From 1b8ad3e1604d1b31f690668a4ed352d58b2621ef Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 20 Mar 2023 14:42:20 -0700
Subject: [PATCH] ircd::resource: Optimize response w/ iov for fused head and
 content.

---
 include/ircd/resource/response.h |  2 +-
 ircd/resource.cc                 | 36 +++++++++++++++++---------------
 2 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/include/ircd/resource/response.h b/include/ircd/resource/response.h
index ead3810e6..5de5be08e 100644
--- a/include/ircd/resource/response.h
+++ b/include/ircd/resource/response.h
@@ -39,7 +39,7 @@ struct ircd::resource::response
 	static const size_t HEAD_BUF_SZ;
 	static conf::item<std::string> access_control_allow_origin;
 
-	response(client &, const http::code &, const string_view &content_type, const size_t &content_length, const string_view &headers = {});
+	response(client &, const http::code &, const string_view &content_type, const size_t &content_length, const string_view &headers = {}, const string_view &content = {});
 	response(client &, const string_view &str, const string_view &content_type, const http::code &, const vector_view<const http::header> &);
 	response(client &, const string_view &str, const string_view &content_type, const http::code & = http::OK, const string_view &headers = {});
 	response(client &, const json::object &str, const http::code & = http::OK);
diff --git a/ircd/resource.cc b/ircd/resource.cc
index c105f0cc6..7b573fd26 100644
--- a/ircd/resource.cc
+++ b/ircd/resource.cc
@@ -1367,17 +1367,8 @@ ircd::resource::response::response(client &client,
 		content_type,
 		size(content),
 		headers,
+		content,
 	};
-
-	// All content gets sent
-	const size_t written
-	{
-		size(content)?
-			client.write_all(content):
-			0
-	};
-
-	assert(written == size(content));
 }
 
 decltype(ircd::resource::response::access_control_allow_origin)
@@ -1392,8 +1383,12 @@ ircd::resource::response::response(client &client,
                                    const http::code &code,
                                    const string_view &content_type,
                                    const size_t &content_length,
-                                   const string_view &headers)
+                                   const string_view &headers,
+                                   const string_view &content)
 {
+	// content may be empty if the caller wants to send it themselves, but
+	// either way the type and length must still be passed by caller.
+	assert(!content || content_length);
 	assert(!content_length || !empty(content_type));
 
 	const auto request_time
@@ -1430,13 +1425,20 @@ ircd::resource::response::response(client &client,
 	if(unlikely(!head.remaining()))
 		throw panic
 		{
-			"HTTP headers too large for buffer of %zu", sizeof(head_buf)
+			"HTTP headers too large for buffer of %zu",
+			sizeof(head_buf),
 		};
 
-	size_t wrote_head {0};
+	const const_buffer iov[]
+	{
+		head.completed(),
+		content,
+	};
+
+	size_t wrote {0};
 	std::exception_ptr eptr; try
 	{
-		wrote_head += client.write_all(head.completed());
+		wrote += client.write_all(iov);
 	}
 	catch(...)
 	{
@@ -1453,17 +1455,17 @@ ircd::resource::response::response(client &client,
 		log::logf
 		{
 			log, level,
-			"%s HTTP %u `%s' %s in %s; %s content-length:%s head-length:%zu %s%s",
+			"%s HTTP %u `%s' %s in %s; %s head:%zu content:%s %s%s",
 			loghead(client),
 			uint(code),
 			client.request.head.path,
 			http::status(code),
 			rtime,
 			content_type,
+			size(iov[0]),
 			ssize_t(content_length) >= 0?
 				lex_cast(content_length):
 				"chunked"_sv,
-			wrote_head,
 			eptr?
 				"error:"_sv:
 				string_view{},
@@ -1474,7 +1476,7 @@ ircd::resource::response::response(client &client,
 	if(unlikely(eptr))
 		std::rethrow_exception(eptr);
 
-	assert(wrote_head == size(head.completed()));
+	assert(wrote == buffers::size(vector_view(iov)));
 }
 
 ///////////////////////////////////////////////////////////////////////////////