C/C++ 多嵌套if else代码C语言改进方法

在我们处理业务代码时，时常会写出多层嵌套的if else代码，这样代码肯定是不符合软件规范的，

如下代码：

if( head->playloadlen != 1 ){if( head->packet_type == PERIOD_INSTRUCTION_REQ ){//LOG_DATA(data + sizeof(cdc_packet_head), len - sizeof(cdc_packet_head));ack_rep = can_periodinfo_def(ctx->singal_data, data + sizeof(cdc_packet_head), len - sizeof(cdc_packet_head),&(ctx->udp));sdc_send_ack(ctx,ack_rep);free(ack_rep);}else if(head-> packet_type == COMPLETE_INSTRUCTION_REQ){ack_rep = can_completeinfo_def(ctx->singal_data, data + sizeof(cdc_packet_head), len - sizeof(cdc_packet_head),&(ctx->udp));sdc_send_ack(ctx,ack_rep);free(ack_rep);}else {;}}else  //服务返回ack接受情况{//正确接受数据if( *(data + sizeof(cdc_packet_head)) == 0x00){}//组包失败或接受数据失败，重新传输else if(*(data + sizeof(cdc_packet_head)) == 0x01){}//多次传输后，仍然错误，删除数据else if(*(data + sizeof(cdc_packet_head)) == 0x02)

