text: #pragma once
  
  #include <ap_int.h>
  
  #define NUM_OF_PAIRS (32)
  
  struct APP_Expand_Data {
    unsigned short prefix_sum[NUM_OF_PAIRS + 1];
    char alpha_array[NUM_OF_PAIRS];
    bool eop;
    unsigned char len; // mark valid number of pairs
  };
  