Linux内核中的bsearch二分查找函数

  

   

    

     

    
    

     

      /*
     
    
   

    

     

    
    

     

      * bsearch - binary search an array of elements
     
    
   

    

     

    
    

     

      * @key: pointer to item being searched for
     
    
   

    

     

    
    

     

      * @base: pointer to first element to search
     
    
   

    

     

    
    

     

      * @num: number of elements
     
    
   

    

     

    
    

     

      * @size: size of each element
     
    
   

    

     

    
    

     

      * @cmp: pointer to comparison function
     
    
   

    

     

    
    

     

      *
     
    
   

    

     

    
    

     

      * This function does a binary search on the given array. The
     
    
   

    

     

    
    

     

      * contents of the array should already be in ascending sorted order
     
    
   

    

     

    
    

     

      * under the provided comparison function.
     
    
   

    

     

    
    

     

      *
     
    
   

    

     

    
    

     

      * Note that the key need not have the same type as the elements in
     
    
   

    

     

    
    

     

      * the array, e.g. key could be a string and the comparison function
     
    
   

    

     

    
    

     

      * could compare the string with the struct's name field. However, if
     
    
   

    

     

    
    

     

      * the key and elements in the array are of the same type, you can use
     
    
   

    

     

    
    

     

      * the same comparison function for both sort() and bsearch().
     
    
   

    

     

    
    

     

      */
     
    
   

    

     

    
    

     

      void *bsearch(const void *key, const void *base, size_t num, size_t size,
     
    
   

    

     

    
    

     
	int(*cmp)(const void *key, const void *elt))
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     
	size_t start = 0, end = num;
     
    
   

    

     

    
    

     
	int result;
     
    
   

    

     

    
    

     
	while (start < end) {
     
    
   

    

     

    
    

     
		size_t mid = start + (end - start) / 2;
     
    
   

    

     

    
    

     

      		result = cmp(key, base + mid * size);
     
    
   

    

     

    
    

     
		if (result < 0)
     
    
   

    

     

    
    

     

      			end = mid;
     
    
   

    

     

    
    

     
		else if (result > 0)
     
    
   

    

     

    
    

     

      			start = mid + 1;
     
    
   

    

     

    
    

     
		else
     
    
   

    

     

    
    

     
			return (void *)base + mid * size;
     
    
   

    

     

    
    

     

      	}
     
    
   

    

     

    
    

     
	return NULL;
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     

      EXPORT_SYMBOL(bsearch);
     
    
  
 

文章来源: blog.csdn.net，作者：csuzhucong，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/nameofcsdn/article/details/78139602