pkg: add generic linked list iterator code

iter.h

@@ -0,0 +1,66 @@
+/*
+ * iter.h
+ * Linked lists and iterators.
+ *
+ * Copyright (c) 2013 pkgconf authors (see AUTHORS).
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#ifndef PKGCONF__ITER_H
+#define PKGCONF__ITER_H
+
+typedef struct pkg_node_ pkg_node_t;
+
+struct pkg_node_ {
+	pkg_node_t *prev, *next;
+	void *data;
+};
+
+typedef struct {
+	pkg_node_t *head, *tail;
+} pkg_list_t;
+
+static inline void
+pkg_node_insert(pkg_node_t *node, void *data, pkg_list_t *list)
+{
+	pkg_node_t *tnode;
+
+	node->data = data;
+
+	if (list->head == NULL)
+	{
+		list->head = node;
+		list->tail = node;
+		return;
+	}
+
+	tnode = list->head;
+
+	node->next = tnode;
+	tnode->prev = node;
+
+	list->head = node;
+}
+
+static inline void
+pkg_node_delete(pkg_node_t *node, pkg_list_t *list)
+{
+	if (node->prev == NULL)
+		list->head = node->next;
+	else
+		node->prev->next = node->next;
+
+	if (node->next == NULL)
+		list->tail = node->prev;
+	else
+		node->next->prev = node->prev;
+}
+
+#endif

pkg.h

@@ -18,6 +18,7 @@
 
 #include "config.h"
 #include "stdinc.h"
+#include "iter.h"
 
 #define PKG_BUFSIZE	(65535)