mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-05 15:21:43 +00:00
454 lines
15 KiB
C++
454 lines
15 KiB
C++
#pragma once
|
||
|
||
#include <DB/Common/StringSearcher.h>
|
||
#include <Poco/UTF8Encoding.h>
|
||
#include <Poco/Unicode.h>
|
||
#include <ext/range.hpp>
|
||
#include <x86intrin.h>
|
||
#include <stdint.h>
|
||
#include <string.h>
|
||
|
||
|
||
/** Поиск подстроки в строке по алгоритму Вольницкого:
|
||
* http://volnitsky.com/project/str_search/
|
||
*
|
||
* haystack и needle могут содержать нулевые байты.
|
||
*
|
||
* Алгоритм:
|
||
* - при слишком маленьком или слишком большом размере needle, или слишком маленьком haystack, используем std::search или memchr;
|
||
* - при инициализации, заполняем open-addressing linear probing хэш-таблицу вида:
|
||
* хэш от биграммы из needle -> позиция этой биграммы в needle + 1.
|
||
* (прибавлена единица только чтобы отличить смещение ноль от пустой ячейки)
|
||
* - в хэш-таблице ключи не хранятся, хранятся только значения;
|
||
* - биграммы могут быть вставлены несколько раз, если они встречаются в needle несколько раз;
|
||
* - при поиске, берём из haystack биграмму, которая должна соответствовать последней биграмме needle (сравниваем с конца);
|
||
* - ищем её в хэш-таблице, если нашли - достаём смещение из хэш-таблицы и сравниваем строку побайтово;
|
||
* - если сравнить не получилось - проверяем следующую ячейку хэш-таблицы из цепочки разрешения коллизий;
|
||
* - если не нашли, пропускаем в haystack почти размер needle байт;
|
||
*
|
||
* Используется невыровненный доступ к памяти.
|
||
*/
|
||
|
||
|
||
namespace DB
|
||
{
|
||
|
||
|
||
/// @todo store lowercase needle to speed up in case there are numerous occurrences of bigrams from needle in haystack
|
||
template <typename CRTP>
|
||
class VolnitskyBase
|
||
{
|
||
protected:
|
||
using offset_t = uint8_t; /// Смещение в needle. Для основного алгоритма, длина needle не должна быть больше 255.
|
||
using ngram_t = uint16_t; /// n-грамма (2 байта).
|
||
|
||
const UInt8 * const needle;
|
||
const size_t needle_size;
|
||
const UInt8 * const needle_end = needle + needle_size;
|
||
/// На сколько двигаемся, если n-грамма из haystack не нашлась в хэш-таблице.
|
||
const size_t step = needle_size - sizeof(ngram_t) + 1;
|
||
|
||
/** max needle length is 255, max distinct ngrams for case-sensitive is (255 - 1), case-insensitive is 4 * (255 - 1)
|
||
* storage of 64K ngrams (n = 2, 128 KB) should be large enough for both cases */
|
||
static const size_t hash_size = 64 * 1024; /// Помещается в L2-кэш.
|
||
offset_t hash[hash_size]; /// Хэш-таблица.
|
||
|
||
/// min haystack size to use main algorithm instead of fallback
|
||
static constexpr auto min_haystack_size_for_algorithm = 20000;
|
||
const bool fallback; /// Нужно ли использовать fallback алгоритм.
|
||
|
||
public:
|
||
/** haystack_size_hint - ожидаемый суммарный размер haystack при вызовах search. Можно не указывать.
|
||
* Если указать его достаточно маленьким, то будет использован fallback алгоритм,
|
||
* так как считается, что тратить время на инициализацию хэш-таблицы не имеет смысла.
|
||
*/
|
||
VolnitskyBase(const char * const needle, const size_t needle_size, size_t haystack_size_hint = 0)
|
||
: needle{reinterpret_cast<const UInt8 *>(needle)}, needle_size{needle_size},
|
||
fallback{
|
||
needle_size < 2 * sizeof(ngram_t) or needle_size >= std::numeric_limits<offset_t>::max() or
|
||
(haystack_size_hint and haystack_size_hint < min_haystack_size_for_algorithm)
|
||
}
|
||
{
|
||
if (fallback)
|
||
return;
|
||
|
||
memset(hash, 0, sizeof(hash));
|
||
|
||
/// int is used here because unsigned can't be used with condition like `i >= 0`, unsigned always >= 0
|
||
for (auto i = static_cast<int>(needle_size - sizeof(ngram_t)); i >= 0; --i)
|
||
self().putNGram(this->needle + i, i + 1);
|
||
}
|
||
|
||
|
||
/// Если не найдено - возвращается конец haystack.
