關(guān)于sqlite_exec回調(diào)函數(shù)中參數(shù)傳遞的問題

2024-09-07 00:10:05

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上一篇轉(zhuǎn)載的文章中涉及到了如何用C來作回調(diào)函數(shù)讀取或?qū)懭隨QLITE數(shù)據(jù)庫的問題，但其中沒有關(guān)于回調(diào)函數(shù)如何作參數(shù)傳遞的問題，比如想要在你的主調(diào)函數(shù)中獲取該變量，就需要通過調(diào)用sqlite3_exec函數(shù)給回調(diào)函數(shù)傳遞結(jié)構(gòu)體指針，下面我作了一例：

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>

struct olt_info
{
int olt_index;
int onu_on_line;
int ui_port1;
int ui_port2;
int ui_port3;
int ui_port4;
};

int my_callback(void * olt_temp, int argc, char * value[], char * name[])
{
int i;
struct olt_info * pdata = NULL;

pdata = (struct olt_info *)olt_temp;

puts("Here below is the code line:/n");
for (i = 0; i < argc; i )
{
printf("%s == %s/n", name[i], value[i]);
}
puts("Code line over./n");

pdata->olt_index = (int)atoi(value[0]);
pdata->onu_on_line = (int)atoi(value[1]);
pdata->ui_port1 = (int)atoi(value[2]);
pdata->ui_port2 = (int)atoi(value[3]);
pdata->ui_port3 = (int)atoi(value[4]);
pdata->ui_port4 = (int)atoi(value[5]);

return 0;
}

int main(int argc, char * argv[])
{
sqlite3 * olt_db = NULL;
int rc = 0;
int i;
char * err_msg = NULL;
char temp_msg[150];
struct olt_info * olt_temp= (struct olt_info *)malloc(sizeof(struct olt_info));

rc = sqlite3_open("olt.db", &olt_db);
if (rc)
{
fprintf(stderr, "Open database error, %s/n", sqlite3_errmsg(olt_db));
exit(1);
}
else
{
fprintf(stdout, "Open database OK./n");
}

rc = sqlite3_exec(olt_db, "create table olt_tbl(olt_index integer primary key autoincrement, onu_on_line smallint, ui_port1 smallint, ui_port2 smallint, ui_port3 smallint, ui_port4 smallint);", NULL, NULL, &err_msg);

if (rc != SQLITE_OK)
{
fprintf(stderr, "Create table error, %s/n", err_msg);
exit(1);
}
else
{
fprintf(stdout, "Create table OK./n");
}

for (i = 0; i < 6; i )
{
sprintf(temp_msg, "insert into olt_tbl(onu_on_line, ui_port1, ui_port2, ui_port3, ui_port4) values(%d, %d, %d, %d, %d)", i * 16, i, i, i, i);
//rc = sqlite3_exec(olt_db, "insert into olt_tbl(onu_on_line, ui_port1, ui_port2, ui_port3, ui_port4) values(32, 1, 1, 1, 1);", NULL, NULL, &err_msg);
rc = sqlite3_exec(olt_db, temp_msg, NULL, NULL, &err_msg);
}

if (rc != SQLITE_OK)
{
fprintf(stderr, "Insert items failure, %s/n", err_msg);
}
else
{
fprintf(stdout, "Insert items OK./n");
}

rc = sqlite3_exec(olt_db, "select * from olt_tbl where olt_index==4;", my_callback, olt_temp, &err_msg);
if (rc != SQLITE_OK)
{
fprintf(stderr, "Selete from olt_tbl failure, %s/n", err_msg);
exit(1);
}
else
{
fprintf(stdout, "Excute sql OK./n");
}

printf("%d-%d-%d-%d-%d-%d/n", olt_temp->olt_index, olt_temp->onu_on_line,olt_temp->ui_port1,olt_temp->ui_port2,olt_temp->ui_port3,olt_temp->ui_port4);

free(olt_temp);

sqlite3_close(olt_db);
return 0;
}

其中my_callback(void * pdata, int argc, char * value[], char *name[])為回調(diào)函數(shù)，切記回調(diào)函數(shù)只能按照這種格式來定義參數(shù)，
第一個(gè)參數(shù)為你的主調(diào)函數(shù)傳遞過來的指針，
第二個(gè)參數(shù)為變量的個(gè)數(shù)，
第三個(gè)為變量的值，
第四個(gè)為變量的名稱，
有兩個(gè)問題需要注意：
一、這里面參數(shù)都是字符串類型，根據(jù)您的需要作出強(qiáng)制類型轉(zhuǎn)換即可。
二、第一個(gè)參數(shù)為void *類型，需要在你的回調(diào)函數(shù)里強(qiáng)制轉(zhuǎn)換成需要的類型。

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