size_t qfind_first_byte_of_sse42(const StringPieceLite haystack,
const StringPieceLite needles) {
if (UNLIKELY(needles.empty() || haystack.empty())) {
return std::string::npos;
} else if (needles.size() <= 16) {
// we can save some unnecessary load instructions by optimizing for
// the common case of needles.size() <= 16
return qfind_first_byte_of_needles16(haystack, needles);
}
if (haystack.size() < 16 &&
page_for(haystack.end() - 1) != page_for(haystack.data() + 16)) {
// We can't safely SSE-load haystack. Use a different approach.
if (haystack.size() <= 2) {
return qfind_first_byte_of_std(haystack, needles);
}
return qfind_first_byte_of_byteset(haystack, needles);
}
auto ret = scanHaystackBlock<false>(haystack, needles, 0);
if (ret != std::string::npos) {
return ret;
}
size_t i = nextAlignedIndex(haystack.data());
for (; i < haystack.size(); i += 16) {
ret = scanHaystackBlock<true>(haystack, needles, i);
if (ret != std::string::npos) {
return ret;
}
}
return std::string::npos;
}
