7 files changed, 22 insertions, 13 deletions
diff --git a/src/kernel/arch/amd64/driver/ps2.c b/src/kernel/arch/amd64/driver/ps2.c
index 35165d9..9148c98 100644
--- a/src/kernel/arch/amd64/driver/ps2.c
+++ b/src/kernel/arch/amd64/driver/ps2.c
@@ -91,7 +91,7 @@ enum {
 };
 
 static void read_backlog(struct vfs_request *req, ring_t *r, struct vfs_request **queue) {
-	if (ring_size(r) == 0) {
+	if (ring_used(r) == 0) {
 		/* nothing to read, join queue */
 		assert(!req->postqueue_next);
 		while (*queue) queue = &(*queue)->postqueue_next;
diff --git a/src/kernel/arch/amd64/driver/serial.c b/src/kernel/arch/amd64/driver/serial.c
index b3bfe29..cf21b61 100644
--- a/src/kernel/arch/amd64/driver/serial.c
+++ b/src/kernel/arch/amd64/driver/serial.c
@@ -72,7 +72,7 @@ static void accept(struct vfs_request *req) {
 			vfsreq_finish_short(req, valid ? 0 : -1);
 			break;
 		case VFSOP_READ:
-			if (ring_size((void*)&backlog) == 0) {
+			if (ring_used((void*)&backlog) == 0) {
 				/* nothing to read, join queue */
 				assert(!req->postqueue_next);
 				struct vfs_request **slot = &blocked_on;
diff --git a/src/shared/container/ring.c b/src/shared/container/ring.c
index 67944b0..21c63a1 100644
--- a/src/shared/container/ring.c
+++ b/src/shared/container/ring.c
@@ -7,13 +7,17 @@ static bool at_end(ring_t *r) {
 		|| (r->_head + 1 == r->capacity && r->_tail == 0);
 }
 
-size_t ring_size(ring_t *r) {
+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, void *buf, size_t len) {
 	// TODO do something similar to ring_get
 	for (size_t i = 0; i < len; i++)
diff --git a/src/shared/container/ring.h b/src/shared/container/ring.h
index bc978ce..4f0d310 100644
--- a/src/shared/container/ring.h
+++ b/src/shared/container/ring.h
@@ -8,7 +8,10 @@ typedef struct {
 	size_t _head, _tail;
 } ring_t;
 
-size_t	ring_size(ring_t*);
+/** Returns amount of bytes stored in the buffer. */
+size_t	ring_used(ring_t*);
+/** Returns amount of space left in the buffer. */
+size_t	ring_avail(ring_t*);
 
 void	ring_put(ring_t*, void*, size_t);
 void	ring_put1b(ring_t*, uint8_t);
diff --git a/src/user/app/drawmouse/drawmouse.c b/src/user/app/drawmouse/drawmouse.c
index 7e7c55b..47e8e8a 100644
--- a/src/user/app/drawmouse/drawmouse.c
+++ b/src/user/app/drawmouse/drawmouse.c
@@ -66,7 +66,7 @@ int main(void) {
 		int len = _syscall_read(fd, buf, sizeof buf, 0);
 		if (len == 0) break;
 		ring_put(&r, buf, len);
-		while (ring_size(&r) >= 3) {
+		while (ring_used(&r) >= 3) {
 			struct packet p;
 			ring_get(&r, &p, sizeof p);
 			p.dy *= -1;
diff --git a/src/user/app/init/driver/ps2.c b/src/user/app/init/driver/ps2.c
index 961ea53..85b83b7 100644
--- a/src/user/app/init/driver/ps2.c
+++ b/src/user/app/init/driver/ps2.c
@@ -61,7 +61,7 @@ static void main_loop(void) {
 				break;
 
 			case VFSOP_READ:
-				while (ring_size((void*)&backlog) == 0) {
+				while (ring_used((void*)&backlog) == 0) {
 					/* read raw input until we have something to output */
 					int len = _syscall_read(fd, buf, sizeof buf, 0);
 					if (len == 0) break;
diff --git a/src/user/app/tests/shared/ringbuf.c b/src/user/app/tests/shared/ringbuf.c
index 7330bbe..d4e8dc9 100644
--- a/src/user/app/tests/shared/ringbuf.c
+++ b/src/user/app/tests/shared/ringbuf.c
@@ -11,34 +11,36 @@ static void test_ringbuf(void) {
 
 	/* aliasing */
 	for (size_t i = 0; i < 16; i++) {
-		test(ring_size(&r) == 0);
+		test(ring_used(&r) == 0);
+		test(ring_avail(&r) == 16);
 		ring_put(&r, "11 bytes...", 11);
-		test(ring_size(&r) == 11);
+		test(ring_used(&r) == 11);
+		test(ring_avail(&r) == 5);
 
 		memset(cmpbuf, 0, sizeof cmpbuf);
 		test(ring_get(&r, cmpbuf, 16) == 11);
 		test(memcmp(cmpbuf, "11 bytes...", 11) == 0);
 	}
 
-	test(ring_size(&r) == 0);
+	test(ring_used(&r) == 0);
 	for (size_t i = 0; i < 7; i++)
 		ring_put1b(&r, num_written++);
-	test(ring_size(&r) == 7);
+	test(ring_used(&r) == 7);
 	for (size_t i = 0; i < 3; i++) {
 		ring_get(&r, &c, 1);
 		test(num_read++ == c);
 	}
-	test(ring_size(&r) == 4);
+	test(ring_used(&r) == 4);
 
 	for (size_t j = 0; j < 40; j++) {
 		for (size_t i = 0; i < 7; i++)
 			ring_put1b(&r, num_written++ & 0xff);
-		test(ring_size(&r) == 11);
+		test(ring_used(&r) == 11);
 		for (size_t i = 0; i < 7; i++) {
 			ring_get(&r, &c, 1);
 			test((num_read++ & 0xff) == c);
 		}
-		test(ring_size(&r) == 4);
+		test(ring_used(&r) == 4);
 	}
 }