ClickHouse/base/base/StringRef.h
2024-02-27 14:37:21 +01:00

379 lines
11 KiB
C++

#pragma once
#include <cassert>
#include <stdexcept> // for std::logic_error
#include <string>
#include <type_traits>
#include <vector>
#include <functional>
#include <iosfwd>
#include <base/defines.h>
#include <base/types.h>
#include <base/unaligned.h>
#include <base/simd.h>
#include <city.h>
#if defined(__SSE2__)
#include <emmintrin.h>
#endif
#if defined(__SSE4_2__)
#include <smmintrin.h>
#include <nmmintrin.h>
#define CRC_INT _mm_crc32_u64
#endif
#if defined(__aarch64__) && defined(__ARM_FEATURE_CRC32)
#include <arm_acle.h>
#define CRC_INT __crc32cd
#endif
#if defined(__aarch64__) && defined(__ARM_NEON)
#include <arm_neon.h>
#pragma clang diagnostic ignored "-Wreserved-identifier"
#endif
#if defined(__s390x__)
#include <base/crc32c_s390x.h>
#define CRC_INT s390x_crc32c
#endif
/**
* The std::string_view-like container to avoid creating strings to find substrings in the hash table.
*/
struct StringRef
{
const char * data = nullptr;
size_t size = 0;
/// Non-constexpr due to reinterpret_cast.
template <typename CharT>
requires (sizeof(CharT) == 1)
StringRef(const CharT * data_, size_t size_) : data(reinterpret_cast<const char *>(data_)), size(size_)
{
/// Sanity check for overflowed values.
assert(size < 0x8000000000000000ULL);
}
constexpr StringRef(const char * data_, size_t size_) : data(data_), size(size_) {}
StringRef(const std::string & s) : data(s.data()), size(s.size()) {} /// NOLINT
constexpr explicit StringRef(std::string_view s) : data(s.data()), size(s.size()) {}
constexpr StringRef(const char * data_) : StringRef(std::string_view{data_}) {} /// NOLINT
constexpr StringRef() = default;
bool empty() const { return size == 0; }
std::string toString() const { return std::string(data, size); }
explicit operator std::string() const { return toString(); }
std::string_view toView() const { return std::string_view(data, size); }
constexpr explicit operator std::string_view() const { return std::string_view(data, size); }
};
using StringRefs = std::vector<StringRef>;
#if defined(__SSE2__)
/** Compare strings for equality.
* The approach is controversial and does not win in all cases.
* For more information, see hash_map_string_2.cpp
*/
inline bool compare8(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 compare64(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)))));
}
#elif defined(__aarch64__) && defined(__ARM_NEON)
inline bool compare8(const char * p1, const char * p2)
{
uint64_t mask = getNibbleMask(vceqq_u8(
vld1q_u8(reinterpret_cast<const unsigned char *>(p1)), vld1q_u8(reinterpret_cast<const unsigned char *>(p2))));
return 0xFFFFFFFFFFFFFFFF == mask;
}
inline bool compare64(const char * p1, const char * p2)
{
uint64_t mask = getNibbleMask(vandq_u8(
vandq_u8(vceqq_u8(vld1q_u8(reinterpret_cast<const unsigned char *>(p1)), vld1q_u8(reinterpret_cast<const unsigned char *>(p2))),
vceqq_u8(vld1q_u8(reinterpret_cast<const unsigned char *>(p1 + 16)), vld1q_u8(reinterpret_cast<const unsigned char *>(p2 + 16)))),
vandq_u8(vceqq_u8(vld1q_u8(reinterpret_cast<const unsigned char *>(p1 + 32)), vld1q_u8(reinterpret_cast<const unsigned char *>(p2 + 32))),
vceqq_u8(vld1q_u8(reinterpret_cast<const unsigned char *>(p1 + 48)), vld1q_u8(reinterpret_cast<const unsigned char *>(p2 + 48))))));
return 0xFFFFFFFFFFFFFFFF == mask;
}
#endif
#if defined(__SSE2__) || (defined(__aarch64__) && defined(__ARM_NEON))
inline bool memequalWide(const char * p1, const char * p2, size_t size)
{
/** The order of branches and the trick with overlapping comparisons
* are the same as in memcpy implementation.
