Please explain the codes in each line(very detailed). Trying to understand the logic. queue lab. C lang

/* 

 Reverse elements in queue 

 No effect if q is NULL or empty 

 This function should not allocate or free any list elements 

 (e.g., by calling q_insert_head, q_insert_tail, or q_remove_head). 

 It should rearrange the existing ones. 

 */ 

void q_reverse(queue_t *q) 

{ 

 /* You need to write the code for this function */ 

if(!q || !q->head) 

 return; 

 if(q->n == 1) 

 return; 

 list_ele_t *begin, *last, *next; 

 begin = q->head->next; 

 last = q->head; 

 q->head->next = NULL; 

while(true) 

 { 

 next = begin->next; 

 begin->next = last; 

 last = begin; 

 begin = next; 

 if(begin == NULL) 

 { 

 q->tail = q->head; 

 q->head = last; 

 return; 

 } 

 } 

}