From 844d347ce7cf0b7646e9ecba3fbdc0b90e608501 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Thu, 20 Oct 2016 20:21:59 +0200
Subject: lib: import bulk of krebs/4lib

---
 lib/genid.nix | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 lib/genid.nix

(limited to 'lib/genid.nix')

diff --git a/lib/genid.nix b/lib/genid.nix
new file mode 100644
index 00000000..0aed1d35
--- /dev/null
+++ b/lib/genid.nix
@@ -0,0 +1,37 @@
+{ lib, ... }:
+with lib;
+with builtins;
+let out = genid;
+
+  # id = genid s = (hash s + min) % max
+  # min <= genid s < max
+  #
+  # min = 2^24 =   16777216 = 0x001000000
+  # max = 2^32 = 4294967296 = 0x100000000
+  #
+  # id is bigger than UID of nobody and GID of nogroup
+  # see <nixos/modules/misc/ids.nix> and some spare for stuff like lxd.
+  #
+  # :: str -> uint32
+  genid = s: sum16 (addmod16_16777216 (hash s));
+
+  # :: str -> list8 uint4
+  hash = s:
+    map hexint (stringToCharacters (substring 32 8 (hashString "sha1" s)));
+
+  # :: list uint -> uint
+  sum16 = foldl (a: i: a * 16 + i) 0;
+
+  # :: list8 uint4 -> list1 uint8 ++ list6 uint4
+  addmod16_16777216 = x: let
+    a = 16 * head x + head (tail x);
+    d = tail (tail x);
+  in [(mod (a + 1) 256)] ++ d;
+
+  # :: char -> uint4
+  hexint = x: hexvals.${toLower x};
+
+  # :: attrset char uint4
+  hexvals = listToAttrs (imap (i: c: { name = c; value = i - 1; })
+                        (stringToCharacters "0123456789abcdef"));
+in out
-- 
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