db.c.svn-base

一个berkerly db数据库的演示DEMO

#include <db.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define	DATABASE "demo.db"

void _read(DB *dbp, int n);
void _write(DB *dbp, int n);
void _all(DB *dbp, int n);
void _delete(DB *dbp, int n);

typedef struct {
  int id;
  int mt_id;
  float in, out;
} DATA, *PDATA;


/* 以下程序代码的程序头同此 */
int main(int argc, char *argv[])
{	DB *dbp;
	int ret;

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

	if (argc != 3)
	{
		printf("Usage: %s [rwda] n\n", argv[0]);
		exit(0);
	}

	if (argv[1][0] == 'r')
		_read(dbp, atoi(argv[2]));
	else if (argv[1][0] == 'w')
	{
		int n = atoi(argv[2]);
		while(n--)
			_write(dbp, n);
	}
	else if (argv[1][0] == 'a') //print all
	{
		_all(dbp, atoi(argv[2]));
		_all(dbp, atoi(argv[2]));
	}
	else if (argv[1][0] == 'd')
		_delete(dbp, atoi(argv[2]));

	dbp->close(dbp, 0);
	return 0;
}

void _read(DB *dbp, int n)
{
	DBT key, data;
	DATA *d;
	
	memset(&key, 0, sizeof(key));
	memset(&data, 0, sizeof(data));

	int a = n;
	key.data = &a;
	key.size = sizeof(int);
	dbp->get(dbp, NULL, &key, &data, 0);
	d = data.data;
	if (d == NULL)
	{
		printf("No record.\n");
		return;
	}
	printf("db read: key=%d, id=%d, mt_id=%d, in=%f, out=%f\n", 
			*((int *)key.data),
			d->id, d->mt_id, d->in, d->out);
}

void _write(DB *dbp, int n)
{
	DBT key, data;
	int ret;
	DATA *d = (DATA *)malloc(sizeof(DATA));
	d->id = n; d->mt_id = 14 * n; d->in = 5.20 * n; d->out = 3.71 * n;
	
	memset(&key, 0, sizeof(key));
	memset(&data, 0, sizeof(data));
	key.data = &(n);
	key.size = sizeof(int);
	data.data = d;
	data.size = sizeof(DATA);
	if ((ret = dbp->put(dbp, NULL, &key, &data, DB_APPEND)) == 0)
		printf("db: %d: key stored.\n", *((int *)key.data));
	else
		dbp->err(dbp, ret, "DB->put");
	free(d);
}

void _all(DB *dbp, int n)
{
	DBT key, data;
	int ret;
	DBC * cur;
	DATA *d;
	int i = 0;
	
	memset(&key, 0, sizeof(key));
	memset(&data, 0, sizeof(data));

    dbp->cursor(dbp, NULL, &cur, 0);
    while((ret = cur->c_get(cur, &key, &data, DB_NEXT)) == 0)
    {
	d = data.data;
	int key_id = *((int *)key.data);
	printf("db read: key=%d, id=%d, mt_id=%d, in=%f, out=%f\n", 
			key_id,
			d->id, d->mt_id, d->in, d->out);
	if (key_id % 2 == 0)
	{
		printf("del key=%d\n", key_id);
		cur->c_del(cur, 0);
	}
	i++;
	if (i >= n)
	{
		printf ("max reached.\n");
		return;
	}
    }
    cur->c_close(cur);
}

void _delete(DB *dbp, int n)
{
	DBT key, data;
	
	memset(&key, 0, sizeof(key));
	memset(&data, 0, sizeof(data));

	int a = n;
	key.data = &a;
	key.size = sizeof(int);
	dbp->del(dbp, NULL, &key, 0);
	printf("db del: key=%d\n", *((int *)key.data));
}