|
||
const UInt8 * search(const UInt8 * const haystack, const size_t haystack_size) const
|
||
{
|
||
if (needle_size == 0)
|
||
return haystack;
|
||
|
||
const auto haystack_end = haystack + haystack_size;
|
||
|
||
if (needle_size == 1 || fallback || haystack_size <= needle_size)
|
||
return self().search_fallback(haystack, haystack_end);
|
||
|
||
/// Будем "прикладывать" needle к haystack и сравнивать n-грам из конца needle.
|
||
const auto * pos = haystack + needle_size - sizeof(ngram_t);
|
||
for (; pos <= haystack_end - needle_size; pos += step)
|
||
{
|
||
/// Смотрим все ячейки хэш-таблицы, которые могут соответствовать n-граму из haystack.
|
||
for (size_t cell_num = toNGram(pos) % hash_size; hash[cell_num];
|
||
cell_num = (cell_num + 1) % hash_size)
|
||
{
|
||
/// Когда нашли - сравниваем побайтово, используя смещение из хэш-таблицы.
|
||
const auto res = pos - (hash[cell_num] - 1);
|
||
|
||
if (self().compare(res))
|
||
return res;
|
||
}
|
||
}
|
||
|
||
/// Оставшийся хвостик.
|
||
return self().search_fallback(pos - step + 1, haystack_end);
|
||
}
|
||
|
||
const char * search(const char * haystack, size_t haystack_size) const
|
||
{
|
||
return reinterpret_cast<const char *>(search(reinterpret_cast<const UInt8 *>(haystack), haystack_size));
|
||
}
|
||
|
||
protected:
|
||
CRTP & self() { return static_cast<CRTP &>(*this); }
|
||
const CRTP & self() const { return const_cast<VolnitskyBase *>(this)->self(); }
|
||
|
||
static const ngram_t & toNGram(const UInt8 * const pos)
|
||
{
|
||
return *reinterpret_cast<const ngram_t *>(pos);
|
||
}
|
||
|
||
void putNGramBase(const ngram_t ngram, const int offset)
|
||
{
|
||
/// Кладём смещение для n-грама в соответствующую ему ячейку или ближайшую свободную.
|
||
size_t cell_num = ngram % hash_size;
|
||
|
||
while (hash[cell_num])
|
||
cell_num = (cell_num + 1) % hash_size; /// Поиск следующей свободной ячейки.
|
||
|
||
hash[cell_num] = offset;
|
||
}
|
||
};
|
||
|
||
|
||
template <bool CaseSensitive, bool ASCII> struct VolnitskyImpl;
|
||
|
||
/// Case sensitive comparison
|
||
template <bool ASCII> struct VolnitskyImpl<true, ASCII> : VolnitskyBase<VolnitskyImpl<true, ASCII>>
|
||
{
|
||
VolnitskyImpl(const char * const needle, const size_t needle_size, const size_t haystack_size_hint = 0)
|
||
: VolnitskyBase<VolnitskyImpl<true, ASCII>>{needle, needle_size, haystack_size_hint},
|
||
fallback_searcher{needle, needle_size}
|
||
{
|
||
}
|
||
|
||
void putNGram(const UInt8 * const pos, const int offset)
|
||
{
|
||
this->putNGramBase(this->toNGram(pos), offset);
|
||
}
|
||
|
||
bool compare(const UInt8 * const pos) const
|
||
{
|
||
/// @todo: maybe just use memcmp for this case and rely on internal SSE optimization as in case with memcpy?
