lib: import generally useful stuff from genipv6

1 files changed, 27 insertions, 0 deletions

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