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#define LIB_FULL_NAME "/system/lib/libipod.so"
void (*libipod_exit)(int reason) = NULL;
static void (*libipod_setup)(struct ipod_param *) = NULL;
void (*libipod_log)(const char *fmt, ...) = NULL;
void loadlib()
{
void *handle, * func;
handle = dlopen(LIB_FULL_NAME, RTLD_NOW);
if (handle == NULL) {
ipod_log("Can't load library: %s", dlerror());
goto fail_out;
}
if ((libipod_setup = (void (*)(struct ipod_param *))dlsym(handle, "libipod_setup")) == NULL) {
ipod_log("load 'libipod_setup' error: %s", dlerror());
goto close_handle;
}
if ((libipod_exit = (void (*)(int))dlsym(handle, "exit_ipod")) == NULL) {
ipod_log("exit_ipod error: %s", dlerror());
goto close_handle;
}
// logging into kernel log & /data/misc/ipod_log
if ((libipod_log = (void (*)(const char *, ...))dlsym(handle, "ipod_log")) == NULL) {
ipod_log("libipod_log error: %s", dlerror());
goto close_handle;
}
ipod_log("loadlib success!");
return;
close_handle:
dlclose(handle);
fail_out:
do_shutdown("fail to load libipod", false);
}
int main(int argc, char *argv[])
{
loadlib();
......
if(libipod_setup){
libipod_setup(&ipod_param);
if(ipod_param.fast_reboot)
exit_ipod(EXIT_POWER_UP);
}else{
}
}
在main中，通过loadlib()获取到符号libipod_setup、libipod_exit和libipod_log对应的函数地址，进而使用库libipod.so中定义的函数实现。
为了使程序方便扩展，具备通用性，linux提供了加载和处理动态链接库的系统调用。采用异步事件驱动模型，保证主程序逻辑不变，将各个业务以动态链接库的形式加载进来。
参考资料：
1）http://www.cnblogs.com/Anker/p/3746802.html
2）http://blog.csdn.net/ccskyer/article/details/5733508
3）http://blog.csdn.net/bailyzheng/article/details/17613847
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