From ad985f322796d25ca85a0c1ab02d664c8a8ad57f Mon Sep 17 00:00:00 2001
From: Andrew Kaster <andrew@ladybird.org>
Date: Thu, 20 Feb 2025 04:16:23 -0700
Subject: [PATCH] LibWebSocket: Only call send() once on WebSocketImpl

The previous implementation would call send a half-dozen times
when sending each frame of WebSocket data. This is excessive,
especially since we need to allocate a new buffer for the payload
in order to mask it anyway. Let's just allocate one buffer up front,
and send all the completed data at the end of the method
---
 Libraries/LibWebSocket/WebSocket.cpp | 37 +++++++++++++++++-----------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/Libraries/LibWebSocket/WebSocket.cpp b/Libraries/LibWebSocket/WebSocket.cpp
index f1f484057d7..6d59aaf1a5e 100644
--- a/Libraries/LibWebSocket/WebSocket.cpp
+++ b/Libraries/LibWebSocket/WebSocket.cpp
@@ -534,8 +534,13 @@ void WebSocket::send_frame(WebSocket::OpCode op_code, ReadonlyBytes payload, boo
 {
     VERIFY(m_impl);
     VERIFY(m_state == WebSocket::InternalState::Open);
+
+    ByteBuffer buf = MUST(ByteBuffer::create_uninitialized(1 + 9 + 4 + payload.size()));
+    size_t offset = 0;
+
     u8 frame_head[1] = { (u8)((is_final ? 0x80 : 0x00) | ((u8)(op_code) & 0xf)) };
-    m_impl->send(ReadonlyBytes(frame_head, 1));
+    buf.overwrite(offset, frame_head, 1);
+    offset += 1;
     // Section 5.1 : a client MUST mask all frames that it sends to the server
     bool has_mask = true;
     // FIXME: If the payload has a size > size_t max on a 32-bit platform, we could
@@ -555,7 +560,8 @@ void WebSocket::send_frame(WebSocket::OpCode op_code, ReadonlyBytes payload, boo
                 (u8)((payload.size() >> 8) & 0xff),
                 (u8)((payload.size() >> 0) & 0xff),
             };
-            m_impl->send(ReadonlyBytes(payload_length, 9));
+            buf.overwrite(offset, payload_length, 9);
+            offset += 9;
         } else {
             u8 payload_length[9] = {
                 (u8)((has_mask ? 0x80 : 0x00) | 127),
@@ -568,7 +574,8 @@ void WebSocket::send_frame(WebSocket::OpCode op_code, ReadonlyBytes payload, boo
                 (u8)((payload.size() >> 8) & 0xff),
                 (u8)((payload.size() >> 0) & 0xff),
             };
-            m_impl->send(ReadonlyBytes(payload_length, 9));
+            buf.overwrite(offset, payload_length, 9);
+            offset += 9;
         }
     } else if (payload.size() >= 126) {
         // Send (the 'mask' flag + 126) + the 2-byte payload length
@@ -577,13 +584,15 @@ void WebSocket::send_frame(WebSocket::OpCode op_code, ReadonlyBytes payload, boo
             (u8)((payload.size() >> 8) & 0xff),
             (u8)((payload.size() >> 0) & 0xff),
         };
-        m_impl->send(ReadonlyBytes(payload_length, 3));
+        buf.overwrite(offset, payload_length, 3);
+        offset += 3;
     } else {
         // Send the mask flag + the payload in a single byte
         u8 payload_length[1] = {
             (u8)((has_mask ? 0x80 : 0x00) | (u8)(payload.size() & 0x7f)),
         };
-        m_impl->send(ReadonlyBytes(payload_length, 1));
+        buf.overwrite(offset, payload_length, 1);
+        offset += 1;
     }
     if (has_mask) {
         // Section 10.3 :
@@ -591,22 +600,22 @@ void WebSocket::send_frame(WebSocket::OpCode op_code, ReadonlyBytes payload, boo
         // > that cannot be predicted by end applications that provide data
         u8 masking_key[4];
         Crypto::fill_with_secure_random(masking_key);
-        m_impl->send(ReadonlyBytes(masking_key, 4));
+        buf.overwrite(offset, masking_key, 4);
+        offset += 4;
         // don't try to send empty payload
         if (payload.size() == 0)
             return;
         // Mask the payload
-        auto buffer_result = ByteBuffer::create_uninitialized(payload.size());
-        if (!buffer_result.is_error()) {
-            auto& masked_payload = buffer_result.value();
-            for (size_t i = 0; i < payload.size(); ++i) {
-                masked_payload[i] = payload[i] ^ (masking_key[i % 4]);
-            }
-            m_impl->send(masked_payload);
+        auto masked_payload = buf.span().slice(offset, payload.size());
+        for (size_t i = 0; i < payload.size(); ++i) {
+            masked_payload[i] = payload[i] ^ (masking_key[i % 4]);
         }
+        offset += payload.size();
     } else if (payload.size() > 0) {
-        m_impl->send(payload);
+        buf.overwrite(offset, payload.data(), payload.size());
+        offset += payload.size();
     }
+    m_impl->send(buf.span().slice(0, offset));
 }
 
 void WebSocket::fatal_error(WebSocket::Error error)