From ab4afe15873e064272524ea8cc91010edb22f9aa Mon Sep 17 00:00:00 2001
From: Jordan Bancino <jordan@bancino.net>
Date: Wed, 24 Aug 2022 09:06:27 -0400
Subject: [PATCH] Add basic Queue implementation.

---
 src/Queue.c         | 164 ++++++++++++++++++++++++++++++++++++++++++++
 src/include/Queue.h |  50 ++++++++++++++
 2 files changed, 214 insertions(+)
 create mode 100644 src/Queue.c
 create mode 100644 src/include/Queue.h

diff --git a/src/Queue.c b/src/Queue.c
new file mode 100644
index 0000000..db40faa
--- /dev/null
+++ b/src/Queue.c
@@ -0,0 +1,164 @@
+/*
+ * Copyright (C) 2022 Jordan Bancino <@jordan:bancino.net>
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include <Queue.h>
+
+struct Queue
+{
+    void **items;
+    size_t size;
+    int front;
+    int rear;
+};
+
+Queue *
+QueueCreate(size_t size)
+{
+    Queue *q;
+
+    if (!size)
+    {
+        /* Can't have a queue of length zero */
+        return NULL;
+    }
+
+    q = malloc(sizeof(Queue));
+    if (!q)
+    {
+        return NULL;
+    }
+
+    q->items = malloc(size * sizeof(void *));
+    if (!q->items)
+    {
+        free(q);
+        return NULL;
+    }
+
+    q->size = size;
+    q->front = -1;
+    q->rear = -1;
+}
+
+void
+QueueFree(Queue * q)
+{
+    if (q)
+    {
+        free(q->items);
+    }
+
+    free(q);
+}
+
+int
+QueueFull(Queue *)
+{
+    if (!q)
+    {
+        return 0;
+    }
+
+    return ((q->front == q->rear + 1) || (q->front == 0 && q->rear == q->size - 1));
+}
+
+int
+QueueEmpty(Queue *)
+{
+    if (!q)
+    {
+        return 0;
+    }
+
+    return q->front == -1;
+}
+
+int
+QueuePush(Queue * q, void *element)
+{
+    if (!q || !element)
+    {
+        return 0;
+    }
+
+    if (QueueFull(q))
+    {
+        return 0;
+    }
+
+    if (q->front == -1)
+    {
+        q->front = 0;
+    }
+
+    q->rear = (q->rear + 1) % q->size;
+    q->items[q->rear] = element;
+
+    return 1;
+}
+
+void *
+QueuePop(Queue * q)
+{
+    void *element;
+
+    if (!q)
+    {
+        return NULL;
+    }
+
+    if (QueueEmpty(q))
+    {
+        return NULL;
+    }
+
+    element = q->items[q->front];
+
+    if (q->front == q->rear)
+    {
+        q->front = -1;
+        q->rear = -1;
+    }
+    else
+    {
+        q->front = (q->front + 1) % q->size;
+    }
+
+    return element;
+}
+
+void *
+QueuePeek(Queue * q)
+{
+    if (!q)
+    {
+        return NULL;
+    }
+
+    if (QueueEmpty(q))
+    {
+        return NULL;
+    }
+
+    return q->items[q->front];
+}
diff --git a/src/include/Queue.h b/src/include/Queue.h
new file mode 100644
index 0000000..a67b437
--- /dev/null
+++ b/src/include/Queue.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2022 Jordan Bancino <@jordan:bancino.net>
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef TELODENDRIA_QUEUE_H
+#define TELODENDRIA_QUEUE_H
+
+typedef struct Queue Queue;
+
+extern Queue *
+ QueueCreate(size_t);
+
+extern void
+ QueueFree(Queue *);
+
+extern int
+ QueuePush(Queue *, void *);
+
+extern void *
+ QueuePop(Queue *);
+
+extern void *
+ QueuePeek(Queue *);
+
+extern int
+ QueueFull(Queue *);
+
+extern int
+ QueueEmpty(Queue *);
+
+#endif