tvl-depot/tools/nixery/group-layers/popcount.nix

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{ pkgs ? import <nixpkgs> { config.allowUnfree = false; }
, target }:
let
inherit (pkgs) coreutils runCommand writeText;
inherit (builtins) replaceStrings readFile toFile fromJSON toJSON foldl' listToAttrs;
path = [ pkgs."${target}" ];
# graphJSON abuses feature in Nix that makes structured runtime
# closure information available to builders. This data is imported
# back via IFD to process it for layering data.
graphJSON =
path:
runCommand "build-graph" {
__structuredAttrs = true;
exportReferencesGraph.graph = path;
PATH = "${coreutils}/bin";
builder = toFile "builder" ''
. .attrs.sh
cat .attrs.json > ''${outputs[out]}
'';
} "";
buildClosures = paths: (fromJSON (readFile (graphJSON paths)));
buildGraph = paths: listToAttrs (map (c: {
name = c.path;
value = {
inherit (c) closureSize references;
};
}) (buildClosures paths));
# Nix does not allow attrbute set keys to refer to store paths, but
# we need them to for the purpose of the calculation. To work around
# it, the store path prefix is replaced with the string 'closure/'
# and later replaced again.
fromStorePath = replaceStrings [ "/nix/store" ] [ "closure/" ];
toStorePath = replaceStrings [ "closure/" ] [ "/nix/store/" ];
buildTree = paths:
let
graph = buildGraph paths;
top = listToAttrs (map (p: {
name = fromStorePath (toString p);
value = {};
}) paths);
in top;
outputJson = thing: writeText "the-thing.json" (builtins.toJSON thing);
in outputJson (buildClosures path).graph