**Use case**

Convert bitmask to position.
It would allow us to directly use FLAT dictionary or Enum datatype without jumping around slow `bitmasktoArray` and `arrayMap`

**Describe the solution you'd like**

```
SELECT
    arrayMap(x -> log2(x), bitmaskToArray(100)) AS bitmask,
    bitPositions(100)  AS bitpositions

┌─bitmask─┬─bitpositions─┐
│ [2,5,6] │ [2,5,6]      │
└─────────┴──────────────┘
```

{
        return name;
    }
    size_t getNumberOfArguments() const override { return 1; }
    bool isInjective(const ColumnsWithTypeAndName &) const override { return true; }
    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        if (!WhichDataType(arguments[0]).isUInt64())
            throw Exception("Illegal type " + arguments[0]->getName() + " of argument of function " + getName() + ", expected UInt64",
            ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        return std::make_shared<DataTypeString>();
    }
    static void formatMAC(UInt64 mac, UInt8 * out)
    {
        
        
        writeHexByteUppercase(mac >> 40, &out[0]);
        out[2] = ':';
        writeHexByteUppercase(mac >> 32, &out[3]);
        out[5] = ':';
        writeHexByteUppercase(mac >> 24, &out[6]);
        out[8] = ':';
        writeHexByteUppercase(mac >> 16, &out[9]);
        out[11] = ':';
        writeHexByteUppercase(mac >> 8, &out[12]);
        out[14] = ':';
        writeHexByteUppercase(mac, &out[15]);
        out[17] = '\0';
    }
    bool useDefaultImplementationForConstants() const override { return true; }