vim RNG (/dev/urandom)

devurandom.vim

" I like picking a random colorscheme, but I hate the way it's done in most vim scripts
" -- localtime(), system("echo $RANDOM"), etc etc.
" And I wanted to try this gist thing...
function! DevUrandom()
    let rv = 0
    " readline reads 4096 bytes at a time(think fread())
    " and returns a *list* of lines.
    " Don't only read one line because:
    " - we read more anyway, and
    " - a short line means 0 has 1/256 probability rather than 1/4G!
    for line in readfile('/dev/urandom', 'b', 4)
        let i = 0
        " use any hash function you wish
        while(i < len(line))
            let rv = or(rv * 256, (rv / 256) % 256) " rotate 8 bits
            let rv = xor(rv, char2nr(line[i])) " xor lower bits
            let i = i + 1
        endwhile
    endfor
    " int32 overflow!
    if(rv < 0)
        let rv = 0 - (rv + 1) " think INT32_MIN
    endif
    return rv
endfunction