src: skip duplicate UTF-8 validation in TextDecoder fatal path by mertcanaltin · Pull Request #63231 · nodejs/node

mertcanaltin · 2026-05-10T20:53:03Z

In TextDecoder's strict mode, the utf-8 buffer was being validated twice, I removed the second validation, non-asci decoding in strict mode is now 27–34% faster

Bench results (verry long, I wrote a gist file):

https://gist.github.com/mertcanaltin/42f2fe0808e85741bcc76e7f59a4229e

Short results:

util/text-decoder.js fatal=1 encoding='utf-8' content='one-byte-string'
  len=131072 ArrayBuffer       +31.14% ±1.90%
  len=131072 Buffer            +32.05% ±1.31%
  len=131072 SharedArrayBuffer +31.54% ±0.75%
  len=16384  ArrayBuffer       +28.06% ±1.73%
  len=16384  Buffer            +27.49% ±2.92%
  len=16384  SharedArrayBuffer +28.03% ±1.77%

util/text-decoder.js fatal=1 encoding='utf-8' content='two-byte-string'
  len=131072 ArrayBuffer       +33.67% ±1.17%
  len=131072 Buffer            +34.15% ±1.73%
  len=131072 SharedArrayBuffer +34.03% ±1.12%
  len=16384  ArrayBuffer       +31.13% ±1.71%
  len=16384  Buffer            +29.02% ±1.73%
  len=16384  SharedArrayBuffer +28.34% ±2.12%

util/text-decoder-stream.js unicode=1 fatal=1 encoding='utf-8'
  len=131072 Buffer            +11.66%
  len=131072 SharedArrayBuffer  +9.36%
  len=16384  Buffer             +8.08%
  len=16384  SharedArrayBuffer  +6.65%

nodejs-github-bot · 2026-05-10T20:53:08Z

Review requested:

@nodejs/performance

Signed-off-by: Mert Can Altin <[email protected]>

codecov · 2026-05-10T22:25:52Z

Codecov Report

❌ Patch coverage is 29.62963% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.03%. Comparing base (facd71e) to head (0df76ab).
⚠️ Report is 195 commits behind head on main.

Files with missing lines	Patch %	Lines
src/string_bytes.cc	25.00%	13 Missing and 5 partials ⚠️
src/encoding_binding.cc	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63231      +/-   ##
==========================================
- Coverage   90.04%   90.03%   -0.01%     
==========================================
  Files         713      713              
  Lines      224950   224976      +26     
  Branches    42530    42542      +12     
==========================================
+ Hits       202548   202554       +6     
- Misses      14188    14191       +3     
- Partials     8214     8231      +17

Files with missing lines	Coverage Δ
src/string_bytes.h	`80.00% <ø> (ø)`
src/encoding_binding.cc	`53.22% <66.66%> (+0.30%)`	⬆️
src/string_bytes.cc	`71.34% <25.00%> (-3.29%)`	⬇️

... and 34 files with indirect coverage changes

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gurgunday · 2026-05-13T20:32:35Z

Cc @ChALkeR if you want to take a look

mcollina

RSLGTM

nodejs-github-bot · 2026-05-16T07:20:12Z

CI: https://ci.nodejs.org/job/node-test-pull-request/73489/

nodejs-github-bot · 2026-05-26T13:40:30Z

Commit Queue failed

- Loading data for nodejs/node/pull/63231
✔  Done loading data for nodejs/node/pull/63231
----------------------------------- PR info ------------------------------------
Title      src: skip duplicate UTF-8 validation in TextDecoder fatal path (#63231)
Author     Mert Can Altin <[email protected]> (@mertcanaltin)
Branch     mertcanaltin:mert/textdecoder-skip-utf8-revalidation -> nodejs:main
Labels     c++, lib / src, author ready, needs-ci
Commits    2
 - src: skip duplicate UTF-8 validation in TextDecoder fatal path
 - lint
Committers 1
 - Mert Can Altin <[email protected]>
PR-URL: https://github.com/nodejs/node/pull/63231
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Gürgün Dayıoğlu <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/63231
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Gürgün Dayıoğlu <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Sun, 10 May 2026 20:53:03 GMT
   ✔  Approvals: 4
   ✔  - Yagiz Nizipli (@anonrig) (TSC): https://github.com/nodejs/node/pull/63231#pullrequestreview-4260222797
   ✔  - Anna Henningsen (@addaleax): https://github.com/nodejs/node/pull/63231#pullrequestreview-4283284001
   ✔  - Gürgün Dayıoğlu (@gurgunday): https://github.com/nodejs/node/pull/63231#pullrequestreview-4285127669
   ✔  - Matteo Collina (@mcollina) (TSC): https://github.com/nodejs/node/pull/63231#pullrequestreview-4303274342
   ✘  1 GitHub CI job(s) failed:
   ✘    - test-linux (ubuntu-24.04-arm): FAILURE (https://github.com/nodejs/node/actions/runs/25639658919/job/75257778560)
   ℹ  Last Full PR CI on 2026-05-16T07:20:12Z: https://ci.nodejs.org/job/node-test-pull-request/73489/
- Querying data for job/node-test-pull-request/73489/
✔  Build data downloaded
   ✔  Last Jenkins CI successful
--------------------------------------------------------------------------------
   ✔  Aborted `git node land` session in /home/runner/work/node/node/.ncu

https://github.com/nodejs/node/actions/runs/26451423810

Signed-off-by: Mert Can Altin <[email protected]> PR-URL: #63231 Reviewed-By: Yagiz Nizipli <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Gürgün Dayıoğlu <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

addaleax · 2026-05-27T19:31:55Z

Landed in 4639dcb

Signed-off-by: Mert Can Altin <[email protected]> PR-URL: #63231 Reviewed-By: Yagiz Nizipli <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Gürgün Dayıoğlu <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels May 10, 2026

src: skip duplicate UTF-8 validation in TextDecoder fatal path

25fe9af

Signed-off-by: Mert Can Altin <[email protected]>

mertcanaltin force-pushed the mert/textdecoder-skip-utf8-revalidation branch from 1ea0c09 to 25fe9af Compare May 10, 2026 20:55

lint

0df76ab

anonrig approved these changes May 11, 2026

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addaleax approved these changes May 13, 2026

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mertcanaltin mentioned this pull request May 27, 2026

src: remove double encoding validation on fatal path #63587

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