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#pragma once
#include <Common/PODArray.h>
namespace DB
{
/// It's a class which represents the result of weak and fast hash function per row in column.
/// It's usually hardware accelerated CRC32-C.
/// Has function result may be combined to calculate hash for tuples.
///
/// The main purpose why this class needed is to support data initialization. Initially, every bit is 1.
class WeakHash32
{
static constexpr UInt32 kDefaultInitialValue = ~UInt32(0);
public:
using Container = PaddedPODArray<UInt32>;
explicit WeakHash32(size_t size, UInt32 initial_value = kDefaultInitialValue) : data(size, initial_value) {}
WeakHash32(const WeakHash32 & other) { data.assign(other.data); }
void reset(size_t size, UInt32 initial_value = kDefaultInitialValue) { data.assign(size, initial_value); }
const Container & getData() const { return data; }
Container & getData() { return data; }
private:
PaddedPODArray<UInt32> data;
};
}
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