unix: Implement SO_RCVBUF

Implemented `UnixBufferQueue::SetCapacity` so that `setsockopt`
with `SO_RCVBUF` will not always return an error.

Change-Id: I2d9be84633f84474fac64b379e9f89ef2751a094
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6816
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/kernel/util/ring_buffer.h

@@ -44,6 +44,7 @@ ssize_t ring_buffer_user_write(struct ring_buffer *buffer, const uint8 *data, ss
 size_t ring_buffer_peek(struct ring_buffer *buffer, size_t offset, void *data,
 			size_t length);
 int32 ring_buffer_get_vecs(struct ring_buffer *buffer, struct iovec *vecs);
+size_t ring_buffer_move(struct ring_buffer *to, ssize_t length, struct ring_buffer *from);
 
 #ifdef __cplusplus
 }

src/add-ons/kernel/network/protocols/unix/UnixFifo.cpp

@@ -316,8 +316,20 @@ UnixBufferQueue::Write(UnixRequest& request)
 status_t
 UnixBufferQueue::SetCapacity(size_t capacity)
 {
-// TODO:...
-return B_ERROR;
+	if (capacity <= fCapacity)
+		return B_OK;
+
+	ring_buffer* newBuffer = create_ring_buffer(capacity);
+	if (newBuffer == NULL)
+		return B_NO_MEMORY;
+
+	ring_buffer_move(newBuffer, ring_buffer_readable(fBuffer), fBuffer);
+	delete_ring_buffer(fBuffer);
+
+	fBuffer = newBuffer;
+	fCapacity = capacity;
+
+	return B_OK;
 }
 
 

src/system/kernel/util/ring_buffer.cpp

@@ -302,6 +302,47 @@ ring_buffer_get_vecs(struct ring_buffer* buffer, struct iovec* vecs)
 }
 
 
+/*! Moves data from one ring buffer to another.
+
+	\param to The destination ring buffer.
+	\param length The maximum number of bytes to move.
+	\param from The source ring buffer.
+	\return The number of bytes actually moved.
+*/
+size_t
+ring_buffer_move(struct ring_buffer *to, ssize_t length,
+	struct ring_buffer *from)
+{
+	if (length > from->in)
+		length = from->in;
+
+	if (length > (to->size - to->in))
+		length = to->size - to->in;
+
+	size_t bytesMoved = 0;
+
+	if ((from->first + length) <= from->size) {
+		// simple move
+		bytesMoved = ring_buffer_write(to, from->buffer + from->first, length);
+	} else {
+		// need to move both ends
+		size_t upper = from->size - from->first;
+		size_t lower = length - upper;
+
+		bytesMoved = ring_buffer_write(to, from->buffer + from->first, upper);
+		if (bytesMoved == upper) {
+			// only continue writing if the first part was completely written
+			bytesMoved += ring_buffer_write(to, from->buffer, lower);
+		}
+	}
+
+	from->first = (from->first + bytesMoved) % from->size;
+	from->in -= bytesMoved;
+
+	return bytesMoved;
+}
+
+
 #if 0
 /**	Sends the contents of the ring buffer to a port.
  *	The buffer will be empty afterwards only if sending the data actually works.