Question

I am trying to develop a database using Berkeley Db in C. I want to have multiple data inside the database and then access them. my code is below:

#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <db.h>

#define DATABASE "access.db"

typedef struct {
    int id;
    char data1[20];
    char src[20];
} pearson_record;

int
main()
{
    pearson_record s;
    char *papa="1.1.1.1";
    char *source="papa";
    DB *dbp;
    DBT key, data;
    int ret, t_ret;

    if ((ret = db_create(&dbp, NULL, 0)) != 0) {
        fprintf(stderr, "db_create: %s\n", db_strerror(ret));
        exit (1);
    }
    if ((ret = dbp->open(dbp, NULL, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
        dbp->err(dbp, ret, "%s", DATABASE);
        goto err;
    }

    s.id = 10;

    strncpy(s.data1, papa, strlen(papa)+1);
    strncpy(s.src, source, strlen(source)+1);

    memset(&key, 0, sizeof(key));
    memset(&data, 0, sizeof(data));
    //memset(&s, 0, sizeof(struct pearson_record));
    key.data = &(s.id);
    key.size = sizeof(int);
    data.data = &s;
    data.size = sizeof(s);

    papa="1.1.1.2";
    source="papaa";
    strncpy(s.data1, papa, strlen(papa)+1);
    strncpy(s.src, source, strlen(source)+1);

    if ((ret = dbp->put(dbp, NULL, &key,&data,DB_NOOVERWRITE)) == 0)
        printf("db: %d: key stored.\n", *(int *)key.data);
    else
    {
        dbp->err(dbp, ret, "DB->put");
        goto err;
    }
    s.id = 11;

    strncpy(s.data1, papa, strlen(papa)+1);
    strncpy(s.src, source, strlen(source)+1);

    memset(&key, 0, sizeof(key));
    memset(&data, 0, sizeof(data));
    //memset(&s, 0, sizeof(struct pearson_record));
    key.data = &(s.id);
    key.size = sizeof(int);
    data.data = &s;
    data.size = sizeof(s);

    papa="1.1.1.2";
    source="papaa";
    strncpy(s.data1, papa, strlen(papa)+1);
    strncpy(s.src, source, strlen(source)+1);

    if ((ret = dbp->put(dbp, NULL, &key,&data,DB_NOOVERWRITE)) == 0)
        printf("db: %d: key stored.\n", *(int *)key.data);
    else
    {
        dbp->err(dbp, ret, "DB->put");
        goto err;
    }
    pearson_record *ppr;
    if ((ret = dbp->get(dbp, NULL, &key, &data, DB_MULTIPLE)) == 0) {
        ppr = (pearson_record *) data.data;
        printf("db: %d: key retrieved: data was %s,%s. %d\n",
        *(int *)key.data, ppr->data1,ppr->src, data.size);
    } else {
        dbp->err(dbp, ret, "DB->get");
        goto err;
    }

    if ((ret = dbp->get(dbp, NULL, &key, &data, DB_MULTIPLE)) == 0) {
        ppr = (pearson_record *) data.data;
        printf("db: %d: key retrieved: data was %s,%s. %d\n",
        *(int *)key.data, ppr->data1,ppr->src, data.size);
    } else {
        dbp->err(dbp, ret, "DB->get");
        goto err;
    }

    err:
    if ((t_ret = dbp->close(dbp, 0)) != 0 && ret == 0)
        ret = t_ret; 
    exit(ret);
}

Right now it says DB_DBT_MULTIPLE has to be set. I don’t know how to do that. Previously without the flags i was only getting the last entry. Any kind of help would be appreciated. Thanks in advance

Answer 1

If I’m reading your code correctly, you are calling get twice with the same key, which returns the same data for obvious reasons.

If you want to iterate over the records, you will need to use a Cursor, see Chapter 4 of Getting Started with Berkeley DB for a good reference for same.