cbkeyfir.cpp

来自「CBASE v1.01 采用Borland公司TC++编写的数据库管理源程序库」· C++ 代码 · 共 133 行

/*	Copyright (c) 1989 Citadel	*/
/*	   All Rights Reserved    	*/

/* #ident	"@(#)cbkeyfir.c	1.4 - 90/06/20" */

/* ansi headers */
#include <errno.h>
/*#include <stdlib.h>*/
/*#include <string.h>*/

/* library headers */
#include "blkio.h"
#include "btree.h"
#include "lseq.h"

/* local headers */
#include "cbase_.h"

/*man---------------------------------------------------------------------------
NAME
     cbkeyfirst - first cbase key

SYNOPSIS
     #include <cbase.h>

     int cbkeyfirst(cbp, field)
     cbase_t *cbp;
     int field;

DESCRIPTION
     The cbkeyfirst function positions the key cursor of the specified
     field in cbase cbp to the first key.  The record cursor of cbp is
     positioned to the record associated with that key.  Other key
     cursors are not affected.

     cbkeyfirst will fail if one or more of the following is true:

     [EINVAL]       cbp is not a valid cbase pointer.
     [EINVAL]       field is not a valid field number for
                    cbase cbp.
     [CBELOCK]      cbp is not locked.
     [CBENKEY]      field is not a key.
     [CBENOPEN]     cbp is not open.
     [CBENREC]      cbp is empty.

SEE ALSO
     cbkeylast, cbkeynext, cbkeyprev, cbreccnt, cbrecfirst.

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 cbkeyfirst(cbase_t *cbp, int field)
{
	void *buf = NULL;
	cbrpos_t cbrpos = NIL;
	lspos_t lspos = NIL;

	/* validate arguments */
	if (!cb_valid(cbp)) {
		errno = EINVAL;
		return -1;
	}

	/* check if not open */
	if (!(cbp->flags & CBOPEN)) {
		errno = CBENOPEN;
		return -1;
	}

	/* validate arguments */
	if (field < 0 || field >= cbp->fldc) {
		errno = EINVAL;
		return -1;
	}

	/* check if field not a key */
	if (!(cbp->fldv[field].flags & CB_FKEY)) {
		errno = CBENKEY;
		return -1;
	}

	/* check if not locked */
	if (!(cbp->flags & CBLOCKS)) {
		errno = CBELOCK;
		return -1;
	}

	/* check if cbase empty */
	if (lsreccnt(cbp->lsp) == 0) {
		errno = CBENREC;
		return -1;
	}

	/* set key cursor to first key */
	if (btfirst(cbp->btpv[field]) == -1) {
		CBEPRINT;
		return -1;
	}

	/* get record position */
	if (btkeysize(cbp->btpv[field]) != (cbp->fldv[field].len + sizeof(cbrpos_t))) {
		CBEPRINT;
		errno = CBEPANIC;
		return -1;
	}
	buf = calloc((size_t)1, btkeysize(cbp->btpv[field]));
	if (buf == NULL) {
		CBEPRINT;
		errno = ENOMEM;
		return -1;
	}
	if (btgetk(cbp->btpv[field], buf) == -1) {
		CBEPRINT;
		free(buf);
		return -1;
	}
	memcpy(&cbrpos, ((char *)buf + cbp->fldv[field].len), sizeof(cbrpos));
	free(buf);
	buf = NULL;

	/* set record cursor */
	lspos = cbrpos;
	if (lssetcur(cbp->lsp, &lspos) == -1) {
		CBEPRINT;
		return -1;
	}

	errno = 0;
	return 0;
}