*[<Null safety>](https://dart.dev/null-safety)*
PseudoFile.readWriteStr(int _capacity, ReadFnStr rfn, WriteFnStr wfn)
PseudoFile.readWriteStr(this._capacity, ReadFnStr rfn, WriteFnStr wfn) : assert(_capacity > 0), assert(rfn != null), assert(wfn != null) { _readFn = _getReadFn(rfn); _writeFn = _getWriteFn(wfn); }