C/C++ Code to treat a character array as a bitstream

Question

I have a big lump of binary data in a char[] array which I need to interpret as an array of packed 6-bit values.

I could sit down and write some code to do

Answer 1

This may not work for sizes greater than 8, depending on endian system. It's basically what Marco posted, though I'm not entirely sure why he'd gather one bit at a time.

int get_bits(char* data, unsigned int bitOffset, unsigned int numBits) {
    numBits = pow(2,numBits) - 1; //this will only work up to 32 bits, of course
    data += bitOffset/8;
    bitOffset %= 8;
    return (*((int*)data) >> bitOffset) & numBits;  //little endian
    //return (flip(data[0]) >> bitOffset) & numBits; //big endian
}

//flips from big to little or vice versa
int flip(int x) {
    char temp, *t = (char*)&x;
    temp = t[0];
    t[0] = t[3];
    t[3] = temp;
    temp = t[1];
    t[1] = t[2];
    t[2] = temp;
    return x;
}