From faf6a5df9597d59b1e9d9dd60a6c6b9cc9a3608a Mon Sep 17 00:00:00 2001
From: Povilas Kanapickas <povilas@radix.lt>
Date: Sat, 14 Dec 2024 20:34:34 +0200
Subject: [PATCH] websocket: Convert connection::read_http_upgrade_request() to
 use coros

Using coroutines improves readability of the code. The function is not
performance sensitive as well, as it's called only during connection
establishment.

Closes scylladb/seastar#2583
---
 src/websocket/server.cc | 87 +++++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 46 deletions(-)

diff --git a/src/websocket/server.cc b/src/websocket/server.cc
index f9c26bfe29..7dbaa6a696 100644
--- a/src/websocket/server.cc
+++ b/src/websocket/server.cc
@@ -147,55 +147,50 @@ static std::string sha1_base64(std::string_view source) {
 
 future<> connection::read_http_upgrade_request() {
     _http_parser.init();
-    return _read_buf.consume(_http_parser).then([this] () mutable {
-        if (_http_parser.eof()) {
-            _done = true;
-            return make_ready_future<>();
-        }
-        std::unique_ptr<http::request> req = _http_parser.get_parsed_request();
-        if (_http_parser.failed()) {
-            return make_exception_future<>(websocket::exception("Incorrect upgrade request"));
-        }
+    co_await _read_buf.consume(_http_parser);
 
-        sstring upgrade_header = req->get_header("Upgrade");
-        if (upgrade_header != "websocket") {
-            return make_exception_future<>(websocket::exception("Upgrade header missing"));
-        }
+    if (_http_parser.eof()) {
+        _done = true;
+        co_return;
+    }
+    std::unique_ptr<http::request> req = _http_parser.get_parsed_request();
+    if (_http_parser.failed()) {
+        throw websocket::exception("Incorrect upgrade request");
+    }
 
-        sstring subprotocol = req->get_header("Sec-WebSocket-Protocol");
-        if (subprotocol.empty()) {
-            return make_exception_future<>(websocket::exception("Subprotocol header missing."));
-        }
+    sstring upgrade_header = req->get_header("Upgrade");
+    if (upgrade_header != "websocket") {
+        throw websocket::exception("Upgrade header missing");
+    }
 
-        if (!_server.is_handler_registered(subprotocol)) {
-            return make_exception_future<>(websocket::exception("Subprotocol not supported."));
-        }
-        this->_handler = this->_server._handlers[subprotocol];
-        this->_subprotocol = subprotocol;
-        wlogger.debug("Sec-WebSocket-Protocol: {}", subprotocol);
-
-        sstring sec_key = req->get_header("Sec-Websocket-Key");
-        sstring sec_version = req->get_header("Sec-Websocket-Version");
-
-        sstring sha1_input = sec_key + magic_key_suffix;
-
-        wlogger.debug("Sec-Websocket-Key: {}, Sec-Websocket-Version: {}", sec_key, sec_version);
-
-        std::string sha1_output = sha1_base64(sha1_input);
-        wlogger.debug("SHA1 output: {} of size {}", sha1_output, sha1_output.size());
-
-        return _write_buf.write(http_upgrade_reply_template).then([this, sha1_output = std::move(sha1_output)] {
-            return _write_buf.write(sha1_output);
-        }).then([this] {
-            return _write_buf.write("\r\nSec-WebSocket-Protocol: ", 26);
-        }).then([this] {
-            return _write_buf.write(_subprotocol);
-        }).then([this] {
-            return _write_buf.write("\r\n\r\n", 4);
-        }).then([this] {
-            return _write_buf.flush();
-        });
-    });
+    sstring subprotocol = req->get_header("Sec-WebSocket-Protocol");
+    if (subprotocol.empty()) {
+        throw websocket::exception("Subprotocol header missing.");
+    }
+
+    if (!_server.is_handler_registered(subprotocol)) {
+        throw websocket::exception("Subprotocol not supported.");
+    }
+    this->_handler = this->_server._handlers[subprotocol];
+    this->_subprotocol = subprotocol;
+    wlogger.debug("Sec-WebSocket-Protocol: {}", subprotocol);
+
+    sstring sec_key = req->get_header("Sec-Websocket-Key");
+    sstring sec_version = req->get_header("Sec-Websocket-Version");
+
+    sstring sha1_input = sec_key + magic_key_suffix;
+
+    wlogger.debug("Sec-Websocket-Key: {}, Sec-Websocket-Version: {}", sec_key, sec_version);
+
+    std::string sha1_output = sha1_base64(sha1_input);
+    wlogger.debug("SHA1 output: {} of size {}", sha1_output, sha1_output.size());
+
+    co_await _write_buf.write(http_upgrade_reply_template);
+    co_await _write_buf.write(sha1_output);
+    co_await _write_buf.write("\r\nSec-WebSocket-Protocol: ", 26);
+    co_await _write_buf.write(_subprotocol);
+    co_await _write_buf.write("\r\n\r\n", 4);
+    co_await _write_buf.flush();
 }
 
 future<websocket_parser::consumption_result_t> websocket_parser::operator()(