Bit, Bytes and Pixels
Intro I've been thinking about writing this post for a while and some recent work optimizing an e-ink library reminded me to get started. A common theme I see in a lot of the (other people's) code that I optimize is that simple bit/byte/pixel operations are turned into overly complicated code with lots of compares and branches. The authors tend to tie themselves in knots to write working code, but the common theme is that they don't really understand how computers do their work. They approach the topic of bit manipulation as if each bit has a life of its own and is not somehow related to the other bits in the variable. Computers these days are super complicated machines, but fundamental parts of the design haven't changed from the earliest 4-bit digital computer to today's multi-core supercomputers. The part I'm talking about is the concept that all digital data is defined as different sized groups of bits; a bit is just an on (high) or off (low) signal on a s