Question

Hi I need to convert a hex number to binary number in C++. It represents a 4 by 8 binary image. For example, the following hex number 0xc00e90 represent the image:

00000000
11000000
00001110
10010000

Here’s my working solution. u is the input hex #, and image is the bool array [4][8]. But I’m pretty sure this is not the optimal solution, what would be the better way to implement this?

    for(int i=0;i<4;i++)
{
    std::bitset<8> bit((u>>(3-i)*8)&0xFF);
    cout<<bit<<"\n";
    for (int j=0;j<8;j++)
    {
        image[i][j]=(bool) bit[7-j];    
    }
}

Answer 1

Actually u is not a hex number, it is just a number without a base until you represent them with some digits of some base. Your solution is fine, another way of doing with without creating a bitset:

uint32_t uu = u;
uint32_t mask = 0x80000000;
for (uint8_t i = 0; i < 32; i++) {
  image[i / 8][i % 8] = (bool) (uu & mask == mask);
  mask >>= 1;
}