From 474e3e2e4513a5d2df89789885725b176e7ec532 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Tue, 11 Dec 2018 23:21:42 +0100
Subject: lib: import generally useful stuff from genipv6

---
 lib/default.nix | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'lib/default.nix')

diff --git a/lib/default.nix b/lib/default.nix
index e352c7be..64b2d48a 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -112,6 +112,33 @@ let
             (if test ".*::.*" a
               then a
               else group-zeros (drop-leading-zeros a));
+
+    hashToLength = n: s: substring 0 n (hashString "sha256" s);
+
+    dropLast = n: xs: reverseList (drop n (reverseList xs));
+    takeLast = n: xs: reverseList (take n (reverseList xs));
+
+    # Split string into list of chunks where each chunk is at most n chars long.
+    # The leftmost chunk might shorter.
+    # Example: stringToGroupsOf "123456" -> ["12" "3456"]
+    stringToGroupsOf = n: s: let
+      acc =
+        foldl'
+          (acc: c: if stringLength acc.chunk < n then {
+            chunk = acc.chunk + c;
+            chunks = acc.chunks;
+          } else {
+            chunk = c;
+            chunks = acc.chunks ++ [acc.chunk];
+          })
+          {
+            chunk = "";
+            chunks = [];
+          }
+          (stringToCharacters s);
+    in
+      filter (x: x != []) ([acc.chunk] ++ acc.chunks);
+
   };
 in
 
-- 
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