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feat(perf): Speed up direct copy path for decodeUtf16Le() #1041

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Merged
boorad merged 2 commits into from
May 12, 2026
Merged

feat(perf): Speed up direct copy path for decodeUtf16Le() #1041

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444c345
Optimize decodeUtf16Le() performance
wh201906 May 12, 2026
0bc43e1
Fix dst ptr
wh201906 May 12, 2026
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12 changes: 8 additions & 4 deletions packages/react-native-quick-crypto/cpp/utils/HybridUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -142,11 +142,12 @@ namespace {
}

size_t offset = result.size();
result.resize(offset + (num * 2)); // This fills the buffer with '\0'
result.reserve(offset + (num * 2)); // Allocate buffer conservatively

auto* dst = result.data() + offset;
if (isAscii) {
// Widen ASCII characters from char into char16_t
result.resize(offset + (num * 2)); // This fills the buffer with '\0'
auto* dst = result.data() + offset;
const auto* asciiSrc = reinterpret_cast<const char*>(data);
for (size_t i = 0; i < num; i++, dst += 2) {
*dst = asciiSrc[i];
Expand All @@ -155,13 +156,16 @@ namespace {
return;
}

const auto* utf16Src = reinterpret_cast<const char16_t*>(data);
if constexpr (kCanDirectCopyUtf16) {
// Fast&direct copy path
std::memcpy(dst, utf16Src, num * 2);
const auto* byteSrc = reinterpret_cast<const uint8_t*>(data);
result.insert(result.end(), byteSrc, byteSrc + num * 2);
return;
}
// Slow path for unexpected endianness/char16_t size
result.resize(offset + (num * 2));
const auto* utf16Src = reinterpret_cast<const char16_t*>(data);
auto* dst = result.data() + offset;
for (size_t i = 0; i < num; i++) {
const uint16_t codeUnit = static_cast<uint16_t>(utf16Src[i]);
dst[i * 2 + 0] = static_cast<uint8_t>(codeUnit & 0xFFu);
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