Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 96 insertions, 0 deletions

diff --git a/prio-queue.c b/prio-queue.c
new file mode 100644
index 000000000000..d3f488cb05f2
--- /dev/null
+++ b/prio-queue.c
@@ -0,0 +1,96 @@
+#include "cache.h"
+#include "prio-queue.h"
+
+static inline int compare(struct prio_queue *queue, int i, int j)
+{
+	int cmp = queue->compare(queue->array[i].data, queue->array[j].data,
+				 queue->cb_data);
+	if (!cmp)
+		cmp = queue->array[i].ctr - queue->array[j].ctr;
+	return cmp;
+}
+
+static inline void swap(struct prio_queue *queue, int i, int j)
+{
+	SWAP(queue->array[i], queue->array[j]);
+}
+
+void prio_queue_reverse(struct prio_queue *queue)
+{
+	int i, j;
+
+	if (queue->compare != NULL)
+		BUG("prio_queue_reverse() on non-LIFO queue");
+	for (i = 0; i < (j = (queue->nr - 1) - i); i++)
+		swap(queue, i, j);
+}
+
+void clear_prio_queue(struct prio_queue *queue)
+{
+	FREE_AND_NULL(queue->array);
+	queue->nr = 0;
+	queue->alloc = 0;
+	queue->insertion_ctr = 0;
+}
+
+void prio_queue_put(struct prio_queue *queue, void *thing)
+{
+	int ix, parent;
+
+	/* Append at the end */
+	ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
+	queue->array[queue->nr].ctr = queue->insertion_ctr++;
+	queue->array[queue->nr].data = thing;
+	queue->nr++;
+	if (!queue->compare)
+		return; /* LIFO */
+
+	/* Bubble up the new one */
+	for (ix = queue->nr - 1; ix; ix = parent) {
+		parent = (ix - 1) / 2;
+		if (compare(queue, parent, ix) <= 0)
+			break;
+
+		swap(queue, parent, ix);
+	}
+}
+
+void *prio_queue_get(struct prio_queue *queue)
+{
+	void *result;
+	int ix, child;
+
+	if (!queue->nr)
+		return NULL;
+	if (!queue->compare)
+		return queue->array[--queue->nr].data; /* LIFO */
+
+	result = queue->array[0].data;
+	if (!--queue->nr)
+		return result;
+
+	queue->array[0] = queue->array[queue->nr];
+
+	/* Push down the one at the root */
+	for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
+		child = ix * 2 + 1; /* left */
+		if (child + 1 < queue->nr &&
+		    compare(queue, child, child + 1) >= 0)
+			child++; /* use right child */
+
+		if (compare(queue, ix, child) <= 0)
+			break;
+
+		swap(queue, child, ix);
+	}
+	return result;
+}
+
+void *prio_queue_peek(struct prio_queue *queue)
+{
+	if (!queue->nr)
+		return NULL;
+	if (!queue->compare)
+		return queue->array[queue->nr - 1].data;
+	return queue->array[0].data;
+}