src: use stack allocation in indexOf latin1 path#62268
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src: use stack allocation in indexOf latin1 path#62268mertcanaltin wants to merge 1 commit intonodejs:mainfrom
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #62268 +/- ##
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+ Coverage 89.67% 89.69% +0.01%
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Files 676 676
Lines 206555 206552 -3
Branches 39552 39559 +7
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+ Hits 185225 185258 +33
+ Misses 13448 13438 -10
+ Partials 7882 7856 -26
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addaleax
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Mar 15, 2026
anonrig
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Mar 16, 2026
Flarna
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lemire
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Mar 16, 2026
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Replaced malloc / free with MaybeStackBuffer in the Latin1 path of IndexOfString.
For short needles, the allocation stays on the stack, avoiding heap allocation.
This results in a 12-15% improvement for short string searches.
➜ node git:(mert/buffer-indexof-stack-alloc) ✗ node-benchmark-compare ./result.csv confidence improvement accuracy (*) (**) (***) buffers/buffer-indexof-number.js n=1000000 value=64 * 1.55 % ±1.36% ±1.87% ±2.57% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='--l' 0.27 % ±1.13% ±1.57% ±2.17% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='@' 1.72 % ±2.49% ±3.42% ±4.68% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='</i> to the Caterpillar' 0.09 % ±0.31% ±0.43% ±0.59% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='aaaaaaaaaaaaaaaaa' 5.67 % ±12.05% ±17.30% ±25.40% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='Alice' -0.13 % ±2.35% ±3.23% ±4.41% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='found it very' -0.01 % ±0.55% ±0.76% ±1.04% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='Gryphon' -0.56 % ±1.41% ±1.95% ±2.70% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='neighbouring pool' 10.17 % ±24.08% ±34.59% ±50.85% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='Ou est ma chatte?' -0.04 % ±0.53% ±0.73% ±0.99% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='SQ' * 1.19 % ±1.18% ±1.62% ±2.24% buffers/buffer-indexof.js n=50000 type='buffer' encoding='undefined' search='venture to go near the house till she had brought herself down to' 0.22 % ±0.72% ±0.99% ±1.34% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='--l' * 1.76 % ±1.42% ±2.01% ±2.86% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='@' *** 12.51 % ±1.72% ±2.36% ±3.23% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='</i> to the Caterpillar' -0.01 % ±0.32% ±0.44% ±0.60% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='aaaaaaaaaaaaaaaaa' -0.65 % ±2.15% ±2.98% ±4.14% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='Alice' *** 15.69 % ±2.20% ±3.02% ±4.13% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='found it very' -0.02 % ±0.97% ±1.39% ±2.02% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='Gryphon' * 1.90 % ±1.71% ±2.35% ±3.21% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='neighbouring pool' -0.01 % ±0.58% ±0.80% ±1.11% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='Ou est ma chatte?' 0.05 % ±1.34% ±1.89% ±2.71% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='SQ' * 1.46 % ±1.37% ±1.89% ±2.57% buffers/buffer-indexof.js n=50000 type='string' encoding='latin1' search='venture to go near the house till she had brought herself down to' -0.06 % ±0.75% ±1.07% ±1.52% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='--l' -0.09 % ±1.19% ±1.63% ±2.23% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='@' 0.28 % ±1.60% ±2.23% ±3.15% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='</i> to the Caterpillar' 0.25 % ±0.33% ±0.46% ±0.65% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='aaaaaaaaaaaaaaaaa' 0.57 % ±2.04% ±2.83% ±3.95% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='Alice' 1.94 % ±2.44% ±3.35% ±4.57% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='found it very' -0.38 % ±0.92% ±1.29% ±1.84% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='Gryphon' -0.34 % ±1.35% ±1.85% ±2.53% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='neighbouring pool' 0.08 % ±0.36% ±0.50% ±0.70% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='Ou est ma chatte?' 0.58 % ±0.79% ±1.11% ±1.55% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='SQ' -0.16 % ±1.32% ±1.83% ±2.51% buffers/buffer-indexof.js n=50000 type='string' encoding='ucs2' search='venture to go near the house till she had brought herself down to' -0.12 % ±0.97% ±1.33% ±1.83% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='--l' -0.96 % ±1.28% ±1.75% ±2.39% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='@' -0.20 % ±1.83% ±2.53% ±3.47% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='</i> to the Caterpillar' -0.13 % ±0.40% ±0.55% ±0.76% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='aaaaaaaaaaaaaaaaa' -1.16 % ±1.51% ±2.07% ±2.83% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='Alice' 0.37 % ±2.71% ±3.74% ±5.18% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='found it very' -0.17 % ±1.09% ±1.50% ±2.04% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='Gryphon' -0.22 % ±1.46% ±2.01% ±2.77% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='neighbouring pool' -0.06 % ±0.37% ±0.51% ±0.69% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='Ou est ma chatte?' 1.16 % ±1.86% ±2.65% ±3.85% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='SQ' 1.60 % ±2.32% ±3.25% ±4.62% buffers/buffer-indexof.js n=50000 type='string' encoding='utf8' search='venture to go near the house till she had brought herself down to' -0.64 % ±0.78% ±1.09% ±1.53% Be aware that when doing many comparisons the risk of a false-positive result increases. In this case, there are 45 comparisons, you can thus expect the following amount of false-positive results: 2.25 false positives, when considering a 5% risk acceptance (*, **, ***), 0.45 false positives, when considering a 1% risk acceptance (**, ***), 0.04 false positives, when considering a 0.1% risk acceptance (***) ➜ node git:(mert/buffer-indexof-stack-alloc) ✗