Difference between revisions of "Dbxpkey()"
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<output parameters> | <output parameters> | ||
| − | char *key; /* Address of a buffer where the key | + | char *key; /* Address of a buffer where the key is returned */ |
| − | + | long *recno ; /* Address of a buffer where the record number is returned */ | |
| − | long *recno ; /* Address of a buffer where the record number | + | |
| − | + | ||
</code> | </code> | ||
Revision as of 13:17, 1 April 2009
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("ttprev key: t%sn", nextkey[0]); rc = dbxgetpr(dbf, dbx, record, &status); errorproc("dbxgetpr()", "previous record (by key) retrieved.", rc); printf("Previous: t%sn", record); rc = dbxrewind(dbx); errorproc("dbxrewind()", "Tagged index rewound.", rc); for( i = 1; i <= 6; i++) { rc = dbxgetnr(dbf, dbx, record, &status); printf("tt%d: %sn", 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("ttnext key: t%sn", 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 -> %dn", func, rc); exit(1); } printf("Function: t%s, t%s - Okn", func, str); return; }
