1 files changed, 60 insertions, 0 deletions
diff --git a/src/shared/ring.c b/src/shared/ring.c
new file mode 100644
index 0000000..44c73f6
--- /dev/null
+++ b/src/shared/ring.c
@@ -0,0 +1,60 @@
+#include <shared/ring.h>
+#include <shared/mem.h>
+#include <stdbool.h>
+
+static bool at_end(ring_t *r) {
+	return  r->_head + 1 == r->_tail
+		|| (r->_head + 1 == r->capacity && r->_tail == 0);
+}
+
+size_t ring_used(ring_t *r) {
+	if (r->_head >= r->_tail)
+		return r->_head - r->_tail;
+	else
+		return r->_head + r->capacity - r->_tail;
+}
+
+size_t ring_avail(ring_t *r) {
+	return r->capacity - ring_used(r);
+}
+
+void ring_put(ring_t *r, const void *buf, size_t len) {
+	// TODO do something similar to ring_get
+	for (size_t i = 0; i < len; i++)
+		ring_put1b(r, ((uint8_t*)buf)[i]);
+}
+
+void ring_put1b(ring_t *r, uint8_t byte) {
+	if (at_end(r)) return;
+	r->buf[r->_head++] = byte;
+	if (r->_head >= r->capacity) r->_head = 0;
+}
+
+size_t ring_get(ring_t *r, void *buf, size_t len) {
+	size_t read = 0;
+	size_t plen;
+	void *pbuf;
+	for (size_t i = 0; i < 2; i++) {
+		plen = len - read;
+		pbuf = ring_contig(r, &plen);
+		if (buf) memcpy(buf + read, pbuf, plen);
+		read += plen;
+	}
+	return read;
+}
+
+void *ring_contig(ring_t *r, size_t *len) {
+	void *ret = &r->buf[r->_tail];
+	size_t avail;
+	if (r->_head >= r->_tail)
+		avail = r->_head - r->_tail;
+	else
+		avail = r->capacity - r->_tail;
+
+	if (*len > avail)
+		*len = avail;
+
+	r->_tail += *len;
+	if (r->_tail >= r->capacity) r->_tail = 0;
+	return ret;
+}