我正在尝试使用berkeley DB来存储和获取简单的密钥/数据对,但这并不像我所期望的那样工作。
我创建了一个函数(putdb())将一个密钥/数据对放入数据库,并创建了另一个函数(getdb())来检索这一对。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <db.h>
DB *dbp;
void opendb(void)
{
int ret;
if ((ret = db_create(&dbp, NULL, 0)) != 0)
exit(EXIT_FAILURE);
if ((ret = dbp->open(dbp, NULL, "db.db", NULL,DB_BTREE, DB_CREATE, 0664)) != 0)
exit(EXIT_FAILURE);
}
void putdb(const char *key, const char *value)
{
DBT keyValue, dataValue;
memset(&keyValue, 0, sizeof(keyValue));
memset(&dataValue, 0, sizeof(dataValue));
keyValue.size = sizeof(key);
dataValue.size = sizeof(value);
keyValue.data = malloc(keyValue.size);
strcpy(keyValue.data,key);
dataValue.data = malloc(dataValue.size);
strcpy(dataValue.data,value);
if ((ret = dbp->put(dbp, NULL, &keyValue, &dataValue, 0)) == 0)
printf("db: %s: key stored.\n", (char *)keyValue.data);
else {
dbp->err(dbp, ret, "DB->put");
}
dbp->sync(dbp, 0);
}
void getdb(const char *key,const char *value)
{
DBT keyValue, dataValue;
memset(&keyValue, 0, sizeof(keyValue));
memset(&dataValue, 0, sizeof(dataValue));
keyValue.size = sizeof(key);
dataValue.size = sizeof(value);
keyValue.data = malloc(keyValue.size);
strcpy(keyValue.data,key);
dataValue.data = malloc(dataValue.size);
strcpy(dataValue.data,value);
if ((ret = dbp->get(dbp, NULL, &keyValue, &dataValue, 0)) == 0)
printf("db: %s: key retrieved: data was %s.\n",
(char *)keyValue.data, (char *)dataValue.data);
else {
dbp->err(dbp, ret, "DB->get");
}
}
void closedb(void)
{
dbp->close(dbp, 0);
//TODO : error code return check
}
以及主文件:
int main()
{
opendb();
putdb("toto","titi");
getdb("toto","titi");
closedb();
}
我得到:
db: toto: key stored.
DB->get: BDB0073 DB_NOTFOUND: No matching key/data pair found
你能解释一下原因吗?
请注意,如果我更改了主要功能:
int main()
{
opendb();
putdb("toto","titi");
closedb();
opendb();
getdb("toto","titi");
closedb();
}
那就行了!:
db: toto: key stored.
db: toto: key retrieved: data was titi.
最佳答案
你从教程中抄得太多了。它们可以使用sizeof("a string")
,但您必须同时在strlen(key)
和putdb
中使用getdb
keyValue.size = strlen(key);
dataValue.size = strlen(value);
关于c - Berkeley DB在不关闭数据库的情况下无法放置然后访问数据,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/39312527/