jump to byte offset in vim

" jump to byte offset
" (http://vi.stackexchange.com/questions/3845/go-to-x-bytes-from-here)
let s:last_jump_bytes = 0
function! JumpToByte(byte_nr, mul)
    let crt_byte = line2byte(line('.')) + col('.') - 1
    if (a:byte_nr == 0)
        let dst_byte = crt_byte + a:mul * s:last_jump_bytes
    else
        let dst_byte = crt_byte + a:mul * a:byte_nr
        let s:last_jump_bytes = a:byte_nr
    endif
    let dst_byte = dst_byte > 1? dst_byte : 1
    execute "go " . dst_byte
endfunction

nnoremap <expr> <silent> GO  ":<c-u>call JumpToByte(" . v:count . ",+1)<cr>"
nnoremap <expr> <silent> Go  ":<c-u>call JumpToByte(" . v:count . ",-1)<cr>"
" for symmetry with 'gg', and .. G is now a prefix ^^^
nnoremap GG G