X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;f=lib%2Flists.h;h=fa9599aa9f8e943b527d9d200ea3e686d3bcb158;hb=2e2adfa5d7ac912434bef5b8a9b25cfb14d4a4a6;hp=0c0ab0f6069b6c57c01832626ae4559c93c07579;hpb=1571781022499a9d0c32d249f89945d034d1cbff;p=libucw.git

diff --git a/lib/lists.h b/lib/lists.h
index 0c0ab0f6..fa9599aa 100644
--- a/lib/lists.h
+++ b/lib/lists.h
@@ -7,6 +7,19 @@
 #ifndef _SHERLOCK_LISTS_H
 #define _SHERLOCK_LISTS_H
 
+/*
+ * I admit the list structure is very tricky and also somewhat awkward,
+ * but it's both efficient and easy to manipulate once one understands the
+ * basic trick: The list head always contains two synthetic nodes which are
+ * always present in the list: the head and the tail. But as the `next'
+ * entry of the tail and the `prev' entry of the head are both NULL, the
+ * nodes can overlap each other:
+ *
+ *     head    head_node.next
+ *     null    head_node.prev  tail_node.next
+ *     tail                    tail_node.prev
+ */
+      
 typedef struct node {
   struct node *next, *prev;
 } node;