ClickHouse/dbms/include/DB/Core/StringRef.h

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#pragma once
#include <string.h>
#include <city.h>
#include <string>
#include <vector>
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#include <functional>
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#include <ostream>
#if defined(__x86_64__)
#include <emmintrin.h>
#endif
/// Штука, чтобы не создавать строки для поиска подстроки в хэш таблице.
struct StringRef
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{
const char * data = nullptr;
size_t size = 0;
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StringRef(const char * data_, size_t size_) : data(data_), size(size_) {}
StringRef(const unsigned char * data_, size_t size_) : data(reinterpret_cast<const char *>(data_)), size(size_) {}
StringRef(const std::string & s) : data(s.data()), size(s.size()) {}
StringRef() = default;
std::string toString() const { return std::string(data, size); }
explicit operator std::string() const { return toString(); }
};
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using StringRefs = std::vector<StringRef>;
#if defined(__x86_64__)
/** Сравнение строк на равенство.
* Подход является спорным и выигрывает не во всех случаях.
* Подробнее смотрите hash_map_string_2.cpp
*/
inline bool compareSSE2(const char * p1, const char * p2)
{
return 0xFFFF == _mm_movemask_epi8(_mm_cmpeq_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p1)),
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p2))));
}
inline bool compareSSE2x4(const char * p1, const char * p2)
{
return 0xFFFF == _mm_movemask_epi8(
_mm_and_si128(
_mm_and_si128(
_mm_cmpeq_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p1)),
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p2))),
_mm_cmpeq_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p1) + 1),
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p2) + 1))),
_mm_and_si128(
_mm_cmpeq_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p1) + 2),
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p2) + 2)),
_mm_cmpeq_epi8(
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p1) + 3),
_mm_loadu_si128(reinterpret_cast<const __m128i *>(p2) + 3)))));
}
inline bool memequalSSE2Wide(const char * p1, const char * p2, size_t size)
{
while (size >= 64)
{
if (compareSSE2x4(p1, p2))
{
p1 += 64;
p2 += 64;
size -= 64;
}
else
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return false;
}
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switch ((size % 64) / 16)
{
case 3: if (!compareSSE2(p1 + 32, p2 + 32)) return false;
case 2: if (!compareSSE2(p1 + 16, p2 + 16)) return false;
case 1: if (!compareSSE2(p1 , p2 )) return false;
case 0: break;
}
p1 += (size % 64) / 16 * 16;
p2 += (size % 64) / 16 * 16;
switch (size % 16)
{
case 15: if (p1[14] != p2[14]) return false;
case 14: if (p1[13] != p2[13]) return false;
case 13: if (p1[12] != p2[12]) return false;
case 12: if (reinterpret_cast<const uint32_t *>(p1)[2] == reinterpret_cast<const uint32_t *>(p2)[2]) goto l8; else return false;
case 11: if (p1[10] != p2[10]) return false;
case 10: if (p1[9] != p2[9]) return false;
case 9: if (p1[8] != p2[8]) return false;
l8: case 8: return reinterpret_cast<const uint64_t *>(p1)[0] == reinterpret_cast<const uint64_t *>(p2)[0];
case 7: if (p1[6] != p2[6]) return false;
case 6: if (p1[5] != p2[5]) return false;
case 5: if (p1[4] != p2[4]) return false;
case 4: return reinterpret_cast<const uint32_t *>(p1)[0] == reinterpret_cast<const uint32_t *>(p2)[0];
case 3: if (p1[2] != p2[2]) return false;
case 2: return reinterpret_cast<const uint16_t *>(p1)[0] == reinterpret_cast<const uint16_t *>(p2)[0];
case 1: if (p1[0] != p2[0]) return false;
case 0: break;
}
return true;
}
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#endif
inline bool operator== (StringRef lhs, StringRef rhs)
{
if (lhs.size != rhs.size)
return false;
if (lhs.size == 0)
return true;
#if defined(__x86_64__)
return memequalSSE2Wide(lhs.data, rhs.data, lhs.size);
#else
return 0 == memcmp(lhs.data, rhs.data, lhs.size);
#endif
}
inline bool operator!= (StringRef lhs, StringRef rhs)
{
return !(lhs == rhs);
}
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inline bool operator< (StringRef lhs, StringRef rhs)
{
int cmp = memcmp(lhs.data, rhs.data, std::min(lhs.size, rhs.size));
return cmp < 0 || (cmp == 0 && lhs.size < rhs.size);
}
inline bool operator> (StringRef lhs, StringRef rhs)
{
int cmp = memcmp(lhs.data, rhs.data, std::min(lhs.size, rhs.size));
return cmp > 0 || (cmp == 0 && lhs.size > rhs.size);
}
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/** Хэш-функции.
