From 8b0968b2054d3bb8d90b5ac056727f7c2ebeaed3 Mon Sep 17 00:00:00 2001
From: Igor Pashev <pashev.igor@gmail.com>
Date: Tue, 11 Dec 2018 18:10:48 +0300
Subject: (* HUGE *) Use nixpkgs overlays

---
 pkgs/jenkinsWithPlugins/fromBase64.nix | 74 ++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 pkgs/jenkinsWithPlugins/fromBase64.nix

(limited to 'pkgs/jenkinsWithPlugins/fromBase64.nix')

diff --git a/pkgs/jenkinsWithPlugins/fromBase64.nix b/pkgs/jenkinsWithPlugins/fromBase64.nix
new file mode 100644
index 0000000..3130f9c
--- /dev/null
+++ b/pkgs/jenkinsWithPlugins/fromBase64.nix
@@ -0,0 +1,74 @@
+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))
+
-- 
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