The code is implementing a merge function that takes in...

March 29, 2023 at 07:12 AM

static struct list_head *merge(void *priv, list_cmp_func_t cmp, struct list_head *a, struct list_head *b) { struct list_head *head, **tail = &head, **node; do { node = cmp(priv, a, b) <= 0 ? &a : &b; *tail = *node; tail = &(*node)->next; } while ((*node = (*node)->next)); *tail = (struct list_head *) ((uintptr_t) a | (uintptr_t) b); return head;

The code is implementing a merge function that takes in two linked lists (pointers to their heads), a user-defined comparison function cmp, and a private data pointer priv. The function uses the comparison function to compare elements between the two input lists, creates a new list by merging the two lists according to the comparison function, and returns a pointer to the head of the merged list.

The function first declares a pointer to the head of the merged list (head) and a double pointer to the tail node of the merged list (tail), initially pointing to the address of the head pointer.

Then, it enters a do-while loop where it repeatedly compares the elements at the current position in each list using the comparison function (cmp). If the element in list a is less than or equal to the element in list b, the current node in list a is added to the merged list, otherwise the current node in list b is added. The tail pointer is updated to point to the next empty slot in the merged list.

The loop continues until one of the input lists is fully processed (i.e., its node pointer reaches NULL). At this point, the remaining nodes in the other list are appended to the end of the merged list using a bitwise OR operation on their pointers, and the head pointer is returned.

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