Selecting and Assigning to a Range of Bits

#include "hls/ap_int.hpp"
#include <iostream>
#include <stdio.h>

using namespace hls;

    //...
    ap_uint<8> Aa(0xBC);
    std::cout << "Aa = " << Aa << std::endl;
    ap_int<4> Bb = Aa(7, 4); // Bb initialized as 0xB; "Aa(7, 4)" is equivalent
                             // to "Aa.range(7, 4)"
    std::cout << "Bb = " << Bb << std::endl;
    ap_int<4> Cc = Aa[2]; // Cc initialized as 0x1
                          // Aa[2] is zero extended to match widths
    std::cout << "Cc = " << Cc << std::endl;

    Aa(3, 0) =
        0xA; // Aa becomes 0xBA; "Aa(3, 0) is equivalent to "Aa.range(3, 0)"
    std::cout << "Aa = " << Aa << std::endl;

    Aa.byte(1, 4) = 0xC; // Aa becomes 0xCA;
    std::cout << "Aa = " << Aa << std::endl;

    Aa.bytes(3, 2, 2) = 0xD; // AA becomes 0xDA
    std::cout << "Aa = " << Aa << std::endl;

On C++ arbitrary precision types num(a, b) (or num.range(a, b)) will select and create a reference to the underlying arbitrary precision value. The operator num[a] selects and creates a reference to a single bit. This reference can be assigned to, and used to access the underlying data. The arbitrary precision num.byte(n, s = 8) function selects and creates a reference to the n-th byte of the number which can be assigned to and used to access the underlying data. Similarly, the num.bytes(m, n, s = 8) function selects and creates a reference to a range of bytes from the m-th to the n-th byte (inclusive) of the number. In both functions, the last argument is an optional argument which defines the number of bits per byte, and defaults to 8.