【编程好习惯】引入中间变量使程序更易读

今天查看自己为《专业嵌入式软件开发》一书所写的代码时发现，个别函数由于没有引入中间变量，使代码行既长又不易读。重构前后的代码如下所示。

重构前：

1. if (TIMER_STARTED == _handle->state_) {
2.    timer_handle_t next;
3. if (g_timer_next == _handle) {
4.        g_timer_next = (timer_handle_t) dll_next (&g_bucket_firing->dll_,  
5.            &_handle->node_);
6.    }
7.    next = (timer_handle_t)dll_next  
8.        (& g_buckets [_handle->bucket_index_].dll_, &_handle->node_);
9. if (0 != next) {
10.        next->round_ += _handle->round_;
11.    }
12.    dll_remove (& g_buckets [_handle->bucket_index_].dll_, &_handle->node_);
13. if ( g_buckets [_handle->bucket_index_].reentrance_ > 0) {
14.        g_bucket_firing->level_ ++;
15.    }
16. }

重构后：

1. if (TIMER_STARTED == _handle->state_) {
2.    timer_handle_t next;
3. bucket_t *p_bucket = &g_buckets [_handle->bucket_index_];
4. if (g_timer_next == _handle) {
5.        g_timer_next = (timer_handle_t) dll_next (&g_bucket_firing->dll_,  
6.            &_handle->node_);
7.    }
8.    next = (timer_handle_t)dll_next (& p_bucket->dll_, &_handle->node_);
9. if (0 != next) {
10.        next->round_ += _handle->round_;
11.    }
12.    dll_remove (& p_bucket->dll_, &_handle->node_);
13. if ( p_bucket->reentrance_ > 0) {
14.        g_bucket_firing->level_ ++;
15.    }
16. }