lib: add ring buffer

Simple ring buffer implementation useful for fixed size FIFO queues.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/lib/ringbuf.c b/lib/ringbuf.c
new file mode 100644
index 0000000000..fee5b5d691
--- /dev/null
+++ b/lib/ringbuf.c
@@ -0,0 +1,104 @@
+/*
+ * Circular buffer implementation.
+ * Copyright (C) 2017 Cumulus Networks
+ * Quentin Young
+ *
+ * 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 2 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; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <zebra.h>
+
+#include "ringbuf.h"
+#include "memory.h"
+
+DEFINE_MTYPE_STATIC(LIB, RINGBUFFER, "Ring buffer")
+
+struct ringbuf *ringbuf_new(size_t size)
+{
+	struct ringbuf *buf = XCALLOC(MTYPE_RINGBUFFER, sizeof(struct ringbuf));
+	buf->data = XCALLOC(MTYPE_RINGBUFFER, size);
+	buf->size = size;
+	buf->empty = true;
+	return buf;
+}
+
+void ringbuf_del(struct ringbuf *buf)
+{
+	XFREE(MTYPE_RINGBUFFER, buf->data);
+	XFREE(MTYPE_RINGBUFFER, buf);
+}
+
+size_t ringbuf_remain(struct ringbuf *buf)
+{
+	ssize_t diff = buf->end - buf->start;
+	diff += ((diff == 0) && !buf->empty) ? buf->size : 0;
+	diff += (diff < 0) ? buf->size : 0;
+	return (size_t)diff;
+}
+
+size_t ringbuf_space(struct ringbuf *buf)
+{
+	return buf->size - ringbuf_remain(buf);
+}
+
+size_t ringbuf_put(struct ringbuf *buf, const void *data, size_t size)
+{
+	const uint8_t *dp = data;
+	size_t space = ringbuf_space(buf);
+	size_t copysize = MIN(size, space);
+	size_t tocopy = copysize;
+	if (tocopy > buf->size - buf->end) {
+		size_t ts = buf->size - buf->end;
+		memcpy(buf->data + buf->end, dp, ts);
+		buf->end = 0;
+		tocopy -= ts;
+		dp += ts;
+	}
+	memcpy(buf->data + buf->end, dp, tocopy);
+	buf->end += tocopy;
+	buf->empty = (buf->start == buf->end) && (buf->empty && !copysize);
+	return copysize;
+}
+
+size_t ringbuf_get(struct ringbuf *buf, void *data, size_t size)
+{
+	uint8_t *dp = data;
+	size_t remain = ringbuf_remain(buf);
+	size_t copysize = MIN(remain, size);
+	size_t tocopy = copysize;
+	if (tocopy > buf->size - buf->start) {
+		size_t ts = buf->size - buf->start;
+		memcpy(dp, buf->data + buf->start, ts);
+		buf->start = 0;
+		tocopy -= ts;
+		dp += ts;
+	}
+	memcpy(dp, buf->data + buf->start, tocopy);
+	buf->start = buf->start + tocopy;
+	buf->empty = (buf->start == buf->end) && (buf->empty || copysize);
+	return copysize;
+}
+
+void ringbuf_reset(struct ringbuf *buf)
+{
+	buf->start = buf->end = 0;
+	buf->empty = true;
+}
+
+void ringbuf_wipe(struct ringbuf *buf)
+{
+	memset(buf->data, 0x00, buf->size);
+	ringbuf_reset(buf);
+	buf->empty = true;
+}