在上面代码中，有两层if else 嵌套，判断的条件变量和ack号和协议号。

怎样进行代码改进了，这样参照了linux内核中Netfilter NF_HOOK 中的方法，

改进代码：

#include 
#include 
#include #define __CONNECT2(__A, __B)    __A##__B
#define CONNECT2(__A, __B)      __CONNECT2(__A, __B)#define __CONNECT3(__A, __B, __C)    __A##__B##__C
#define CONNECT3(__A, __B, __C)      __CONNECT3(__A, __B, __C)#define VA_NUM_ARGS_IMPL(_1,_2,_3,_4,_5,_6,_7,_8,_9,__N,...) __N
#define VA_NUM_ARGS(...)                                                \VA_NUM_ARGS_IMPL(__VA_ARGS__,9,8,7,6,5,4,3,2,1)typedef enum
{SCRIPT_NEGATION = 0,VEHICLE_STATUS_REQ,VEHICLE_STATUS_REP,PERIOD_INSTRUCTION_ISSUE,PERIOD_INSTRUCTION_REP,TRIGGER_INSTRUCTION_ISSUE,TRIGGER_INSTRUCTION_REP,FULL_INSTRUCTION_ISSUE,FULL_INSTRUCTION_REP,PERIOD_INSTRUCTION_UPLOAD,PERIOD_INSTRUCTION_UPLOADREP,TRIGGER_INSTRUCTION_UPLOAD,TRIGGER_INSTRUCTION_UPLOADREP,FULL_INSTRUCTION_UPLOAD,FULL_INSTRUCTION_UPLOADREP,VEHICLE_MAX_INSTRUCTION
}CSM_type;struct trans_cmd_t_
{CSM_type m_type;int     p_pro;
}VEHICLE_CMD_TO_INDEX[] =
{{SCRIPT_NEGATION,0x0000},{VEHICLE_STATUS_REQ,0x0001},{VEHICLE_STATUS_REP,0x0002},{PERIOD_INSTRUCTION_ISSUE,0x2001},{PERIOD_INSTRUCTION_REP,0x2002},{TRIGGER_INSTRUCTION_ISSUE,0x2011},{TRIGGER_INSTRUCTION_REP,0x2012},{FULL_INSTRUCTION_ISSUE,0x2021},{FULL_INSTRUCTION_REP,0x2022},{PERIOD_INSTRUCTION_UPLOAD,0x9001},{PERIOD_INSTRUCTION_UPLOADREP,0x9002},{TRIGGER_INSTRUCTION_UPLOAD,0x9011},{TRIGGER_INSTRUCTION_UPLOADREP,0x9012},{FULL_INSTRUCTION_UPLOAD,0x9021},{VEHICLE_MAX_INSTRUCTION,0x9022},
};typedef void (*ap_hookfn)(int pri,void* arg);void test1(int c,void *arg)
{printf("test1----%d  %p--\n",c,arg);}void test2(int c,void *arg)
{printf("test2----%d  %p--\n",c,arg);}void test3(int c,void *arg)
{printf("test3----%d  %p--\n",c,arg);}void test4(int c,void *arg)
{printf("test4----%d  %p--\n",c,arg);}struct list_head
{struct list_head * next;
};/********************************************************************************
*Function:vehicle_to_index
*Description:车辆类型转换
*Return： -1：转换失败，其他成功
Param:
*@packettype[in]:协议类型
********************************************************************************/
static CSM_type vehicle_to_index(unsigned short provalue)
{int i = 0;for( i = 0; i < VEHICLE_MAX_INSTRUCTION;i++){if( VEHICLE_CMD_TO_INDEX[i].p_pro == provalue){return i;}}return -1;
}typedef struct ack_and_packet_hook_ops   
{struct list_head list;ap_hookfn m_hook;int m_ackvalue;  
}ack_and_packet_hook_ops;//头部插入，插在头结点之后，
static inline void list_add_head(struct list_head *new, struct list_head *head) 
{ new->next = head->next;head->next = new;
} ack_and_packet_hook_ops* init_hook_ops(void)
{ack_and_packet_hook_ops *hook_ops = (ack_and_packet_hook_ops*)malloc(sizeof(ack_and_packet_hook_ops) * VEHICLE_MAX_INSTRUCTION);memset(hook_ops,0x00,sizeof(ack_and_packet_hook_ops)*VEHICLE_MAX_INSTRUCTION);  int i = 0;for( i = 0; i < VEHICLE_MAX_INSTRUCTION;i++){hook_ops[i].list.next = &(hook_ops[i].list);}return hook_ops;
}int register_hook_ops4(ack_and_packet_hook_ops* ops,unsigned short provalue,unsigned char ackvalue,ap_hookfn hook)
{int trans_pro_value = vehicle_to_index(provalue);  ack_and_packet_hook_ops* new_class = (ack_and_packet_hook_ops*)calloc(1,sizeof(ack_and_packet_hook_ops));printf("new calloc %p\n",new_class);printf("new calloc %p\n",&new_class->list);new_class->m_ackvalue = ackvalue;new_class->m_hook =  hook;list_add_head(&(new_class->list), &(ops[trans_pro_value].list));return 0;
}int register_hook_ops3(ack_and_packet_hook_ops* ops,unsigned short provalue,ap_hookfn hook)
{int trans_pro_value = vehicle_to_index(provalue); printf("trans_pro_value is %d\n",trans_pro_value);ops[trans_pro_value].m_hook = hook;return 0;
}#define register_hook_ops(...)                           \CONNECT2(register_hook_ops, VA_NUM_ARGS(__VA_ARGS__))    \(__VA_ARGS__) int cdc_hook_thresh(ack_and_packet_hook_ops* ops,unsigned short pro,int ack,int arg1,void* arg2)
{unsigned short actpro = vehicle_to_index(pro);if(ack >= 0){ack_and_packet_hook_ops*  tmp = &(ops[actpro]);while(tmp->list.next != &(tmp->list)){ack_and_packet_hook_ops*l_tmp  = (ack_and_packet_hook_ops*)tmp->list.next;if(l_tmp->m_ackvalue == ack){if(l_tmp->m_hook){l_tmp->m_hook(arg1,arg2);}}printf("&&&&&&&&&&&&&&&&&\n");tmp->list.next =  tmp->list.next->next;}}else{printf("cdc_hook_thresh %d\n",actpro);ops[actpro].m_hook(1,NULL);}}void deinit_hook_ops(ack_and_packet_hook_ops* ops)
{int i = 0;for( i = 0; i < VEHICLE_MAX_INSTRUCTION;i++){ack_and_packet_hook_ops*  tmp = 0;printf("----------------%d----------\n",i);while( ops[i].list.next !=  &(ops[i].list)){printf("----------------%d----------\n",i); tmp = (ack_and_packet_hook_ops*)ops[i].list.next;printf("*********%d***%p**\n",i,ops[i].list.next);  ops[i].list.next = ops[i].list.next->next;free(tmp);  }   }free(ops);return ;
}#define CDC_HOOK_THRESH(ops,pro,ack,arg1,arg2)     cdc_hook_thresh(ops,pro,ack,arg1,arg2); int main(int argc,char* argv[])
{// 测试方法ack_and_packet_hook_ops* test = (ack_and_packet_hook_ops*)calloc(1,sizeof(ack_and_packet_hook_ops));printf("%p---%p\n",test,&(test->list));ack_and_packet_hook_ops* ps = init_hook_ops();/*登记服务器返回协议ACK处理函数*/    register_hook_ops(ps,0x2001,0x00,test1);    register_hook_ops(ps,0x2001,0x01,test2);register_hook_ops(ps,0x2002,0x00,test1);    register_hook_ops(ps,0x2002,0x01,test2);/*登记处理服务器下发的协议*/register_hook_ops(ps,0x2012,test3);char p[] = "hello world";printf("%p\n",p);//CDC_HOOK_THRESH(ps,0x2002,0x00,1,p);//CDC_HOOK_THRESH(ps,0x2012,-1,1,p);deinit_hook_ops(ps);return 0;    
}

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