(* hex to raw bytes *)
let rec hex_to_raw hexstring = 
  let rec hexraw hexstr rawstr = 
    let tophex = String.sub hexstr 0 2 in
    let topint = int_of_string ("0x" ^ tophex) in
    let newrawstr = rawstr ^ (Char.chr topint) in
    let remlen = (String.length hexstr) - 2  in
    let newhexraw = String.sub 2 remlen in
    if remlen == 0 then newrawstr 
    else hexraw newhexraw newrawstr
  hexraw hexstring "" ;;
 
hex_to_raw "badf00d"
 
 
let b64_to_raw b64string =
  rawstring ;;
 
let raw_to_hex rawstring =
  rawstring ;;
 
let raw_to_b64 rawstring =
  rawstring ;;
 
Printf.printf "%s" (raw_to_b64 (hex_to_raw "badf00d"))
 
 
 

KCogaGV4IHRvIHJhdyBieXRlcyAqKQpsZXQgcmVjIGhleF90b19yYXcgaGV4c3RyaW5nID0gCiAgbGV0IHJlYyBoZXhyYXcgaGV4c3RyIHJhd3N0ciA9IAogICAgbGV0IHRvcGhleCA9IFN0cmluZy5zdWIgaGV4c3RyIDAgMiBpbgogICAgbGV0IHRvcGludCA9IGludF9vZl9zdHJpbmcgKCIweCIgXiB0b3BoZXgpIGluCiAgICBsZXQgbmV3cmF3c3RyID0gcmF3c3RyIF4gKENoYXIuY2hyIHRvcGludCkgaW4KICAgIGxldCByZW1sZW4gPSAoU3RyaW5nLmxlbmd0aCBoZXhzdHIpIC0gMiAgaW4KICAgIGxldCBuZXdoZXhyYXcgPSBTdHJpbmcuc3ViIDIgcmVtbGVuIGluCiAgICBpZiByZW1sZW4gPT0gMCB0aGVuIG5ld3Jhd3N0ciAKICAgIGVsc2UgaGV4cmF3IG5ld2hleHJhdyBuZXdyYXdzdHIKICBoZXhyYXcgaGV4c3RyaW5nICIiIDs7CgpoZXhfdG9fcmF3ICJiYWRmMDBkIgoKCmxldCBiNjRfdG9fcmF3IGI2NHN0cmluZyA9CiAgcmF3c3RyaW5nIDs7CgpsZXQgcmF3X3RvX2hleCByYXdzdHJpbmcgPQogIHJhd3N0cmluZyA7OwoKbGV0IHJhd190b19iNjQgcmF3c3RyaW5nID0KICByYXdzdHJpbmcgOzsKClByaW50Zi5wcmludGYgIiVzIiAocmF3X3RvX2I2NCAoaGV4X3RvX3JhdyAiYmFkZjAwZCIpKQoKCg==