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#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypesNumber.h>
#include <Formats/FormatSettings.h>
#include <Columns/ColumnsNumber.h>
#include <IO/WriteBufferFromString.h>
#include <Common/UTF8Helpers.h>
#include <Common/assert_cast.h>
namespace DB
{
/** visibleWidth(x) - calculates the approximate width when outputting the value in a text form to the console.
* In fact it calculate the number of Unicode code points.
* It does not support zero width and full width characters, combining characters, etc.
*/
class FunctionVisibleWidth : public IFunction
{
public:
static constexpr auto name = "visibleWidth";
static FunctionPtr create(ContextPtr)
{
return std::make_shared<FunctionVisibleWidth>();
}
bool useDefaultImplementationForNulls() const override { return false; }
ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
/// Get the name of the function.
String getName() const override
{
return name;
}
size_t getNumberOfArguments() const override
{
return 1;
}
DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
{
return std::make_shared<DataTypeUInt64>();
}
bool useDefaultImplementationForConstants() const override { return true; }
/// Execute the function on the columns.
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
{
const auto & src = arguments[0];
size_t size = input_rows_count;
auto res_col = ColumnUInt64::create(size);
auto & res_data = assert_cast<ColumnUInt64 &>(*res_col).getData();
/// For simplicity reasons, function is implemented by serializing into temporary buffer.
String tmp;
FormatSettings format_settings;
auto serialization = src.type->getDefaultSerialization();
for (size_t i = 0; i < size; ++i)
{
{
WriteBufferFromString out(tmp);
serialization->serializeText(*src.column, i, out, format_settings);
}
res_data[i] = UTF8::countCodePoints(reinterpret_cast<const UInt8 *>(tmp.data()), tmp.size());
}
return res_col;
}
};
REGISTER_FUNCTION(VisibleWidth)
{
factory.registerFunction<FunctionVisibleWidth>();
}
}
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