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297 lines
10 KiB
C++
297 lines
10 KiB
C++
#pragma once
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#include <cstdint>
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#include <string>
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#if defined(__SSE2__)
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#include <emmintrin.h>
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#endif
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#if defined(__SSE4_2__)
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#include <nmmintrin.h>
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#endif
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/** find_first_symbols<c1, c2, ...>(begin, end):
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*
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* Allow to search for next character from the set of 'symbols...' in a string.
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* It is similar to 'strpbrk', 'strcspn' (and 'strchr', 'memchr' in the case of one symbol and '\0'),
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* but with the following differences:
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* - works with any memory ranges, including containing zero bytes;
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* - doesn't require terminating zero byte: end of memory range is passed explicitly;
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* - if not found, returns pointer to end instead of nullptr;
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* - maximum number of symbols to search is 16.
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*
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* Uses SSE 2 in case of small number of symbols for search and SSE 4.2 in the case of large number of symbols,
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* that have more than 2x performance advantage over trivial loop
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* in the case of parsing tab-separated dump with (probably escaped) string fields.
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* In the case of parsing tab separated dump with short strings, there is no performance degradation over trivial loop.
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*
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* Note: the optimal threshold to choose between SSE 2 and SSE 4.2 may depend on CPU model.
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*
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* find_last_symbols_or_null<c1, c2, ...>(begin, end):
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*
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* Allow to search for the last matching character in a string.
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* If no such characters, returns nullptr.
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*/
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namespace detail
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{
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template <char ...chars> constexpr bool is_in(char x) { return ((x == chars) || ...); }
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#if defined(__SSE2__)
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template <char s0>
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inline __m128i mm_is_in(__m128i bytes)
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{
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__m128i eq0 = _mm_cmpeq_epi8(bytes, _mm_set1_epi8(s0));
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return eq0;
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}
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template <char s0, char s1, char... tail>
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inline __m128i mm_is_in(__m128i bytes)
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{
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__m128i eq0 = _mm_cmpeq_epi8(bytes, _mm_set1_epi8(s0));
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__m128i eq = mm_is_in<s1, tail...>(bytes);
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return _mm_or_si128(eq0, eq);
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}
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#endif
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template <bool positive>
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constexpr bool maybe_negate(bool x) { return x == positive; }
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template <bool positive>
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constexpr uint16_t maybe_negate(uint16_t x)
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{
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if constexpr (positive)
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return x;
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else
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return ~x;
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}
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enum class ReturnMode
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{
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End,
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Nullptr,
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};
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template <bool positive, ReturnMode return_mode, char... symbols>
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inline const char * find_first_symbols_sse2(const char * const begin, const char * const end)
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{
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const char * pos = begin;
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#if defined(__SSE2__)
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for (; pos + 15 < end; pos += 16)
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(pos));
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__m128i eq = mm_is_in<symbols...>(bytes);
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uint16_t bit_mask = maybe_negate<positive>(uint16_t(_mm_movemask_epi8(eq)));
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if (bit_mask)
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return pos + __builtin_ctz(bit_mask);
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}
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#endif
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for (; pos < end; ++pos)
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if (maybe_negate<positive>(is_in<symbols...>(*pos)))
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return pos;
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return return_mode == ReturnMode::End ? end : nullptr;
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}
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template <bool positive, ReturnMode return_mode, char... symbols>
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inline const char * find_last_symbols_sse2(const char * const begin, const char * const end)
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{
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const char * pos = end;
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#if defined(__SSE2__)
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for (; pos - 16 >= begin; pos -= 16) /// Assuming the pointer cannot overflow. Assuming we can compare these pointers.
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(pos - 16));
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__m128i eq = mm_is_in<symbols...>(bytes);
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uint16_t bit_mask = maybe_negate<positive>(uint16_t(_mm_movemask_epi8(eq)));
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if (bit_mask)
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return pos - 1 - (__builtin_clz(bit_mask) - 16); /// because __builtin_clz works with mask as uint32.
