tools/lib/list_sort.c

129  * 2:1 balanced merges.  Given two pending sublists of size 2^k, they are
139  * pending lists.  This is beautifully simple code, but rather subtle.
147  * 2^k, which is when we have 2^k elements pending in smaller lists,
152  * a third list of size 2^(k+1), so there are never more than two pending.
154  * The number of pending lists of size 2^k is determined by the
163  * 0:  00x: 0 pending of size 2^k;           x pending of sizes < 2^k
164  * 1:  01x: 0 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
165  * 2: x10x: 0 pending of size 2^k; 2^k     + x pending of sizes < 2^k
166  * 3: x11x: 1 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
167  * 4: y00x: 1 pending of size 2^k; 2^k     + x pending of sizes < 2^k
168  * 5: y01x: 2 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
177  * When we reach the end of the input, we merge all the pending
186 	struct list_head *list = head->next, *pending = NULL;
187 	size_t count = 0;	/* Count of pending */
199 	 * - pending is a prev-linked "list of lists" of sorted
204 	 * - A pair of pending sublists are merged as soon as the number
205 	 *   of following pending elements equals their size (i.e.
215 		struct list_head **tail = &pending;
230 		/* Move one element from input list to pending */
231 		list->prev = pending;
232 		pending = list;
234 		pending->next = NULL;
238 	/* End of input; merge together all the pending lists. */
239 	list = pending;
240 	pending = pending->prev;
242 		struct list_head *next = pending->prev;
246 		list = merge(priv, cmp, pending, list);
247 		pending = next;
250 	merge_final(priv, cmp, head, pending, list);