Get ints (of various sizes) from boolean array

Question

OK, say I have a boolean array called bits, and an int called cursor

I know I can access individual bits by using bits[cursor], and that I can use bit logic to get larger datatypes from bits, for example:

short result = (bits[cursor] << 3) |
    (bits[cursor+1] << 2) | 
    (bits[cursor+2] << 1) |
     bits[cursor+3];

This is going to result in lines and lines of code when reading larger types like int32 and int64 though.

Is it possible to do a cast of some kind and achieve the same result? I'm not concerned about safety at all in this context (these functions will be wrapped into a class that handles that)

Say I wanted to get an uint64_t out of bits, starting at an arbitrary address specified by cursor, when cursor isn't necessarily a multiple of 64; is this possible by a cast? I thought this

uint64_t result = (uint64_t *)(bits + cursor)[0];

Would work, but it doesn't want to compile.

Sorry I know this is a dumb question, I'm quite inexperienced with pointer math. I'm not looking just for a short solution, I'm also looking for a breakdown of the syntax if anyone would be kind enough.

Thanks!

Answer 1

You could try something like this and cast the result to your target data size.

uint64_t bitsToUint64(bool *bits, unsigned int bitCount)
{
    uint64_t result = 0;
    uint64_t tempBits = 0;
    if(bitCount > 0 && bitCount <= 64)
    {
        for(unsigned int i = 0, j = bitCount - 1; i < bitCount; i++, j--)
        {
            tempBits = (bits[i])?1:0;
            result |= (tempBits << j);
        }
    }
    return result;
}