1 files changed, 94 insertions, 0 deletions
diff --git a/src/list.h b/src/list.h
new file mode 100644
index 0000000..7249f9f
--- /dev/null
+++ b/src/list.h
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2012-2021 Robin Haberkorn
+ *
+ * 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/>.
+ */
+#pragma once
+
+typedef struct teco_stailq_entry_t {
+	struct teco_stailq_entry_t *next;
+} teco_stailq_entry_t;
+
+typedef struct {
+	/** Pointer to the first element or NULL */
+	teco_stailq_entry_t *first;
+	/** Pointer to the last element's `next` field or the head's `first` field */
+	teco_stailq_entry_t **last;
+} teco_stailq_head_t;
+
+#define TECO_STAILQ_HEAD_INITIALIZER(HEAD) ((teco_stailq_head_t){NULL, &(HEAD)->first})
+
+static inline void
+teco_stailq_insert_tail(teco_stailq_head_t *head, teco_stailq_entry_t *entry)
+{
+	entry->next = NULL;
+	*head->last = entry;
+	head->last = &entry->next;
+}
+
+static inline teco_stailq_entry_t *
+teco_stailq_remove_head(teco_stailq_head_t *head)
+{
+	teco_stailq_entry_t *first = head->first;
+	if (first && !(head->first = first->next))
+		head->last = &head->first;
+	return first;
+}
+
+/** Can be both a tail queue head or an entry (tail queue element). */
+typedef union teco_tailq_entry_t {
+	struct {
+		/** Pointer to the next entry or NULL */
+		union teco_tailq_entry_t *next;
+		/** Pointer to the previous entry or to the queue head */
+		union teco_tailq_entry_t *prev;
+	};
+
+	struct {
+		/** Pointer to the first entry or NULL */
+		union teco_tailq_entry_t *first;
+		/** Pointer to the last entry or to the queue head */
+		union teco_tailq_entry_t *last;
+	};
+} teco_tailq_entry_t;
+
+#define TECO_TAILQ_HEAD_INITIALIZER(HEAD) ((teco_tailq_entry_t){.first = NULL, .last = (HEAD)})
+
+static inline void
+teco_tailq_insert_before(teco_tailq_entry_t *entry_a, teco_tailq_entry_t *entry_b)
+{
+	entry_b->prev = entry_a->prev;
+	entry_b->next = entry_a;
+	entry_a->prev->next = entry_b;
+	entry_a->prev = entry_b;
+}
+
+static inline void
+teco_tailq_insert_tail(teco_tailq_entry_t *head, teco_tailq_entry_t *entry)
+{
+	entry->next = NULL;
+	entry->prev = head->last;
+	head->last->next = entry;
+	head->last = entry;
+}
+
+static inline void
+teco_tailq_remove(teco_tailq_entry_t *head, teco_tailq_entry_t *entry)
+{
+	if (entry->next)
+		entry->next->prev = entry->prev;
+	else
+		head->last = entry->prev;
+	entry->prev->next = entry->next;
+}