#include<stdio.h>
#include<stdlib.h>
#define N  20

typedef struct buf_t buf;
struct buf_t
{
      int                 buftId;                    
         
      buf     *prev;
      buf     *next;

};

typedef struct Data_t Data;



struct Data_t
{
   
    buf *busyList;
};

Data  gData;

buf  bufs[N];

void AddtoHead(buf **headerPPtr,
                                   buf *newPtr)
{

       if (*headerPPtr != NULL)
    {
          newPtr->prev = (*headerPPtr)->prev;
        newPtr->next = *headerPPtr;
        (*headerPPtr)->prev->next = newPtr;
        (*headerPPtr)->prev = newPtr;
    }
    else
    {

        *headerPPtr  = newPtr;
        newPtr->next = newPtr;
        newPtr->prev = newPtr;
    }

    return;
}



void Data_initialize()
{
    int i;
   
       memset((int*)bufs, 0, sizeof(buf_t) *N);

    for (i = 0; i < N; i++)
    {
        bufs[i].bufId = i;      
    }
  
      memset(&gData, 0, sizeof(gData));

    return;
}




int main()
{
      Data_initialize();

      buf *tmpPtr;
      
     int simIndex = 0;
     int i;
       /*add the bufId to the busylist*/
      for( i = 0;i< 20;i++)
      {
              AddtoHead(&(gData.busyList),
                    &buf[i]);
       }
  
       tmpPtr = Data.busyList;
       while(tmpPtr != NULL )
       {
          printf("%d\n",tmpPtr->bufId);
          tmpPtr = tmpPtr ->next;
       }
}

这段程序怎么理解啊？
先初始化，然后把buf的内容加到gData去？从打印来看，好像是从0,1,2******19循环打印的。

这是双项链表的插入吗？若是的话，那数组一开始就分配好的啊？这样做有什么好处？
而且插入的话应该都是插在表头才对啊，应该是19,18,17,****0？