diff options
author | tv <tv@krebsco.de> | 2016-10-20 20:21:59 +0200 |
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committer | tv <tv@krebsco.de> | 2016-10-20 20:21:59 +0200 |
commit | 844d347ce7cf0b7646e9ecba3fbdc0b90e608501 (patch) | |
tree | 32827cb69265c117abee1654ae6cf581a9a5c87c /lib/genid.nix | |
parent | 91d6bd66f4d50d47692f55c16bfb14bdf4837520 (diff) |
lib: import bulk of krebs/4lib
Diffstat (limited to 'lib/genid.nix')
-rw-r--r-- | lib/genid.nix | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/lib/genid.nix b/lib/genid.nix new file mode 100644 index 000000000..0aed1d351 --- /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 |