ClickHouse/dbms/Functions/LowerUpperImpl.h

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#include <Columns/ColumnString.h>
namespace DB
{
template <char not_case_lower_bound, char not_case_upper_bound>
struct LowerUpperImpl
{
static void vector(const ColumnString::Chars & data,
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const ColumnString::Offsets & offsets,
ColumnString::Chars & res_data,
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ColumnString::Offsets & res_offsets)
{
res_data.resize(data.size());
res_offsets.assign(offsets);
array(data.data(), data.data() + data.size(), res_data.data());
}
static void vectorFixed(const ColumnString::Chars & data, size_t /*n*/, ColumnString::Chars & res_data)
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{
res_data.resize(data.size());
array(data.data(), data.data() + data.size(), res_data.data());
}
private:
static void array(const UInt8 * src, const UInt8 * src_end, UInt8 * dst)
{
const auto flip_case_mask = 'A' ^ 'a';
#ifdef __SSE2__
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const auto bytes_sse = sizeof(__m128i);
const auto src_end_sse = src_end - (src_end - src) % bytes_sse;
const auto v_not_case_lower_bound = _mm_set1_epi8(not_case_lower_bound - 1);
const auto v_not_case_upper_bound = _mm_set1_epi8(not_case_upper_bound + 1);
const auto v_flip_case_mask = _mm_set1_epi8(flip_case_mask);
for (; src < src_end_sse; src += bytes_sse, dst += bytes_sse)
{
/// load 16 sequential 8-bit characters
const auto chars = _mm_loadu_si128(reinterpret_cast<const __m128i *>(src));
/// find which 8-bit sequences belong to range [case_lower_bound, case_upper_bound]
const auto is_not_case
= _mm_and_si128(_mm_cmpgt_epi8(chars, v_not_case_lower_bound), _mm_cmplt_epi8(chars, v_not_case_upper_bound));
/// keep `flip_case_mask` only where necessary, zero out elsewhere
const auto xor_mask = _mm_and_si128(v_flip_case_mask, is_not_case);
/// flip case by applying calculated mask
const auto cased_chars = _mm_xor_si128(chars, xor_mask);
/// store result back to destination
_mm_storeu_si128(reinterpret_cast<__m128i *>(dst), cased_chars);
}
#endif
for (; src < src_end; ++src, ++dst)
if (*src >= not_case_lower_bound && *src <= not_case_upper_bound)
*dst = *src ^ flip_case_mask;
else
*dst = *src;
}
};
}