|
||
return fallback_searcher.compare(pos);
|
||
}
|
||
|
||
const UInt8 * search_fallback(const UInt8 * const haystack, const UInt8 * const haystack_end) const
|
||
{
|
||
return fallback_searcher.search(haystack, haystack_end);
|
||
}
|
||
|
||
ASCIICaseSensitiveStringSearcher fallback_searcher;
|
||
};
|
||
|
||
/// Case-insensitive ASCII
|
||
template <> struct VolnitskyImpl<false, true> : VolnitskyBase<VolnitskyImpl<false, true>>
|
||
{
|
||
VolnitskyImpl(const char * const needle, const size_t needle_size, const size_t haystack_size_hint = 0)
|
||
: VolnitskyBase{needle, needle_size, haystack_size_hint}, fallback_searcher{needle, needle_size}
|
||
{
|
||
}
|
||
|
||
void putNGram(const UInt8 * const pos, const int offset)
|
||
{
|
||
union {
|
||
ngram_t n;
|
||
UInt8 c[2];
|
||
};
|
||
|
||
n = toNGram(pos);
|
||
const auto c0_alpha = std::isalpha(c[0]);
|
||
const auto c1_alpha = std::isalpha(c[1]);
|
||
|
||
if (c0_alpha && c1_alpha)
|
||
{
|
||
/// 4 combinations: AB, aB, Ab, ab
|
||
c[0] = std::tolower(c[0]);
|
||
c[1] = std::tolower(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::toupper(c[0]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[1] = std::toupper(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::tolower(c[0]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else if (c0_alpha)
|
||
{
|
||
/// 2 combinations: A1, a1
|
||
c[0] = std::tolower(c[0]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::toupper(c[0]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else if (c1_alpha)
|
||
{
|
||
/// 2 combinations: 0B, 0b
|
||
c[1] = std::tolower(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[1] = std::toupper(c[1]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else
|
||
/// 1 combination: 01
|
||
putNGramBase(n, offset);
|
||
}
|
||
|
||
bool compare(const UInt8 * const pos) const
|
||
{
|
||
return fallback_searcher.compare(pos);
|
||
}
|
||
|
||
const UInt8 * search_fallback(const UInt8 * const haystack, const UInt8 * const haystack_end) const
|
||
{
|
||
return fallback_searcher.search(haystack, haystack_end);
|
||
}
|
||
|
||
ASCIICaseInsensitiveStringSearcher fallback_searcher;
|
||
};
|
||
|
||
/// Case-sensitive UTF-8
|
||
template <> struct VolnitskyImpl<false, false> : VolnitskyBase<VolnitskyImpl<false, false>>
|
||
{
|
||
VolnitskyImpl(const char * const needle, const size_t needle_size, const size_t haystack_size_hint = 0)
|
||
: VolnitskyBase{needle, needle_size, haystack_size_hint}, fallback_searcher{needle, needle_size}
|
||
{
|
||
}
|
||
|
||
void putNGram(const UInt8 * const pos, const int offset)
|
||
{
|
||
union
|
||
{
|
||
ngram_t n;
|
||
UInt8 c[2];
|
||
};
|
||
|
||
n = toNGram(pos);
|
||
|
||
if (isascii(c[0]) && isascii(c[1]))
|
||
{
|
||
const auto c0_al = std::isalpha(c[0]);
|
||
const auto c1_al = std::isalpha(c[1]);
|
||
|
||
if (c0_al && c1_al)
|
||
{
|
||
/// 4 combinations: AB, aB, Ab, ab
|
||
c[0] = std::tolower(c[0]);
|
||
c[1] = std::tolower(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::toupper(c[0]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[1] = std::toupper(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::tolower(c[0]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else if (c0_al)
|
||
{
|
||
/// 2 combinations: A1, a1
|
||
c[0] = std::tolower(c[0]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[0] = std::toupper(c[0]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else if (c1_al)
|
||
{
|
||
/// 2 combinations: 0B, 0b
|
||
c[1] = std::tolower(c[1]);
|
||
putNGramBase(n, offset);
|
||
|
||
c[1] = std::toupper(c[1]);
|
||
putNGramBase(n, offset);
|
||
}
|
||
else
|
||
/// 1 combination: 01
|
||
putNGramBase(n, offset);
|
||
}
|
||
else
|
||
{
|
||
using Seq = UInt8[6];
|
||
|
||
static const Poco::UTF8Encoding utf8;
|
||
|
||
if (UTF8::isContinuationOctet(c[1]))
|
||
{
|
||
/// ngram is inside a sequence
|
||
auto seq_pos = pos;
|
||
UTF8::syncBackward(seq_pos);
|
||
|
||
const auto u32 = utf8.convert(seq_pos);
|
||
const auto l_u32 = Poco::Unicode::toLower(u32);
|
||
const auto u_u32 = Poco::Unicode::toUpper(u32);
|
||
|
||
/// symbol is case-independent
|
||
if (l_u32 == u_u32)
|
||
putNGramBase(n, offset);
|
||
else
|
||
{
|
||
/// where is the given ngram in respect to UTF-8 sequence start?
