[Nix-dev] Convert sha1 from base64 into "normal" string

[Игорь Пашев]

Updated to fix padding
https://gist.github.com/ip1981/35b660779ad6935338ca5d09bc2f9fca

strBase64:

let

  inherit (builtins)
    concatStringsSep genList stringLength substring trace ;

  base64 = {
    # n=0; for l in {A..Z} {a..z} {0..9} + /; do printf '"%s" = %2s; '
$l $n; (( n++ )); (( n % 8 )) || echo; done
    "A" =  0; "B" =  1; "C" =  2; "D" =  3; "E" =  4; "F" =  5; "G" =
6; "H" =  7;
    "I" =  8; "J" =  9; "K" = 10; "L" = 11; "M" = 12; "N" = 13; "O" =
14; "P" = 15;
    "Q" = 16; "R" = 17; "S" = 18; "T" = 19; "U" = 20; "V" = 21; "W" =
22; "X" = 23;
    "Y" = 24; "Z" = 25; "a" = 26; "b" = 27; "c" = 28; "d" = 29; "e" =
30; "f" = 31;
    "g" = 32; "h" = 33; "i" = 34; "j" = 35; "k" = 36; "l" = 37; "m" =
38; "n" = 39;
    "o" = 40; "p" = 41; "q" = 42; "r" = 43; "s" = 44; "t" = 45; "u" =
46; "v" = 47;
    "w" = 48; "x" = 49; "y" = 50; "z" = 51; "0" = 52; "1" = 53; "2" =
54; "3" = 55;
    "4" = 56; "5" = 57; "6" = 58; "7" = 59; "8" = 60; "9" = 61; "+" =
62; "/" = 63;
  };

  quartet_to_int24 = q:
    # https://en.wikipedia.org/wiki/Base64
    let
      s = n: assert (stringLength q == 4); substring (3 - n) 1 q;
      d = n: base64.${s n};
    in if s 0 != "=" then
        64 * (64 * (64 * (d 3) + (d 2)) + (d 1)) + (d 0)
      else if s 1 != "=" then
        64 * (64 * (64 * (d 3) + (d 2)) + (d 1)) / 256 # right shift by 8 bits
      else
        64 * (64 * (64 * (d 3) + (d 2))) / 65536 # right shift by 16 bits
      ;

  int24_to_hex = i: # 16777215 (0xFFFFFF, 2^24-1) max
    let
      hex = "0123456789abcdef";
      toHex = n:
        let
          d = n / 16;
          r = n - 16 * d;
        in "${if d != 0 then toHex d else ""}${substring r 1 hex}";
    in assert (0 <= i && i <= 16777215); toHex i;

  quartets = s:
    let
      l = stringLength s;
      h = substring 0 4 s;
      t = substring 4 (l - 4) s;
    in [h] ++ (if t != "" then quartets t else []);


  quartet_to_hex = q: # base64 quartet into hex with padding
    let
      i = quartet_to_int24 q;
      h = int24_to_hex i;
      s = if substring 2 1 q == "=" then 1
          else if substring 3 1 q == "=" then 2
          else 3; # number of bytes
      w = s * 2; # number of hexadecimal digits
      filler = concatStringsSep "" (genList (_: "0") (w - stringLength h));
    in "${filler}${h}";

/*

  FIXME: usage of library functions like concatMapString
  causes very cryptic errors:

  # nix-instantiate --eval --expr 'import ./fromBase64.nix
"kjOzmCPxyw0bPciMsGSh5q+bT9g="' --show-trace
  error: while evaluating anonymous function at
.../fromBase64.nix:1:1, called from (string):1:18:
  value is a function while a set was expected, at .../fromBase64.nix:3:4

*/

in concatStringsSep "" (map quartet_to_hex (quartets strBase64))


