stream: Add a cork to pause sending

include/stream.h

@@ -21,6 +21,7 @@
 #include "rcbuf.h"
 
 #include <stdint.h>
+#include <stdbool.h>
 
 #ifdef ENABLE_TLS
 #include <gnutls/gnutls.h>
@@ -65,6 +66,7 @@ struct stream_impl {
 	ssize_t (*read)(struct stream*, void* dst, size_t size);
 	int (*send)(struct stream*, struct rcbuf* payload,
 			stream_req_fn on_done, void* userdata);
+	int (*send_first)(struct stream*, struct rcbuf* payload);
 };
 
 struct stream {
@@ -85,6 +87,8 @@ struct stream {
 
 	uint32_t bytes_sent;
 	uint32_t bytes_received;
+
+	bool cork;
 };
 
 struct stream* stream_new(int fd, stream_event_fn on_event, void* userdata);
@@ -95,6 +99,7 @@ int stream_write(struct stream* self, const void* payload, size_t len,
                  stream_req_fn on_done, void* userdata);
 int stream_send(struct stream* self, struct rcbuf* payload,
                 stream_req_fn on_done, void* userdata);
+int stream_send_first(struct stream* self, struct rcbuf* payload);
 
 #ifdef ENABLE_TLS
 int stream_upgrade_to_tls(struct stream* self, void* context);

src/stream-tcp.c

@@ -60,6 +60,9 @@ static void stream_tcp_destroy(struct stream* self)
 
 static int stream_tcp__flush(struct stream* self)
 {
+	if (self->cork)
+		return 0;
+
 	static struct iovec iov[IOV_MAX];
 	size_t n_msgs = 0;
 	ssize_t bytes_sent;
@@ -195,11 +198,27 @@ static int stream_tcp_send(struct stream* self, struct rcbuf* payload,
 	return stream_tcp__flush(self);
 }
 
+static int stream_tcp_send_first(struct stream* self, struct rcbuf* payload)
+{
+	if (self->state == STREAM_STATE_CLOSED)
+		return -1;
+
+	struct stream_req* req = calloc(1, sizeof(*req));
+	if (!req)
+		return -1;
+
+	req->payload = payload;
+	TAILQ_INSERT_HEAD(&self->send_queue, req, link);
+
+	return stream_tcp__flush(self);
+}
+
 static struct stream_impl impl = {
 	.close = stream_tcp_close,
 	.destroy = stream_tcp_destroy,
 	.read = stream_tcp_read,
 	.send = stream_tcp_send,
+	.send_first = stream_tcp_send_first,
 };
 
 struct stream* stream_new(int fd, stream_event_fn on_event, void* userdata)

src/stream.c

@@ -37,6 +37,12 @@ int stream_send(struct stream* self, struct rcbuf* payload,
 	return self->impl->send(self, payload, on_done, userdata);
 }
 
+int stream_send_first(struct stream* self, struct rcbuf* payload)
+{
+	assert(self->impl && self->impl->send);
+	return self->impl->send_first(self, payload);
+}
+
 int stream_write(struct stream* self, const void* payload, size_t len,
                  stream_req_fn on_done, void* userdata)
 {