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BTLAST.C
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1989-08-31
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/* Copyright (c) 1989 Citadel */
/* All Rights Reserved */
/* #ident "btlast.c 1.1 - 89/07/03" */
#include <blkio.h>
#include <errno.h>
#include "btree_.h"
/*man---------------------------------------------------------------------------
NAME
btlast - last btree key
SYNOPSIS
#include <btree.h>
int btlast(btp)
btree_t *btp;
DESCRIPTION
The btlast function positions the cursor of btree btp on the last
key in that btree.
btlast will fail if one or more of the following is true:
[EINVAL] btp is not a valid btree pointer.
[BTELOCK] btp is not locked.
[BTENKEY] btp is empty.
[BTENOPEN] btp is not open.
SEE ALSO
btfirst, btkeycnt, btnext, btprev.
DIAGNOSTICS
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned, and errno set to indicate the error.
------------------------------------------------------------------------------*/
int btlast(btp)
btree_t *btp;
{
int rs = 0;
errno = 0;
/* validate arguments */
if (!bt_valid(btp)) {
errno = EINVAL;
return -1;
}
/* check if not open */
if (!(btp->flags & BTOPEN)) {
errno = BTENOPEN;
return -1;
}
/* check locks */
if (!(btp->flags & BTLOCKS)) {
errno = BTELOCK;
return -1;
}
/* set cursor to last key */
btp->cbtpos.node = btp->bthdr.last;
/* check if tree is empty */
if (btp->cbtpos.node == 0) {
btp->cbtpos.key = 0;
bt_ndinit(btp, btp->cbtnp);
errno = BTENKEY;
return -1;
}
/* read current node */
rs = bt_ndget(btp, btp->cbtpos.node, btp->cbtnp);
if (rs == -1) {
BTEPRINT;
btp->cbtpos.node = 0;
btp->cbtpos.key = 0;
bt_ndinit(btp, btp->cbtnp);
return -1;
}
/* set cursor to last key in node */
btp->cbtpos.key = btp->cbtnp->n;
errno = 0;
return 0;
}