2016-10-11 14:53 GMT+03:00 Игорь Пашев <pashev.igor at gmail.com>:
> Draft:
>
> # nix-instantiate --eval --expr 'import ./fromBase64.nix
> "kjOzmCPxyw0bPciMsGSh5q+bT9g=" ==
> "9233b39823f1cb0d1b3dc88cb064a1e6af9b4fd8"' --show-trace
> true
>
> ./fromBase64.nix:
>
>
> strBase64:
>
> let
>
>   inherit (builtins) concatStringsSep stringLength substring ;
>
>   base64 = {
>     # n=0; for l in {A..Z} {a..z} {0..9} + /; do printf '"%s" = %2s; '
> $l $n; (( n++ )); (( n % 8 )) || echo; done
>     "A" =  0; "B" =  1; "C" =  2; "D" =  3; "E" =  4; "F" =  5; "G" =
> 6; "H" =  7;
>     "I" =  8; "J" =  9; "K" = 10; "L" = 11; "M" = 12; "N" = 13; "O" =
> 14; "P" = 15;
>     "Q" = 16; "R" = 17; "S" = 18; "T" = 19; "U" = 20; "V" = 21; "W" =
> 22; "X" = 23;
>     "Y" = 24; "Z" = 25; "a" = 26; "b" = 27; "c" = 28; "d" = 29; "e" =
> 30; "f" = 31;
>     "g" = 32; "h" = 33; "i" = 34; "j" = 35; "k" = 36; "l" = 37; "m" =
> 38; "n" = 39;
>     "o" = 40; "p" = 41; "q" = 42; "r" = 43; "s" = 44; "t" = 45; "u" =
> 46; "v" = 47;
>     "w" = 48; "x" = 49; "y" = 50; "z" = 51; "0" = 52; "1" = 53; "2" =
> 54; "3" = 55;
>     "4" = 56; "5" = 57; "6" = 58; "7" = 59; "8" = 60; "9" = 61; "+" =
> 62; "/" = 63;
>   };
>
>   quartet_to_int24 = q:
>     # https://en.wikipedia.org/wiki/Base64
>     let
>       s = n: assert (stringLength q == 4); substring (3 - n) 1 q;
>       d = n: base64.${s n};
>     in if s 0 != "=" then
>         64 * (64 * (64 * (d 3) + (d 2)) + (d 1)) + (d 0)
>       else if s 1 != "=" then
>         64 * (64 * (64 * (d 3) + (d 2)) + (d 1)) / 256 # right shift by 8 bits
>       else
>         64 * (64 * (64 * (d 3) + (d 2))) / 65536 # right shift by 16 bits
>       ;
>
>   int24_to_hex = i: # 16777215 (0xFFFFFF, 2^24-1) max
>     let
>       hex = "0123456789abcdef";
>       toHex = n:
>         let
>           d = n / 16;
>           r = n - 16 * d;
>         in "${if d != 0 then toHex d else ""}${substring r 1 hex}";
>     in assert (0 <= i && i <= 16777215); toHex i;
>
>   quartets = s:
>     let
>       l = stringLength s;
>       h = substring 0 4 s;
>       t = substring 4 (l - 4) s;
>     in [h] ++ (if t != "" then quartets t else []);
>
> /*
>
>   FIXME: usage of library functions like concatMapString
>   causes very cryptic errors:
>
>   # nix-instantiate --eval --expr 'import ./fromBase64.nix
> "kjOzmCPxyw0bPciMsGSh5q+bT9g="' --show-trace
>   error: while evaluating anonymous function at
> .../fromBase64.nix:1:1, called from (string):1:18:
>   value is a function while a set was expected, at .../fromBase64.nix:3:4
>
> */
>
> in concatStringsSep "" (map (x: int24_to_hex (quartet_to_int24 x))
> (quartets strBase64))
>
> 2016-10-07 16:35 GMT+03:00 Игорь Пашев <pashev.igor at gmail.com>:
>> Hi all.
>>
>> What options are there to convert a base64-encoded raw binary data
>> into "normal" hexadecimal string in Nix (during evalutation)?
>>
>> E. i. "kjOzmCPxyw0bPciMsGSh5q+bT9g=" ->
>> "9233b39823f1cb0d1b3dc88cb064a1e6af9b4fd8"
>>
>> to make it valid input for fetchurl, etc.