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}
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#endif
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--pos;
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for (; pos >= begin; --pos)
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if (maybe_negate<positive>(is_in<symbols...>(*pos)))
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return pos;
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return return_mode == ReturnMode::End ? end : nullptr;
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}
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template <bool positive, ReturnMode return_mode, size_t num_chars,
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char c01, char c02 = 0, char c03 = 0, char c04 = 0,
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char c05 = 0, char c06 = 0, char c07 = 0, char c08 = 0,
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char c09 = 0, char c10 = 0, char c11 = 0, char c12 = 0,
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char c13 = 0, char c14 = 0, char c15 = 0, char c16 = 0>
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inline const char * find_first_symbols_sse42(const char * const begin, const char * const end)
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{
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const char * pos = begin;
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#if defined(__SSE4_2__)
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constexpr int mode = _SIDD_UBYTE_OPS | _SIDD_CMP_EQUAL_ANY | _SIDD_LEAST_SIGNIFICANT;
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__m128i set = _mm_setr_epi8(c01, c02, c03, c04, c05, c06, c07, c08, c09, c10, c11, c12, c13, c14, c15, c16);
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for (; pos + 15 < end; pos += 16)
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{
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__m128i bytes = _mm_loadu_si128(reinterpret_cast<const __m128i *>(pos));
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if constexpr (positive)
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{
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if (_mm_cmpestrc(set, num_chars, bytes, 16, mode))
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return pos + _mm_cmpestri(set, num_chars, bytes, 16, mode);
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}
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else
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{
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if (_mm_cmpestrc(set, num_chars, bytes, 16, mode | _SIDD_NEGATIVE_POLARITY))
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return pos + _mm_cmpestri(set, num_chars, bytes, 16, mode | _SIDD_NEGATIVE_POLARITY);
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}
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}
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#endif
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for (; pos < end; ++pos)
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if ( (num_chars >= 1 && maybe_negate<positive>(*pos == c01))
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|| (num_chars >= 2 && maybe_negate<positive>(*pos == c02))
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|| (num_chars >= 3 && maybe_negate<positive>(*pos == c03))
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|| (num_chars >= 4 && maybe_negate<positive>(*pos == c04))
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|| (num_chars >= 5 && maybe_negate<positive>(*pos == c05))
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|| (num_chars >= 6 && maybe_negate<positive>(*pos == c06))
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|| (num_chars >= 7 && maybe_negate<positive>(*pos == c07))
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|| (num_chars >= 8 && maybe_negate<positive>(*pos == c08))
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|| (num_chars >= 9 && maybe_negate<positive>(*pos == c09))
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|| (num_chars >= 10 && maybe_negate<positive>(*pos == c10))
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|| (num_chars >= 11 && maybe_negate<positive>(*pos == c11))
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|| (num_chars >= 12 && maybe_negate<positive>(*pos == c12))
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|| (num_chars >= 13 && maybe_negate<positive>(*pos == c13))
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|| (num_chars >= 14 && maybe_negate<positive>(*pos == c14))
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|| (num_chars >= 15 && maybe_negate<positive>(*pos == c15))
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|| (num_chars >= 16 && maybe_negate<positive>(*pos == c16)))
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return pos;
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return return_mode == ReturnMode::End ? end : nullptr;
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}
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/// NOTE No SSE 4.2 implementation for find_last_symbols_or_null. Not worth to do.
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template <bool positive, ReturnMode return_mode, char... symbols>
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inline const char * find_first_symbols_dispatch(const char * begin, const char * end)
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requires(0 <= sizeof...(symbols) && sizeof...(symbols) <= 16)
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{
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#if defined(__SSE4_2__)
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if (sizeof...(symbols) >= 5)
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return find_first_symbols_sse42<positive, return_mode, sizeof...(symbols), symbols...>(begin, end);
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else
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#endif
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return find_first_symbols_sse2<positive, return_mode, symbols...>(begin, end);
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}
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}
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template <char... symbols>
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inline const char * find_first_symbols(const char * begin, const char * end)
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{
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return detail::find_first_symbols_dispatch<true, detail::ReturnMode::End, symbols...>(begin, end);
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}
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/// Returning non const result for non const arguments.
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/// It is convenient when you are using this function to iterate through non-const buffer.
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template <char... symbols>
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inline char * find_first_symbols(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_first_symbols_dispatch<true, detail::ReturnMode::End, symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_first_not_symbols(const char * begin, const char * end)
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{
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return detail::find_first_symbols_dispatch<false, detail::ReturnMode::End, symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_first_not_symbols(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_first_symbols_dispatch<false, detail::ReturnMode::End, symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_first_symbols_or_null(const char * begin, const char * end)
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{
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return detail::find_first_symbols_dispatch<true, detail::ReturnMode::Nullptr, symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_first_symbols_or_null(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_first_symbols_dispatch<true, detail::ReturnMode::Nullptr, symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_first_not_symbols_or_null(const char * begin, const char * end)
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{
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return detail::find_first_symbols_dispatch<false, detail::ReturnMode::Nullptr, symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_first_not_symbols_or_null(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_first_symbols_dispatch<false, detail::ReturnMode::Nullptr, symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_last_symbols_or_null(const char * begin, const char * end)
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{
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return detail::find_last_symbols_sse2<true, detail::ReturnMode::Nullptr, symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_last_symbols_or_null(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_last_symbols_sse2<true, detail::ReturnMode::Nullptr, symbols...>(begin, end));
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}
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template <char... symbols>
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inline const char * find_last_not_symbols_or_null(const char * begin, const char * end)
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{
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return detail::find_last_symbols_sse2<false, detail::ReturnMode::Nullptr, symbols...>(begin, end);
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}
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template <char... symbols>
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inline char * find_last_not_symbols_or_null(char * begin, char * end)
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{
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return const_cast<char *>(detail::find_last_symbols_sse2<false, detail::ReturnMode::Nullptr, symbols...>(begin, end));
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}
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/// Slightly resembles boost::split. The drawback of boost::split is that it fires a false positive in clang static analyzer.
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/// See https://github.com/boostorg/algorithm/issues/63
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/// And https://bugs.llvm.org/show_bug.cgi?id=41141
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template <char... symbols, typename To>
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inline void splitInto(To & to, const std::string & what, bool token_compress = false)
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{
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const char * pos = what.data();
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const char * end = pos + what.size();
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while (pos < end)
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{
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const char * delimiter_or_end = find_first_symbols<symbols...>(pos, end);
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if (!token_compress || pos < delimiter_or_end)
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to.emplace_back(pos, delimiter_or_end - pos);
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if (delimiter_or_end < end)
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pos = delimiter_or_end + 1;
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else
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pos = delimiter_or_end;
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}
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}
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