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)，
??? 第一個參數(shù)為你的主調(diào)函數(shù)傳遞過來的指針，
??? 第二個參數(shù)為變量的個數(shù)，
??? 第三個為變量的值，
??? 第四個為變量的名稱，
??? 有兩個問題需要注意：
??????? 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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