* Можно использовать либо CityHash64,
* либо функцию на основе инструкции crc32,
* которая является заведомо менее качественной, но на реальных наборах данных,
* при использовании в хэш-таблице, работает существенно быстрее.
* Подробнее см. hash_map_string_3.cpp
*/
#if defined(__x86_64__)
#ifdef __SSE4_1__
#include <smmintrin.h>
#else
inline uint64 _mm_crc32_u64(uint64 crc, uint64 value)
{
asm("crc32q %[value], %[crc]\n" : [crc] "+r" (crc) : [value] "rm" (value));
return crc;
}
#endif
/// Кусочки взяты из CityHash.
inline uint64 hashLen16(uint64 u, uint64 v)
{
return Hash128to64(uint128(u, v));
}
inline uint64 shiftMix(uint64 val)
{
return val ^ (val >> 47);
}
inline uint64 rotateByAtLeast1(uint64 val, int shift)
{
return (val >> shift) | (val << (64 - shift));
}
inline size_t hashLessThan8(const char * data, size_t size)
{
static constexpr uint64 k2 = 0x9ae16a3b2f90404fULL;
static constexpr uint64 k3 = 0xc949d7c7509e6557ULL;
if (size >= 4)
{
uint64 a = *reinterpret_cast<const uint32_t *>(data);;
return hashLen16(size + (a << 3), *reinterpret_cast<const uint32_t *>(data + size - 4));
}
if (size > 0)
{
uint8 a = data[0];
uint8 b = data[size >> 1];
uint8 c = data[size - 1];
uint32 y = static_cast<uint32>(a) + (static_cast<uint32>(b) << 8);
uint32 z = size + (static_cast<uint32>(c) << 2);
return shiftMix(y * k2 ^ z * k3) * k2;
}
return k2;
}
inline size_t hashLessThan16(const char * data, size_t size)
{
if (size > 8)
{
uint64 a = *reinterpret_cast<const uint64_t *>(data);
uint64 b = *reinterpret_cast<const uint64_t *>(data + size - 8);
return hashLen16(a, rotateByAtLeast1(b + size, size)) ^ b;
}
return hashLessThan8(data, size);
}
struct CRC32Hash
{
size_t operator() (StringRef x) const
{
const char * pos = x.data;
size_t size = x.size;
if (size == 0)
return 0;
if (size < 8)
{
return hashLessThan8(x.data, x.size);
}
const char * end = pos + size;
size_t res = -1ULL;
do
{
uint64_t word = *reinterpret_cast<const uint64_t *>(pos);
res = _mm_crc32_u64(res, word);
pos += 8;
} while (pos + 8 < end);
uint64_t word = *reinterpret_cast<const uint64_t *>(end - 8); /// Не уверен, что это нормально.
res = _mm_crc32_u64(res, word);
return res;
}
};
struct StringRefHash : CRC32Hash {};
#else
struct StringRefHash
{
size_t operator() (StringRef x) const
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{
return CityHash64(x.data, x.size);
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}
};
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#endif
namespace std
{
template <>
struct hash<StringRef> : public StringRefHash {};
}
namespace ZeroTraits
{
inline bool check(StringRef x) { return 0 == x.size; }
inline void set(StringRef & x) { x.size = 0; }
};
inline bool operator==(StringRef lhs, const char * rhs)
{
for (size_t pos = 0; pos < lhs.size; ++pos)
if (!rhs[pos] || lhs.data[pos] != rhs[pos])
return false;
return true;
}
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inline std::ostream & operator<<(std::ostream & os, const StringRef & str)
{
if (str.data)
os.write(str.data, str.size);
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return os;
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}