1 files changed, 85 insertions, 0 deletions
diff --git a/src/nxt_queue.c b/src/nxt_queue.c
new file mode 100644
index 00000000..c81356db
--- /dev/null
+++ b/src/nxt_queue.c
@@ -0,0 +1,85 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) NGINX, Inc.
+ */
+
+
+#include <nxt_main.h>
+
+
+/*
+ * Find the middle queue element if the queue has odd number of elements,
+ * or the first element of the queue's second part otherwise.
+ */
+
+nxt_queue_link_t *
+nxt_queue_middle(nxt_queue_t *queue)
+{
+    nxt_queue_link_t  *middle, *next;
+
+    middle = nxt_queue_first(queue);
+
+    if (middle == nxt_queue_last(queue)) {
+        return middle;
+    }
+
+    next = middle;
+
+    for ( ;; ) {
+        middle = nxt_queue_next(middle);
+
+        next = nxt_queue_next(next);
+
+        if (next == nxt_queue_last(queue)) {
+            return middle;
+        }
+
+        next = nxt_queue_next(next);
+
+        if (next == nxt_queue_last(queue)) {
+            return middle;
+        }
+    }
+}
+
+
+/*
+ * nxt_queue_sort() provides a stable sort because it uses the insertion
+ * sort algorithm.  Its worst and average computational complexity is O^2.
+ */
+
+void
+nxt_queue_sort(nxt_queue_t *queue,
+    nxt_int_t (*cmp)(const void *data, const nxt_queue_link_t *,
+    const nxt_queue_link_t *), const void *data)
+{
+    nxt_queue_link_t  *link, *prev, *next;
+
+    link = nxt_queue_first(queue);
+
+    if (link == nxt_queue_last(queue)) {
+        return;
+    }
+
+    for (link = nxt_queue_next(link);
+         link != nxt_queue_tail(queue);
+         link = next)
+    {
+        prev = nxt_queue_prev(link);
+        next = nxt_queue_next(link);
+
+        nxt_queue_remove(link);
+
+        do {
+            if (cmp(data, prev, link) <= 0) {
+                break;
+            }
+
+            prev = nxt_queue_prev(prev);
+
+        } while (prev != nxt_queue_head(queue));
+
+        nxt_queue_insert_after(prev, link);
+    }
+}