Optimize parseNal

[longnguyen2004]

Profiling the library showed that parseNal is very inefficient. It was performing an O(n^2) search for the NAL start prefix code, and also doing a lot of allocations in the for loop. All of that in a very hot code path leads to poor performance.

I rewritten the function to use indexOf, and get rid of the O(n^2) loop along with the excessive allocation from the subarray() call.

Before

Statistical profiling result from isolate-0x5c006f0-186514-v8.log, (47617 ticks, 29409 unaccounted, 0 excluded).

 [Shared libraries]:
   ticks  total  nonlib   name
    558    1.2%          /usr/lib/x86_64-linux-gnu/libc.so.6
     31    0.1%          /home/hp/.local/bin/node
     27    0.1%          /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
      9    0.0%          [vdso]

 [JavaScript]:
   ticks  total  nonlib   name
   4265    9.0%    9.1%  JS: *parseNal /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/dist/media/H264NalSplitter.js:60:13
    342    0.7%    0.7%  JS: *wasm-function[48]
    132    0.3%    0.3%  JS: *wasm-function[112]
    105    0.2%    0.2%  JS: *wasm-function[62]
     78    0.2%    0.2%  JS: *sendFrame /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/dist/client/packet/VideoPacketizerH264.js:61:14
     72    0.2%    0.2%  JS: *Qr /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/node_modules/.pnpm/[email protected]/node_modules/libsodium-wrappers/dist/modules/libsodium-wrappers.js:1:79348
     70    0.1%    0.1%  JS: *concat node:buffer:576:32
     44    0.1%    0.1%  JS: *Socket.send node:dgram:576:33
     35    0.1%    0.1%  JS: *doSend node:dgram:677:16

--- lots of lines omitted for brevity ---

[Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 1.0% are not shown.

   ticks parent  name
  29409   61.8%  UNKNOWN
  19959   67.9%    JS: *parseNal /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/dist/media/H264NalSplitter.js:60:13
  18250   91.4%      JS: *_transform /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/dist/media/H264NalSplitter.js:103:15
  17508   95.9%        JS: ^Transform._write node:internal/streams/transform:170:38
  17031   97.3%          JS: *ondata node:internal/streams/readable:783:18
  15735   92.4%            JS: *Readable.read node:internal/streams/readable:421:35

After

Statistical profiling result from isolate-0x6f926f0-187287-v8.log, (56686 ticks, 10312 unaccounted, 0 excluded).

 [Shared libraries]:
   ticks  total  nonlib   name
    889    1.6%          /usr/lib/x86_64-linux-gnu/libc.so.6
     33    0.1%          /home/hp/.local/bin/node
     22    0.0%          /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
     19    0.0%          [vdso]

 [JavaScript]:
   ticks  total  nonlib   name
    927    1.6%    1.7%  JS: *wasm-function[48]
    381    0.7%    0.7%  JS: *wasm-function[112]
    249    0.4%    0.4%  JS: *wasm-function[62]
    183    0.3%    0.3%  JS: *sendFrame /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/dist/client/packet/VideoPacketizerH264.js:61:14
    167    0.3%    0.3%  JS: *concat node:buffer:576:32
    166    0.3%    0.3%  JS: *Qr /home/hp/DiscordFFmpegRelay/node_modules/.pnpm/github.com+longnguyen2004+discord-video-stream@dc8d74761cfdb6c3747f6b126375e502bb26a4f2_discord.js-selfbot-v13@3.0.2/node_modules/@dank074/discord-video-stream/node_modules/.pnpm/[email protected]/node_modules/libsodium-wrappers/dist/modules/libsodium-wrappers.js:1:79348
    106    0.2%    0.2%  JS: *Socket.send node:dgram:576:33

--- lots of lines omitted for brevity ---

[Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 1.0% are not shown.

   ticks parent  name
  38846   68.5%  epoll_pwait@@GLIBC_2.6

  10312   18.2%  UNKNOWN
   1519   14.7%    JS: *doSend node:dgram:677:16
   1519  100.0%      JS: *afterDns node:dgram:662:20
   1519  100.0%        JS: *processTicksAndRejections node:internal/process/task_queues:67:35
     27    1.8%          JS: ^runNextTicks node:internal/process/task_queues:58:22
     27  100.0%            JS: *processTimers node:internal/timers:499:25
    754    7.3%    JS: *lookup node:dns:140:16
    754  100.0%      JS: *Socket.send node:dgram:576:33

cc @aiko-chan-ai

[longnguyen2004]

rbsp() also looks like a prime candidate for optimization, but it's not that big of a problem compared to parseNal()

[dank074]

Good work