When working at lower-levels, sometimes it pays to conserve bits. Binary formats sometimes use all of the bits they are given - when I was working with MIDI, I came across this a lot. (If you have a full int, you might as well use all 32 of those guys.)
On a more practical note, 16bit color is often 5bits red, 6bits green, and 5bits blue. A color is stored as a 16 bit integer in the format rrrrrggggggbbbbb,
where each letter represents a bit.
It isn't difficult to write code to extract these bit fields, but to make it faster and more readable, I wrote some Python to write the C for me.
The Python script takes a string like "00rrr000" and outputs C code with the appropriate shifts and masks.
Bit tools. Example usage:
10 bits are required to store values up to 640
2 ** 10 = 1024
> print tobinary(46)
> print frombinary('1100_1100')
> pattern('00rrr000', True)
r is a 3bit number
unsigned char packed |= r<<3;
unsigned char r = (packed & 0x3f)>>3; //packed & 0b00111111
b is a 3bit number
unsigned char packed |= b;
unsigned char b = packed & 0x7; //packed & 0b00000111
I find "00rrr000" to be a lot clearer than '(packed & 0x3f)>>3' .