Dbxpkey()

PURPOSE

read previous key in active tag

SYNOPSIS

#include "dbl.h"
 
	int	dbxpkey(dbx, key, recno)
 
	<input parameters>
	char	*dbx;		/* Tagged index file descriptor */
 
	<output parameters>
	char	*key;		/* Address of a buffer where the key is returned */
	long	*recno;		/* Address of a buffer where the record  number is returned */

RETURN VALUE

The dbxpkey() function returns 0 for success, or < 0 if an error occurs. See the section on return code values for a detailed list of return codes.

DESCRIPTION

The dbxpkey() function locates the key in descending order in the active tag for the .DBX file. The key and record number is returned.

EXAMPLE

The following example opens the table and tag index, goes to the bottom of the index, reads the previous key by position then by key, rewinds the index, reads the next 6 records in the index, reads the next record by key and then closes the files.

#include <stdio.h>
#include "dbl.h"			/* Recital/Library include file */
#include "dblproto.h"		/* Recital/Library prototype file */
 
	static	dBFIELD fields[6] = {
		"VESSEL",	'C',	18,	0,	0,
		"LAT",	'N',	4,	1,	0,
		"LONG",	'N',	4,	1,	0,
		"AMOUNT",	'N',	10,	0,	0,
		"DATE",	'D',	8,	0,	0,
		"FLAG",	'C',	9,	0,	0
	};
 
	static void errorproc(
		char	*func,
		char	*str,
		int	rc);
 
	main()
	{
		int	rc; 				/* Return Code for error handling */
		char	*dbf; 			/* File descriptor for table */
		char	*dbx; 			/* File descriptor for tagged index */
		int	i;	 			/* Loop control variable */
		char	record[58]; 		/* Array of char for records */
		char	nextkey[10][20]; 	/* Key buffers */
		char	status; 			/* Deleted record flag */
		long	rec_no[10]; 		/* Record number array */
 
		rc = dbdcache(100);
		errorproc("dbdcache()","table cache specified.", rc);
		rc = dbicache(100);
		errorproc("dbicache()", "index cache specified.", rc);
		rc = dbfilemode(1,0);
		rc = dbopen("shipwreck.dbf", &dbf);
		errorproc("dbopen()","table opened in shared mode.", rc);
		rc = dbxopen(dbf, "shipwreck.dbx", &dbx);
		errorproc("dbxopen()","tagged index opened.", rc);
 
		rc = dbxfwd(dbx);
		errorproc("dbxfwd()", "index pointer placed at bottom.", rc);
 
		rc = dbxpkey(dbx, nextkey[0], rec_no);
		errorproc("dbxpkey()", "previous key found in tagged index.", rc);
		printf("\t\tprev key: \t%s\n", nextkey[0]);
 
		rc = dbxgetpr(dbf, dbx, record, &status);
		errorproc("dbxgetpr()", "previous record (by key) retrieved.", rc);
		printf("Previous: \t%s\n", record);
 
		rc = dbxrewind(dbx);
		errorproc("dbxrewind()", "Tagged index rewound.", rc);
 
		for( i = 1; i <= 6; i++)  {
			rc = dbxgetnr(dbf, dbx, record, &status);
			printf("\t\t%d: %s\n", i,record);
		}
		errorproc("dbxgetnr()", "6 records retrieved by tag key.", rc);
 
		rc = dbxnkey(dbx, nextkey[0], rec_no);
		errorproc("dbxnkey()", "next key retrieved in tagged index.", rc);
		printf("\t\tnext key: \t%s\n", nextkey[0]);
 
		rc = dbxclose(dbx);
			errorproc("dbxclose()", "tagged index closed.", rc);
		rc = dbclose(dbf);
		errorproc("dbclose()", "table closed.", rc);
 
		exit(0);
	}
 
	static void errorproc(func, str, rc)
	char	*func;
	char	*str;
	int	rc;
	{
		if ( rc != SUCCESS ) {
			printf("\n  Error performing function %s -> %d\n", func, rc);
			exit(1);
	}
	printf("Function: \t%s, \t%s - Ok\n", func, str);
	return;
}

SEE ALSO

dbxfwd(), dbxgetnr(), dbxgetpr(), dbxnkey(), dbxrewind()