new ngx_queue functions

1 files changed, 79 insertions, 0 deletions

diff --git a/src/core/ngx_queue.c b/src/core/ngx_queue.c
new file mode 100644
index 000000000..a49b5c663
--- /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);
+    }
+}