|
||
const auto seq_ngram_offset = pos - seq_pos;
|
||
|
||
Seq seq;
|
||
|
||
/// put ngram from lowercase
|
||
utf8.convert(l_u32, seq, sizeof(seq));
|
||
c[0] = seq[seq_ngram_offset];
|
||
c[1] = seq[seq_ngram_offset + 1];
|
||
putNGramBase(n, offset);
|
||
|
||
/// put ngram for uppercase
|
||
utf8.convert(u_u32, seq, sizeof(seq));
|
||
c[0] = seq[seq_ngram_offset];
|
||
c[1] = seq[seq_ngram_offset + 1];
|
||
putNGramBase(n, offset);
|
||
}
|
||
}
|
||
else
|
||
{
|
||
/// ngram is on the boundary of two sequences
|
||
/// first sequence may start before u_pos if it is not ASCII
|
||
auto first_seq_pos = pos;
|
||
UTF8::syncBackward(first_seq_pos);
|
||
|
||
const auto first_u32 = utf8.convert(first_seq_pos);
|
||
const auto first_l_u32 = Poco::Unicode::toLower(first_u32);
|
||
const auto first_u_u32 = Poco::Unicode::toUpper(first_u32);
|
||
|
||
/// second sequence always start immediately after u_pos
|
||
auto second_seq_pos = pos + 1;
|
||
|
||
const auto second_u32 = utf8.convert(second_seq_pos);
|
||
const auto second_l_u32 = Poco::Unicode::toLower(second_u32);
|
||
const auto second_u_u32 = Poco::Unicode::toUpper(second_u32);
|
||
|
||
/// both symbols are case-independent
|
||
if (first_l_u32 == first_u_u32 && second_l_u32 == second_u_u32)
|
||
putNGramBase(n, offset);
|
||
else if (first_l_u32 == first_u_u32)
|
||
{
|
||
/// first symbol is case-independent
|
||
Seq seq;
|
||
|
||
/// put ngram for lowercase
|
||
utf8.convert(second_l_u32, seq, sizeof(seq));
|
||
c[1] = seq[0];
|
||
putNGramBase(n, offset);
|
||
|
||
/// put ngram from uppercase
|
||
utf8.convert(second_u_u32, seq, sizeof(seq));
|
||
c[1] = seq[0];
|
||
putNGramBase(n, offset);
|
||
}
|
||
else if (second_l_u32 == second_u_u32)
|
||
{
|
||
/// second symbol is case-independent
|
||
|
||
/// where is the given ngram in respect to the first UTF-8 sequence start?
|
||
const auto seq_ngram_offset = pos - first_seq_pos;
|
||
|
||
Seq seq;
|
||
|
||
/// put ngram for lowercase
|
||
utf8.convert(second_l_u32, seq, sizeof(seq));
|
||
c[0] = seq[seq_ngram_offset];
|
||
putNGramBase(n, offset);
|
||
|
||
/// put ngram for uppercase
|
||
utf8.convert(second_u_u32, seq, sizeof(seq));
|
||
c[0] = seq[seq_ngram_offset];
|
||
putNGramBase(n, offset);
|
||
}
|
||
else
|
||
{
|
||
/// where is the given ngram in respect to the first UTF-8 sequence start?
|
||
const auto seq_ngram_offset = pos - first_seq_pos;
|
||
|
||
Seq first_l_seq, first_u_seq, second_l_seq, second_u_seq;
|
||
|
||
utf8.convert(first_l_u32, first_l_seq, sizeof(first_l_seq));
|
||
utf8.convert(first_u_u32, first_u_seq, sizeof(first_u_seq));
|
||
utf8.convert(second_l_u32, second_l_seq, sizeof(second_l_seq));
|
||
utf8.convert(second_u_u32, second_u_seq, sizeof(second_u_seq));
|
||
|
||
/// ngram for ll
|
||
c[0] = first_l_seq[seq_ngram_offset];
|
||
c[1] = second_l_seq[0];
|
||
putNGramBase(n, offset);
|
||
|
||
/// ngram for lU
|
||
c[0] = first_l_seq[seq_ngram_offset];
|
||
c[1] = second_u_seq[0];
|
||
putNGramBase(n, offset);
|
||
|
||
/// ngram for Ul
|
||
c[0] = first_u_seq[seq_ngram_offset];
|
||
c[1] = second_l_seq[0];
|
||
putNGramBase(n, offset);
|
||
|
||
/// ngram for UU
|
||
c[0] = first_u_seq[seq_ngram_offset];
|
||
c[1] = second_u_seq[0];
|
||
putNGramBase(n, offset);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
bool compare(const UInt8 * const pos) const
|
||
{
|
||
return fallback_searcher.compare(pos);
|
||
}
|
||
|
||
const UInt8 * search_fallback(const UInt8 * const haystack, const UInt8 * const haystack_end) const
|
||
{
|
||
return fallback_searcher.search(haystack, haystack_end);
|
||
}
|
||
|
||
UTF8CaseInsensitiveStringSearcher fallback_searcher;
|
||
};
|
||
|
||
|
||
using Volnitsky = VolnitskyImpl<true, true>;
|
||
using VolnitskyUTF8 = VolnitskyImpl<true, false>; /// exactly same as Volnitsky
|
||
using VolnitskyCaseInsensitive = VolnitskyImpl<false, true>; /// ignores non-ASCII bytes
|
||
using VolnitskyCaseInsensitiveUTF8 = VolnitskyImpl<false, false>;
|
||
|
||
|
||
}
|