diff --git a/auto/sources b/auto/sources
index ed78c71..62fb047 100644
--- a/auto/sources
+++ b/auto/sources
@@ -44,6 +44,7 @@
            src/core/ngx_list.c \
            src/core/ngx_hash.c \
            src/core/ngx_buf.c \
+           src/core/ngx_queue.c \
            src/core/ngx_output_chain.c \
            src/core/ngx_string.c \
            src/core/ngx_parse.c \
diff --git a/src/core/ngx_queue.c b/src/core/ngx_queue.c
new file mode 100644
index 0000000..a49b5c6
--- /dev/null
+++ b/src/core/ngx_queue.c
@@ -0,0 +1,79 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.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
+ */
+
+ngx_queue_t *
+ngx_queue_middle(ngx_queue_t *queue)
+{
+    ngx_queue_t  *middle, *next;
+
+    middle = ngx_queue_head(queue);
+
+    if (middle == ngx_queue_last(queue)) {
+        return middle;
+    }
+
+    next = ngx_queue_head(queue);
+
+    for ( ;; ) {
+        middle = ngx_queue_next(middle);
+
+        next = ngx_queue_next(next);
+
+        if (next == ngx_queue_last(queue)) {
+            return middle;
+        }
+
+        next = ngx_queue_next(next);
+
+        if (next == ngx_queue_last(queue)) {
+            return middle;
+        }
+    }
+}
+
+
+/* the stable insertion sort */
+
+void
+ngx_queue_sort(ngx_queue_t *queue,
+    ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *))
+{
+    ngx_queue_t  *q, *prev, *next;
+
+    q = ngx_queue_head(queue);
+
+    if (q == ngx_queue_last(queue)) {
+        return;
+    }
+
+    for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) {
+
+        prev = ngx_queue_prev(q);
+        next = ngx_queue_next(q);
+
+        ngx_queue_remove(q);
+
+        do {
+            if (cmp(prev, q) <= 0) {
+                break;
+            }
+
+            prev = ngx_queue_prev(prev);
+
+        } while (prev != ngx_queue_sentinel(queue));
+
+        ngx_queue_insert_after(prev, q);
+    }
+}
diff --git a/src/core/ngx_queue.h b/src/core/ngx_queue.h
index 1407d85..9a1763d 100644
--- a/src/core/ngx_queue.h
+++ b/src/core/ngx_queue.h
@@ -36,6 +36,16 @@
     (h)->next = x
 
 
+#define ngx_queue_insert_after   ngx_queue_insert_head
+
+
+#define ngx_queue_insert_tail(h, x)                                           \
+    (x)->prev = (h)->prev;                                                    \
+    (x)->prev->next = x;                                                      \
+    (x)->next = h;                                                            \
+    (h)->prev = x
+
+
 #define ngx_queue_head(h)                                                     \
     (h)->next
 
@@ -44,6 +54,18 @@
     (h)->prev
 
 
+#define ngx_queue_sentinel(h)                                                 \
+    (h)
+
+
+#define ngx_queue_next(q)                                                     \
+    (q)->next
+
+
+#define ngx_queue_prev(q)                                                     \
+    (q)->prev
+
+
 #if (NGX_DEBUG)
 
 #define ngx_queue_remove(x)                                                   \
@@ -61,8 +83,29 @@
 #endif
 
 
+#define ngx_queue_split(h, q, n)                                              \
+    (n)->prev = (h)->prev;                                                    \
+    (n)->prev->next = n;                                                      \
+    (n)->next = q;                                                            \
+    (h)->prev = (q)->prev;                                                    \
+    (h)->prev->next = h;                                                      \
+    (q)->prev = n;
+
+
+#define ngx_queue_add(h, n)                                                   \
+    (h)->prev->next = (n)->next;                                              \
+    (n)->next->prev = (h)->prev;                                              \
+    (h)->prev = (n)->prev;                                                    \
+    (h)->prev->next = h;
+
+
 #define ngx_queue_data(q, type, link)                                         \
     (type *) ((u_char *) q - offsetof(type, link))
 
 
+ngx_queue_t *ngx_queue_middle(ngx_queue_t *queue);
+void ngx_queue_sort(ngx_queue_t *queue,
+    ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *));
+
+
 #endif /* _NGX_QUEUE_H_INCLUDED_ */