buffer: improve btoa performance

[anonrig]

Improves the performance of the legacy btoa function. It's not recommended to be used in production.

                                            confidence improvement accuracy (*)    (**)   (***)
buffers/buffer-btoa.js n=1000000 size=1024        ***   1089.00 %      ±15.27% ±20.57% ±27.29%
buffers/buffer-btoa.js n=1000000 size=128         ***    571.99 %       ±6.85%  ±9.22% ±12.22%
buffers/buffer-btoa.js n=1000000 size=16          ***    306.04 %       ±4.24%  ±5.70%  ±7.53%
buffers/buffer-btoa.js n=1000000 size=256         ***    870.77 %      ±13.85% ±18.67% ±24.78%
buffers/buffer-btoa.js n=1000000 size=32          ***    350.58 %       ±4.61%  ±6.18%  ±8.15%
buffers/buffer-btoa.js n=1000000 size=64          ***    462.57 %       ±5.60%  ±7.51%  ±9.91%

Disclaimer

"btoa" is a legacy functionality, and not recommended to be used in production applications.

Thanks Matthieu Riegler for the poster

[lemire]

@anonrig I recommend trying something like this... We have three cases: one external one-byte string (easy), one non-external one byte string (we use WriteOneByte) and the general case where we go to 16-bit words, we try converting to latin1 and then we see what happens. In this scenario, there might be an error condition, currently in the code I suggest, it returns the empty string.

static void Btoa(const FunctionCallbackInfo<Value>& args) {
  CHECK_EQ(args.Length(), 1);
  Environment* env = Environment::GetCurrent(args);
  THROW_AND_RETURN_IF_NOT_STRING(env, args[0], "argument");

  Local<String> input = args[0].As<String>();
  MaybeStackBuffer<char> buffer;
  size_t written;

  if (input->IsExternalOneByte()) {  // 8-bit case
    auto ext = input->GetExternalOneByteStringResource();
    size_t expected_length = simdutf::base64_length_from_binary(ext->length());
    buffer.AllocateSufficientStorage(expected_length + 1);
    buffer.SetLengthAndZeroTerminate(expected_length);
    written = simdutf::binary_to_base64(
        ext->data(), ext->length(), buffer.out(), simdutf::base64_default);
  } if(input->IsOneByte()) {
    MaybeStackBuffer<uint8_t> stack_buf(input->Length());
        input->WriteOneByte(env->isolate(),
                           stack_buf.out(),
                           0,
                           input->Length(),
                           String::NO_NULL_TERMINATION);

    size_t expected_length = simdutf::base64_length_from_binary(input->Length());
    buffer.AllocateSufficientStorage(expected_length + 1);
    buffer.SetLengthAndZeroTerminate(expected_length);
    written = simdutf::binary_to_base64(
        reinterpret_cast<const char*>(*stack_buf), input->Length(), buffer.out());
  } else {
    String::Value value(env->isolate(), input);
    MaybeStackBuffer<char> stack_buf(value.length());
    size_t out_len = simdutf::convert_utf16_to_latin1(reinterpret_cast<const char16_t *>(*value), value.length(), stack_buf.out());
    if(out_len == 0) { // error
      return args.GetReturnValue().SetEmptyString();
    }
    size_t expected_length = simdutf::base64_length_from_binary(out_len);
    buffer.AllocateSufficientStorage(expected_length + 1);
    buffer.SetLengthAndZeroTerminate(expected_length);
    written = simdutf::binary_to_base64(
        *stack_buf, out_len, buffer.out());
  }

  auto value =
      String::NewFromOneByte(env->isolate(),
                             reinterpret_cast<const uint8_t*>(buffer.out()),
                             NewStringType::kNormal,
                             written)
          .ToLocalChecked();
  return args.GetReturnValue().Set(value);
}

This should be considered ChatGTP-quality code: I did not even try to test it... It is only as an idea.

[lemire]

@anonrig Lint. Lint. Lint.

[anonrig]

@lemire I've updated the benchmark results as well :-)

[lemire]

@anonrig My proposed code would return the empty string on error, but we need to throw, I pushed a commit that does that. (Very minor change.)

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/58249/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/58258/

[nodejs-github-bot]

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----------------------------------- PR info ------------------------------------
Title      buffer: improve `btoa` performance (#52427)
Author     Yagiz Nizipli  (@anonrig)
Branch     anonrig:improve-btoa -> nodejs:main
Labels     buffer, c++, needs-ci
Commits    2
 - buffer: improve `btoa` performance
 - fix: return exception
Committers 2
 - Yagiz Nizipli 
 - Daniel Lemire 
PR-URL: https://github.com/nodejs/node/pull/52427
Reviewed-By: Daniel Lemire 
Reviewed-By: James M Snell 
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/52427
Reviewed-By: Daniel Lemire 
Reviewed-By: James M Snell 
--------------------------------------------------------------------------------
   ℹ  This PR was created on Mon, 08 Apr 2024 17:24:56 GMT
   ✔  Approvals: 2
   ✔  - Daniel Lemire (@lemire): https://github.com/nodejs/node/pull/52427#pullrequestreview-1992265694
   ✔  - James M Snell (@jasnell) (TSC): https://github.com/nodejs/node/pull/52427#pullrequestreview-1993089038
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[main 50c914c521] buffer: improve `btoa` performance
 Author: Yagiz Nizipli 
 Date: Mon Apr 8 13:23:56 2024 -0400
 3 files changed, 81 insertions(+), 7 deletions(-)
 create mode 100644 benchmark/buffers/buffer-btoa.js
[main de7c8dcb6a] fix: return exception
 Author: Daniel Lemire 
 Date: Wed Apr 10 09:44:11 2024 -0400
 2 files changed, 6 insertions(+), 2 deletions(-)
   ✔  Patches applied
There are 2 commits in the PR. Attempting autorebase.
Rebasing (2/4)
Executing: git node land --amend --yes

--------------------------------- New Message ----------------------------------

buffer: improve btoa performance
PR-URL: #52427

Reviewed-By: Daniel Lemire daniel@lemire.me

Reviewed-By: James M Snell jasnell@gmail.com
[detached HEAD f1e7db2933] buffer: improve btoa performance

Author: Yagiz Nizipli yagiz@nizipli.com

Date: Mon Apr 8 13:23:56 2024 -0400

3 files changed, 81 insertions(+), 7 deletions(-)

create mode 100644 benchmark/buffers/buffer-btoa.js

Rebasing (3/4)

Rebasing (4/4)
Executing: git node land --amend --yes

--------------------------------- New Message ----------------------------------

fix: return exception
PR-URL: #52427

Reviewed-By: Daniel Lemire daniel@lemire.me

Reviewed-By: James M Snell jasnell@gmail.com
[detached HEAD a285a09324] fix: return exception

Author: Daniel Lemire dlemire@lemire.me

Date: Wed Apr 10 09:44:11 2024 -0400

2 files changed, 6 insertions(+), 2 deletions(-)
Successfully rebased and updated refs/heads/main.
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https://github.com/nodejs/node/actions/runs/8645651485

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