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