* See the comments in base/glibc-compatibility/memcpy/memcpy.h
*/
if (size <= 16)
{
if (size >= 8)
{
/// Chunks of 8..16 bytes.
return unalignedLoad<uint64_t>(p1) == unalignedLoad<uint64_t>(p2)
&& unalignedLoad<uint64_t>(p1 + size - 8) == unalignedLoad<uint64_t>(p2 + size - 8);
}
else if (size >= 4)
{
/// Chunks of 4..7 bytes.
return unalignedLoad<uint32_t>(p1) == unalignedLoad<uint32_t>(p2)
&& unalignedLoad<uint32_t>(p1 + size - 4) == unalignedLoad<uint32_t>(p2 + size - 4);
}
else if (size >= 2)
{
/// Chunks of 2..3 bytes.
return unalignedLoad<uint16_t>(p1) == unalignedLoad<uint16_t>(p2)
&& unalignedLoad<uint16_t>(p1 + size - 2) == unalignedLoad<uint16_t>(p2 + size - 2);
}
else if (size >= 1)
{
/// A single byte.
return *p1 == *p2;
}
return true;
}
while (size >= 64)
{
if (compare64(p1, p2))
{
p1 += 64;
p2 += 64;
size -= 64;
}
else
return false;
}
switch (size / 16) // NOLINT(bugprone-switch-missing-default-case)
{
case 3: if (!compare8(p1 + 32, p2 + 32)) return false; [[fallthrough]];
case 2: if (!compare8(p1 + 16, p2 + 16)) return false; [[fallthrough]];
case 1: if (!compare8(p1, p2)) return false; [[fallthrough]];
default: ;
}
return compare8(p1 + size - 16, p2 + size - 16);
}
#endif
inline bool operator== (StringRef lhs, StringRef rhs)
{
if (lhs.size != rhs.size)
return false;
if (lhs.size == 0)
return true;
#if defined(__SSE2__) || (defined(__aarch64__) && defined(__ARM_NEON))
return memequalWide(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);
}
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);
}
/** Hash functions.
* You can use either CityHash64,
* or a function based on the crc32 statement,
* which is obviously less qualitative, but on real data sets,
* when used in a hash table, works much faster.
* For more information, see hash_map_string_3.cpp
*/
struct StringRefHash64
{
size_t operator() (StringRef x) const
{
return CityHash_v1_0_2::CityHash64(x.data, x.size);
}
};
#if defined(CRC_INT)
/// Parts are taken from CityHash.
inline UInt64 hashLen16(UInt64 u, UInt64 v)
{
return CityHash_v1_0_2::Hash128to64(CityHash_v1_0_2::uint128(u, v));
}
inline UInt64 shiftMix(UInt64 val)
{
return val ^ (val >> 47);
}
inline UInt64 rotateByAtLeast1(UInt64 val, UInt8 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 = unalignedLoadLittleEndian<uint32_t>(data);
return hashLen16(size + (a << 3), unalignedLoadLittleEndian<uint32_t>(data + size - 4));
}
if (size > 0)
{
uint8_t a = data[0];
uint8_t b = data[size >> 1];
uint8_t c = data[size - 1];
uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
uint32_t z = static_cast<uint32_t>(size) + (static_cast<uint32_t>(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 = unalignedLoadLittleEndian<UInt64>(data);
UInt64 b = unalignedLoadLittleEndian<UInt64>(data + size - 8);
return hashLen16(a, rotateByAtLeast1(b + size, static_cast<UInt8>(size))) ^ b;
}
return hashLessThan8(data, size);
}
struct CRC32Hash
{
unsigned operator() (StringRef x) const
{
const char * pos = x.data;
size_t size = x.size;
if (size == 0)
return 0;
chassert(pos);
if (size < 8)
{
return static_cast<unsigned>(hashLessThan8(x.data, x.size));
}
const char * end = pos + size;
unsigned res = -1U;
do
{
UInt64 word = unalignedLoadLittleEndian<UInt64>(pos);
res = static_cast<unsigned>(CRC_INT(res, word));
pos += 8;
} while (pos + 8 < end);
UInt64 word = unalignedLoadLittleEndian<UInt64>(end - 8); /// I'm not sure if this is normal.
res = static_cast<unsigned>(CRC_INT(res, word));
return res;
}
};
struct StringRefHash : CRC32Hash {};
#else
struct CRC32Hash
{
unsigned operator() (StringRef /* x */) const
{
throw std::logic_error{"Not implemented CRC32Hash without SSE"};
}
};
struct StringRefHash : StringRefHash64 {};
#endif
namespace std
{
template <>
struct hash<StringRef> : public StringRefHash {};
}
namespace ZeroTraits
{
inline bool check(const StringRef & x) { return 0 == x.size; }
inline void set(StringRef & x) { x.size = 0; }
}
namespace PackedZeroTraits
{
template <typename Second, template <typename, typename> class PackedPairNoInit>
inline bool check(const PackedPairNoInit<StringRef, Second> p)
{ return 0 == p.key.size; }
template <typename Second, template <typename, typename> class PackedPairNoInit>
inline void set(PackedPairNoInit<StringRef, Second> & p)
{ p.key.size = 0; }
}
std::ostream & operator<<(std::ostream & os, const StringRef & str);