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src: improve StringBytes::Encode perf on UTF8 #61131

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Merged
nodejs-github-bot merged 2 commits into from
Jan 21, 2026
Merged

src: improve StringBytes::Encode perf on UTF8 #61131

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d4f0460
src: improve StringBytes::Encode perf on UTF8
ChALkeR Dec 19, 2025
62af4d3
src: do not use simdutf path on very short input
ChALkeR Jan 20, 2026
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2 changes: 2 additions & 0 deletions src/encoding_binding.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -379,6 +379,8 @@ void BindingData::DecodeUTF8(const FunctionCallbackInfo<Value>& args) {
return node::THROW_ERR_ENCODING_INVALID_ENCODED_DATA(
env->isolate(), "The encoded data was not valid for encoding utf-8");
}

// TODO(chalker): save on utf8 validity recheck in StringBytes::Encode()
}

if (length == 0) return args.GetReturnValue().SetEmptyString();
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18 changes: 18 additions & 0 deletions src/string_bytes.cc
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Expand Up @@ -539,6 +539,24 @@ MaybeLocal<Value> StringBytes::Encode(Isolate* isolate,
return ExternOneByteString::NewFromCopy(isolate, buf, buflen);
}

if (simdutf::validate_utf8(buf, buflen)) {
// We know that we are non-ASCII (and are unlikely Latin1), use 2-byte
// In the most likely case of valid UTF-8, we can use this fast impl
size_t u16size = simdutf::utf16_length_from_utf8(buf, buflen);
if (u16size > static_cast<size_t>(v8::String::kMaxLength)) {
isolate->ThrowException(ERR_STRING_TOO_LONG(isolate));
return MaybeLocal<Value>();
}
uint16_t* dst = node::UncheckedMalloc<uint16_t>(u16size);
if (u16size != 0 && dst == nullptr) {
THROW_ERR_MEMORY_ALLOCATION_FAILED(isolate);
return MaybeLocal<Value>();
}
size_t utf16len = simdutf::convert_valid_utf8_to_utf16(
buf, buflen, reinterpret_cast<char16_t*>(dst));
return ExternTwoByteString::New(isolate, dst, utf16len);
}

val =
String::NewFromUtf8(isolate, buf, v8::NewStringType::kNormal, buflen);
Local<String> str;
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