Optimization of websocket masking

[tsctx]

as titled

This is a cause of poor performance.

undici/lib/web/websocket/frame.js

Lines 85 to 88 in 0980f9d

	// mask body
	for (let i = 0; i < bodyLength; ++i) {
	buffer[offset + i] = frameData[i] ^ maskKey[i & 3]
	}

[Uzlopak]

Well. we could reduce the for loop overhead by doing 4 masking operations instead of one.

[ronag]

As I indicated earlier. The masking is as far as I know totally useless for backend and could just be skipped...

[Uzlopak]

Maybe instead of i + 4 < length, you precalculate that too

const lengthFor4 = length - (length & 3)

[Uzlopak]

maybe for the last potential 3 operations a duffs device?

[tsctx]

yes?

[Uzlopak]

Something like this. Sry, I still suffer from a heat stroke and cant provide better code.

switch (length & 3) {
  case 3:
    buffer[i + 3] ^ mask[3]
  case 2:
    buffer[i + 2] ^ mask[2]
  case 2:
    buffer[i + 1] ^ mask[1]
  ...

[tsctx]

Take care and get well soon.

[tsctx]

I give this up