一种环形双向链表的操作

最新推荐文章于 2025-02-10 18:18:44 发布

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最新推荐文章于 2025-02-10 18:18:44 发布

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分类专栏：程序设计文章标签：链表数据结构

本文链接：https://blog.youkuaiyun.com/yueyuanhuaqing/article/details/131328966

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1. 任务需求

在BLE扫描过程中，由于Privacy地址的加入，TIFS的时隙不能满足解析耗时的时间处理，这里将解析和时序ACK分为两个步骤，比如scan_req的ScanA解析和回复SCAN_RSP 两个步骤。

2. 方案设计

这就需要一种链表数据结构记录这两个步骤的动作，不同的设备使用地址和地址类型这两个变量来进行判断，链表作用是可以缓存多个设备并且可以实现有序性。收到设备后该需要进行以下流程：

（1）检查该设备的地址和地址类型是否已经存在，不存在就添加到链表中，（当然前提还需判断该设备是为Privacy地址，进行解析，但是解析失败或者解析成功）；

（2）如果该设备已经存在该链表中，就不需要重复上述动作，就直接执行协议动作回复SCAN_RSP;

3. 环形链表设计

构造一个环形双向结构的链表，当有数据添加时，该链表的头指针顺时针旋转，当需要查询当前列表的选项时需要逆时针旋转查询。将扫描请求按照时间顺序添加到链表中。

对环形链表的操作有三种：

(1) 初始化，这里使用数组；

(2) 添加或者更新链表项；

(3) 环形链表的遍历；

头文件代码：


#define DEVICE_RESOLVED_LIST_ITEM_NUM   (6)
#define DEVICE_RESOLVED_LIST_INVALID_INDEX   0xff
typedef enum
{
  RESOLVED_FAILED_LEGACY_ADV_LIST = 0,
  RESOLVED_FAILED_LEGACY_SCAN_LIST = 1,
  RESOLVED_FAILED_LEGACY_INIT_LIST = 2,
  RESOLVED_FAILED_EXTEND_ADV_LIST = 3,
  RESOLVED_FAILED_EXTEND_SCAN_LIST = 4,   //unused
  RESOLVED_FAILED_EXTEND_INIT_LIST = 5,   //unused
  RESOLVED_FAILED_LIST_NUM = 6,
}resolved_failed_list_index;

typedef struct resolved_failed_info {
  u_int8        device_type;
  u_int8        device_addr[BD_ADDR_LEN];
  struct resolved_failed_info *  p_next;
  struct resolved_failed_info *  p_prev;
}Reloved_Failed_Device_Info;

源文件代码


W1_BT_DATA_PATCH Reloved_Failed_Device_Info g_resolved_failed_list[DEVICE_RESOLVED_LIST_ITEM_NUM * RESOLVED_FAILED_LIST_NUM] = { 0 };
W1_BT_DATA_PATCH Reloved_Failed_Device_Info *g_resolved_failed_list_head_arr[RESOLVED_FAILED_LIST_NUM] = { 0 };

Reloved_Failed_Device_Info *aml_device_resolved_failed_list_check_item_exist(resolved_failed_list_index list_index, u_int8 device_type, u_int8 *p_addr)
{
  if (device_type != RANDOM_DEVICE_ADDRESS_TYPE)
    return NULL;
  if (p_addr == NULL)
  {
    return NULL;
  }
  if (list_index >= RESOLVED_FAILED_LIST_NUM)
    return NULL;
  Reloved_Failed_Device_Info *p_list_head = g_resolved_failed_list_head_arr[list_index];
  if (p_list_head == NULL)
  {
    return NULL;
  }
  Reloved_Failed_Device_Info *p_temp = p_list_head;
  for (; (p_temp != NULL); p_temp = p_temp->p_next)
  {
    if ((aml_addr_is_equal(p_temp->device_addr, p_addr))
        && (p_temp->device_type == device_type))
    {
      return p_temp;
    }

    if (p_temp == p_list_head->p_prev)
    {
      break;
    }
  }
  return NULL;
}

Reloved_Failed_Device_Info *aml_device_resolved_failed_list_get_idle_item(resolved_failed_list_index list_index)
{
  if (list_index >= RESOLVED_FAILED_LIST_NUM)
    return NULL;

  Reloved_Failed_Device_Info *p_list_head = g_resolved_failed_list_head_arr[list_index];

  if (p_list_head == NULL)
  {
    //init the buffer
    p_list_head = &g_resolved_failed_list[list_index * DEVICE_RESOLVED_LIST_ITEM_NUM];

    for (u_int8 index = 0; index < DEVICE_RESOLVED_LIST_ITEM_NUM; index++)
    {
      Reloved_Failed_Device_Info *p_temp = p_list_head + index;

      p_temp->p_next = &p_list_head[(index + 1) % DEVICE_RESOLVED_LIST_ITEM_NUM];
      p_temp->p_prev = &p_list_head[(index + DEVICE_RESOLVED_LIST_ITEM_NUM - 1) % DEVICE_RESOLVED_LIST_ITEM_NUM];
    }

    g_resolved_failed_list_head_arr[list_index] = p_list_head;
    return p_list_head;
  }

  return p_list_head->p_prev;
}

Reloved_Failed_Device_Info *aml_device_resolved_failed_list_add_item(resolved_failed_list_index list_index, u_int8 device_type, u_int8 *p_addr)
{
  Reloved_Failed_Device_Info *p_idle_item = NULL;

  if (device_type != RANDOM_DEVICE_ADDRESS_TYPE)
    return NULL;

  if (p_addr == NULL)
  {
    return NULL;
  }

  if (list_index >= RESOLVED_FAILED_LIST_NUM)
  {
    return NULL;
  }

  p_idle_item = aml_device_resolved_failed_list_get_idle_item(list_index);//aml_device_resolved_failed_list_check_item_exist(device_type, p_addr);
  if (p_idle_item == NULL)
  {
    return NULL;
  }

  {
    p_idle_item->device_type = device_type;
    aml_copy_array(BD_ADDR_LEN, p_idle_item->device_addr, p_addr);
  }

  g_resolved_failed_list_head_arr[list_index] = p_idle_item;
  //p_resolved_failed_list_head = p_idle_item;
  return p_idle_item;
}

Reloved_Failed_Device_Info *aml_device_resolved_failed_list_update_item(resolved_failed_list_index list_index, Reloved_Failed_Device_Info *p_new_item)
{
  if (p_new_item == NULL)
  {
    return NULL;
  }
  if (list_index >= RESOLVED_FAILED_LIST_NUM)
  {
    return NULL;
  }
  Reloved_Failed_Device_Info *p_list_head = g_resolved_failed_list_head_arr[list_index];
  if (p_list_head == p_new_item)
  {
    //nothing to be done
  }
  else if (p_list_head == p_new_item->p_prev)
  {
    //p_head_item just move to next item
    p_list_head = p_new_item;
  }
  else
  {
    //update the list
    //pick up out the list
    p_new_item->p_next->p_prev = p_new_item->p_prev;
    p_new_item->p_prev->p_next = p_new_item->p_next;

    //insert the item into the list
    p_new_item->p_prev = p_list_head->p_prev;
    p_new_item->p_next = p_list_head;

    p_list_head->p_prev->p_next = p_new_item;
    p_list_head->p_prev = p_new_item;
  }

  g_resolved_failed_list_head_arr[list_index] = p_new_item;
  //p_resolved_failed_list_head = p_idle_item;
  return p_new_item;
}