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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namespace DB
{
/// Штука, чтобы не создавать строки для поиска подстроки в хэш таблице.
struct StringRef
{
const char * data;
size_t size;
StringRef(const char * data_, size_t size_) : data(data_), size(size_) {}
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StringRef(const unsigned char * data_, size_t size_) : data(reinterpret_cast<const char *>(data_)), size(size_) {}
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StringRef(const std::string & s) : data(s.data()), size(s.size()) {}
StringRef() : data(NULL), size(0) {}
std::string toString() const { return std::string(data, size); }
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};
typedef std::vector<StringRef> StringRefs;
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inline bool operator==(StringRef lhs, StringRef rhs)
{
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/// Так почему-то быстрее, чем return lhs.size == rhs.size && 0 == memcmp(lhs.data, rhs.data, lhs.size);
if (lhs.size != rhs.size)
return false;
for (size_t pos = 0; pos < lhs.size; ++pos)
if (lhs.data[pos] != rhs.data[pos])
return false;
return true;
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}
inline bool operator!=(StringRef lhs, StringRef rhs)
{
return !(lhs == rhs);
}
struct StringRefHash
{
inline size_t operator() (StringRef x) const
{
return CityHash64(x.data, x.size);
}
};
struct StringRefZeroTraits
{
static inline bool check(DB::StringRef x) { return NULL == x.data; }
static inline void set(DB::StringRef & x) { x.data = NULL; }
};
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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}
namespace std
{
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template <>
struct hash<DB::StringRef>
{
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size_t operator()(const DB::StringRef & x) const
{
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return CityHash64(x.data, x.size);
}
};
}