From 69c9b2c9cab6c1ef6ae4ba7f26d53480ae919ffb Mon Sep 17 00:00:00 2001
From: Midgard <midgard@zeus.ugent.be>
Date: Wed, 29 Jan 2020 14:45:48 +0100
Subject: [PATCH] Add ringbuffer data structure

---
 kernel/util/ringbuffer.c | 85 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 kernel/util/ringbuffer.c

diff --git a/kernel/util/ringbuffer.c b/kernel/util/ringbuffer.c
new file mode 100644
index 0000000..27ff0f7
--- /dev/null
+++ b/kernel/util/ringbuffer.c
@@ -0,0 +1,85 @@
+#ifndef RINGBUFFER_C
+#define RINGBUFFER_C
+
+#include <stdbool.h>
+#include "../alloc.c"
+
+/*
+ * Data layout:       ↓head
+ * [ 4, undef, undef, 1, 2, 3 ]  (1 is first added etc.)
+ * So enqueue adds after 4 and dequeue removes 1.
+ */
+struct ringbuffer {
+	int head;
+	int size;
+	void** buffer;
+	int buffer_n;
+};
+
+void rbfr_clear(struct ringbuffer* this) {
+	this->size = 0;
+	this->head = 0;
+}
+
+struct ringbuffer* rbfr_create(const int capacity) {
+	struct ringbuffer* const this = alloc(sizeof (struct ringbuffer));
+
+	this->buffer = alloc(capacity * sizeof (void*));
+	this->buffer_n = capacity;
+	rbfr_clear(this);
+
+	return this;
+}
+
+void rbfr_destroy(struct ringbuffer* this) {
+	free(this->buffer);
+	free(this);
+}
+
+int rbfr_size(const struct ringbuffer* this) {
+	return this->size;
+}
+
+int rbfr_capacity(const struct ringbuffer* this) {
+	return this->buffer_n;
+}
+
+void rbfr_enqueue(struct ringbuffer* this, void* element) {
+	if (this->buffer_n == 0) {
+		return;
+	}
+
+	int index = this->head + this->size;
+	if (index >= this->buffer_n) {
+		index -= this->buffer_n;
+	}
+	this->buffer[index] = element;
+	if (this->size < this->buffer_n) {
+		this->size++;
+	} else {
+		this->head++;
+	}
+	return;
+}
+
+bool rbfr_peek(const struct ringbuffer* this, void** element) {
+	if (this->size == 0) {
+		return false;
+	}
+	*element = this->buffer[this->head];
+	return true;
+}
+
+bool rbfr_dequeue(struct ringbuffer* this, void** element) {
+	if (!rbfr_peek(this, element)) {
+		return false;
+	}
+	this->size--;
+	this->head++;
+	if (this->head >= this->buffer_n) {
+		this->head = 0;
+	}
+	return true;
+}
+
+#endif // RINGBUFFER_C