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[wpinet] WebSocket: Reduce server send frame overhead

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Avoid allocating 4K buffer to send a 10-byte header per frame.
This commit is contained in:
Peter Johnson
2023-02-11 23:46:41 -08:00
parent b30664d630
commit 226ef35212
1 changed files with 37 additions and 21 deletions
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58
wpinet/src/main/native/cpp/WebSocket.cpp
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@@ -37,6 +37,9 @@ class WebSocketWriteReq : public uv::WriteReq {
std::function<void(std::span<uv::Buffer>, uv::Error)> m_callback;
SmallVector<uv::Buffer, 4> m_internalBufs;
SmallVector<uv::Buffer, 4> m_userBufs;
// for server
size_t m_internalBufPos = 0;
};
} // namespace
@@ -597,9 +600,6 @@ void WebSocket::HandleIncoming(uv::Buffer& buf, size_t size) {
static void WriteFrame(WebSocketWriteReq& req,
SmallVectorImpl<uv::Buffer>& bufs, bool server,
uint8_t opcode, std::span<const uv::Buffer> data) {
SmallVector<uv::Buffer, 4> internalBufs;
raw_uv_ostream os{internalBufs, 4096};
#ifdef WPINET_WEBSOCKET_VERBOSE_DEBUG
if ((opcode & 0x7f) == 0x01) {
SmallString<128> str;
@@ -619,8 +619,11 @@ static void WriteFrame(WebSocketWriteReq& req,
}
#endif
uint8_t header[10];
uint8_t* pHeader = header;
// opcode (includes FIN bit)
os << static_cast<unsigned char>(opcode);
*pHeader++ = opcode;
// payload length
uint64_t size = 0;
@@ -628,27 +631,30 @@ static void WriteFrame(WebSocketWriteReq& req,
size += buf.len;
}
if (size < 126) {
os << static_cast<unsigned char>((server ? 0x00 : kFlagMasking) | size);
*pHeader++ = (server ? 0x00 : kFlagMasking) | size;
} else if (size <= 0xffff) {
os << static_cast<unsigned char>((server ? 0x00 : kFlagMasking) | 126);
const uint8_t sizeMsb[] = {static_cast<uint8_t>((size >> 8) & 0xff),
static_cast<uint8_t>(size & 0xff)};
os << std::span{sizeMsb};
*pHeader++ = (server ? 0x00 : kFlagMasking) | 126;
*pHeader++ = (size >> 8) & 0xff;
*pHeader++ = size & 0xff;
} else {
os << static_cast<unsigned char>((server ? 0x00 : kFlagMasking) | 127);
const uint8_t sizeMsb[] = {static_cast<uint8_t>((size >> 56) & 0xff),
static_cast<uint8_t>((size >> 48) & 0xff),
static_cast<uint8_t>((size >> 40) & 0xff),
static_cast<uint8_t>((size >> 32) & 0xff),
static_cast<uint8_t>((size >> 24) & 0xff),
static_cast<uint8_t>((size >> 16) & 0xff),
static_cast<uint8_t>((size >> 8) & 0xff),
static_cast<uint8_t>(size & 0xff)};
os << std::span{sizeMsb};
*pHeader++ = (server ? 0x00 : kFlagMasking) | 127;
*pHeader++ = (size >> 56) & 0xff;
*pHeader++ = (size >> 48) & 0xff;
*pHeader++ = (size >> 40) & 0xff;
*pHeader++ = (size >> 32) & 0xff;
*pHeader++ = (size >> 24) & 0xff;
*pHeader++ = (size >> 16) & 0xff;
*pHeader++ = (size >> 8) & 0xff;
*pHeader++ = size & 0xff;
}
size_t headerSize = pHeader - header;
// clients need to mask the input data
if (!server) {
SmallVector<uv::Buffer, 4> internalBufs;
raw_uv_ostream os{internalBufs, 4096};
os << std::span<const uint8_t>{header, headerSize};
// generate masking key
static std::random_device rd;
static std::default_random_engine gen{rd()};
@@ -669,13 +675,23 @@ static void WriteFrame(WebSocketWriteReq& req,
}
}
bufs.append(internalBufs.begin(), internalBufs.end());
req.m_internalBufs.append(internalBufs.begin(), internalBufs.end());
// don't send the user bufs as we copied their data
} else {
bufs.append(internalBufs.begin(), internalBufs.end());
// manage m_internalBufs to efficiently store header
if (req.m_internalBufs.empty() ||
(req.m_internalBufPos + headerSize) > 4096) {
req.m_internalBufs.emplace_back(uv::Buffer::Allocate(4096));
req.m_internalBufPos = 0;
}
char* internalBuf =
req.m_internalBufs.back().data().data() + req.m_internalBufPos;
std::memcpy(internalBuf, header, headerSize);
bufs.emplace_back(internalBuf, headerSize);
req.m_internalBufPos += headerSize;
// servers can just send the buffers directly without masking
bufs.append(data.begin(), data.end());
}
req.m_internalBufs.append(internalBufs.begin(), internalBufs.end());
req.m_userBufs.append(data.begin(), data.end());
}