch */
                if (*rootp == NULL)
                        return NULL;            /* key not found */
        }
        r = (*rootp)->rlink;                    /* D1: */
        if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
                q = r;
        else if (r != NULL) {                   /* Right link is NULL? */
                if (r->llink == NULL) {         /* D2: Find successor */
                        r->llink = q;
                        q = r;
                } else {                        /* D3: Find NULL link */
                        for (q = r->llink; q->llink != NULL; q = r->llink)
                                r = q;
                        r->llink = q->rlink;
                        q->llink = (*rootp)->llink;
                        q->rlink = (*rootp)->rlink;
                }
        }
        free(*rootp);                           /* D4: Free node */
        *rootp = q;                             /* link parent to new node */
        return p;
}

/*
 * find a node, or return 0
 *
 * Parameters:
 *      vkey:   key to be found
 *      vrootp: address of the tree root
 */
ROKEN_LIB_FUNCTION void *
rk_tfind(const void *vkey, void * const *vrootp,
      int (*compar)(const void *, const void *))
{
        node_t **rootp = (node_t **)vrootp;

        if (rootp == NULL)
                return NULL;

        while (*rootp != NULL) {                /* T1: */
                int r;

                if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
                        return *rootp;          /* key found */
                rootp = (r < 0) ?
                    &(*rootp)->llink :          /* T3: follow left branch */
                    &(*rootp)->rlink;           /* T4: follow right branch */
        }
        return NULL;
}