[COMMIT seastar master] websocket: rewrite send_data without sstring

[Commit Bot]

From: Piotr Sarna <sa...@scylladb.com>
Committer: Piotr Sarna <sa...@scylladb.com>
Branch: master

websocket: rewrite send_data without sstring

In order to get rid of unnecessary operations on sstring,
the header is now built on top of a char array.
It's up to 10 bytes total, so it doesn't really need to be built
on the heap.

---
diff --git a/src/websocket/server.cc b/src/websocket/server.cc
--- a/src/websocket/server.cc
+++ b/src/websocket/server.cc
@@ -25,6 +25,7 @@
#include <cryptopp/filters.h>
#include <cryptopp/base64.h>
#include <seastar/core/scattered_message.hh>
+#include <seastar/core/byteorder.hh>

#ifndef CRYPTOPP_NO_GLOBAL_BYTE
namespace CryptoPP {
@@ -340,30 +341,25 @@ future<> connection::close(bool send_close) {
}

future<> connection::send_data(opcodes opcode, temporary_buffer<char>&& buff) {
- sstring data;
- {
- char first_byte[] = "\x80";
- first_byte[0] += opcode;
- data.append(first_byte, 1);
- }
+ char header[10] = {'\x80', 0};
+ size_t header_size = 2;
+
+ header[0] += opcode;

if ((126 <= buff.size()) && (buff.size() <= std::numeric_limits<uint16_t>::max())) {
- uint16_t length = buff.size();
- length = htobe16(length);
- data.append("\x7e", 1);
- data.append(reinterpret_cast<char*>(&length), sizeof(uint16_t));
+ header[1] = '\x7e';
+ write_be<uint16_t>(header + 2, buff.size());
+ header_size = 3;
} else if (std::numeric_limits<uint16_t>::max() < buff.size()) {
- uint64_t length = buff.size();
- length = htobe64(length);
- data.append("\x7f", 1);
- data.append(reinterpret_cast<char*>(&length), sizeof(uint64_t));
+ header[1] = '\x7e';
+ write_be<uint64_t>(header + 2, buff.size());
+ header_size = 10;
} else {
- uint8_t length = buff.size() & 0x7F;
- data.append(reinterpret_cast<char*>(&length), sizeof(uint8_t));
+ header[1] = uint8_t(buff.size());
}

scattered_message<char> msg;
- msg.append(std::move(data));
+ msg.append(sstring(header, header_size));
msg.append(std::move(buff));
return _write_buf.write(std::move(msg)).then([this] {
return _write_buf.flush();