# HG changeset patch
# User Kim Alvefur <zash@zash.se>
# Date 1625761319 -7200
# Node ID 735b8f4a6d7e127e950212a63cf91efbffd97993
# Parent  68f0196ece2aac3add7642040aba5799a4612f2e
net.http: Send entire HTTP request header as one write

When opportunistic writes are enabled this reduces the number of
syscalls and TCP packets sent on the wire.

Experiments with TCP Fast Open made this even more obvious.

That table trick probably wasn't as efficient. Lua generates bytecode
for a table with zero array slots and space for two entries in the hash
part, plus code to set [2] and [4]. I didn't verify but I suspect it
would have had to resize the table when setting [1] and [3], although
probably only once. Concatenating the strings directly in Lua is easier
to read and involves no extra table or function call.

diff -r 68f0196ece2a -r 735b8f4a6d7e net/http.lua
--- a/net/http.lua	Thu Jul 08 17:57:44 2021 +0200
+++ b/net/http.lua	Thu Jul 08 18:21:59 2021 +0200
@@ -164,13 +164,11 @@
 		t_insert(request_line, 4, "?"..req.query);
 	end
 
+	for k, v in pairs(req.headers) do
+		t_insert(request_line, k .. ": " .. v .. "\r\n");
+	end
+	t_insert(request_line, "\r\n")
 	conn:write(t_concat(request_line));
-	local t = { [2] = ": ", [4] = "\r\n" };
-	for k, v in pairs(req.headers) do
-		t[1], t[3] = k, v;
-		conn:write(t_concat(t));
-	end
-	conn:write("\r\n");
 
 	if req.body then
 		conn:write(req.body);