#pragma once

#include <Columns/IColumn.h>


/// Common helper methods for implementation of different columns.

namespace DB
{

/// Counts how many bytes of `filt` are greater than zero.
size_t countBytesInFilter(const IColumn::Filter & filt);

/// Returns vector with num_columns elements. vector[i] is the count of i values in selector.
/// Selector must contain values from 0 to num_columns - 1. NOTE: this is not checked.
std::vector<size_t> countColumnsSizeInSelector(IColumn::ColumnIndex num_columns, const IColumn::Selector & selector);

/// Returns true, if the memory contains only zeros.
bool memoryIsZero(const void * data, size_t size);


/// The general implementation of `filter` function for ColumnArray and ColumnString.
template <typename T>
void filterArraysImpl(
    const PaddedPODArray<T> & src_elems, const IColumn::Offsets & src_offsets,
    PaddedPODArray<T> & res_elems, IColumn::Offsets & res_offsets,
    const IColumn::Filter & filt, ssize_t result_size_hint);

/// Same as above, but not fills res_offsets.
template <typename T>
void filterArraysImplOnlyData(
    const PaddedPODArray<T> & src_elems, const IColumn::Offsets & src_offsets,
    PaddedPODArray<T> & res_elems,
    const IColumn::Filter & filt, ssize_t result_size_hint);

}