Alternative to digitalReadFast for Arduino 101?

I'm having trouble reading too fast encoders with interrupts and normal digitalRead.

Is there any alternative to the library digitalReadFast for arduino 101?

There are multiple libs for reading encoders.
You could start by adding a link to the exact encoder you are using.

Rotary encoders especially cheaper ones suffer from bounce and its not uncommon for them to skip counts or mis-read.

A schematic may also be helpful too.