Difference between revisions of "Dbxgetpr()"
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<input parameters> | <input parameters> | ||
| − | char *dbf; /* Table file descriptor | + | char *dbf; /* Table file descriptor */ |
| − | char *dbx; | + | char *dbx; /* Tagged index file descriptor */ |
<output parameters> | <output parameters> | ||
| − | char *record; /* Address of a buffer where the record data is returned */ | + | char *record; /* Address of a buffer where the record data is returned */ |
| − | char *status; /* Record status, if marked for deletion = 0, otherwise 1 */ | + | char *status; /* Record status, if marked for deletion = 0, otherwise 1 */ |
</code> | </code> | ||
| Line 28: | Line 28: | ||
==DESCRIPTION== | ==DESCRIPTION== | ||
| − | The dbxgetpr() | + | The dbxgetpr() reads the previous record in descending order in the active tag and returns the record data. |
| Line 40: | Line 40: | ||
<code lang="c"> | <code lang="c"> | ||
#include <stdio.h> | #include <stdio.h> | ||
| − | #include "dbl.h" | + | #include "dbl.h" /* Recital/Library include file */ |
| − | #include "dblproto.h" /* Recital/Library prototype file */ | + | #include "dblproto.h" /* Recital/Library prototype file */ |
static dBFIELD fields[6] = { | static dBFIELD fields[6] = { | ||
| Line 59: | Line 59: | ||
main() | 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); | |
} | } | ||
| Line 116: | Line 116: | ||
{ | { | ||
if ( rc != SUCCESS ) { | if ( rc != SUCCESS ) { | ||
| − | + | printf("\n Error performing function %s -> %d\n", func, rc); | |
| − | + | exit(1); | |
} | } | ||
| − | printf("Function: t%s, t%s - | + | printf("Function: \t%s, \t%s - Ok\n", func, str); |
return; | return; | ||
} | } | ||
Latest revision as of 15:33, 5 May 2009
PURPOSE
get previous data record by key in active tag
SYNOPSIS
#include "dbl.h" int dbxgetpr(dbf, dbx, record, status) <input parameters> char *dbf; /* Table file descriptor */ char *dbx; /* Tagged index file descriptor */ <output parameters> char *record; /* Address of a buffer where the record data is returned */ char *status; /* Record status, if marked for deletion = 0, otherwise 1 */
RETURN VALUE
The dbxgetpr() 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 dbxgetpr() reads the previous record in descending order in the active tag and returns the record data.
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; }
