kern/plist: new module

This module implements priority lists, useful to store entries sorted
by their priority.

1 files changed, 65 insertions, 0 deletions

diff --git a/kern/plist.c b/kern/plist.c
new file mode 100644
index 0000000..851de62
--- /dev/null
+++ b/kern/plist.c
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <kern/list.h>
+#include <kern/plist.h>
+
+void
+plist_add(struct plist *plist, struct plist_node *pnode)
+{
+    struct plist_node *next;
+
+    if (plist_empty(plist)) {
+        list_insert_head(&plist->list, &pnode->node);
+        list_insert_head(&plist->prio_list, &pnode->prio_node);
+        return;
+    }
+
+    list_for_each_entry(&plist->prio_list, next, prio_node) {
+        if (pnode->priority < next->priority) {
+            break;
+        }
+    }
+
+    if (list_end(&plist->prio_list, &next->prio_node)
+        || (pnode->priority != next->priority)) {
+        list_insert_before(&next->prio_node, &pnode->prio_node);
+    } else {
+        list_init(&pnode->prio_node);
+    }
+
+    list_insert_before(&next->node, &pnode->node);
+}
+
+void
+plist_remove(struct plist *plist, struct plist_node *pnode)
+{
+    struct plist_node *next;
+
+    if (!list_node_unlinked(&pnode->prio_node)) {
+        next = list_next_entry(pnode, node);
+
+        if (!list_end(&plist->list, &next->node)
+            && list_node_unlinked(&next->prio_node)) {
+            list_insert_after(&pnode->prio_node, &next->prio_node);
+        }
+
+        list_remove(&pnode->prio_node);
+    }
+
+    list_remove(&pnode->node);
+}