uvms/pkgs/writeErofs/package.nix

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{
lib,
erofs-utils,
runCommand,
python3Minimal,
bubblewrap,
writeClosure,
}:
{
name ? "${label}.erofs",
label ? "image",
roots ? [ ],
rootsExclude ? [ ],
erofsArgs ? [
"--mount-point=/nix/store"
"-z"
"lz4hc,level=3"
"-T0"
"-L"
label
"--all-root"
],
...
}@attrs:
let
old = writeClosure rootsExclude;
new = writeClosure roots;
attrs' = lib.removeAttrs [ "name" "roots" "rootsExclude" "erofsArgs" ] attrs;
in
runCommand name
(
attrs
// {
__structuredAttrs = true;
inherit name label;
unsafeDiscardReferences.out = true;
nativeBuildInputs = [
erofs-utils
bubblewrap
python3Minimal
]
++ attrs.nativeBuildInputs or [ ];
inherit old new erofsArgs;
}
)
''
mkdir -p store
python3 << EOF
import hashlib, json, os, subprocess
from uuid import UUID
def uuid_from_node(node: int = 0) -> UUID:
return UUID(fields=(*((0,) * 5), node))
out_path = os.environ.get("out")
default_uuid = uuid_from_node((2**48 - 1) & int.from_bytes(hashlib.sha256(out_path.encode("ascii")).digest()))
with open(os.environ.get("NIX_ATTRS_JSON_FILE"), mode="r") as f:
attrs = json.load(f)
name = attrs["name"]
with open(attrs["old"], mode="r") as f:
old_paths = set(ln.rstrip() for ln in f)
with open(attrs["new"], mode="r") as f:
new_paths = [ln.rstrip() for ln in f]
new_paths = [p for p in new_paths if p not in old_paths]
erofs_args = attrs.get("erofsArgs", [])
if not any(a.startswith("-U") for a in erofs_args):
erofs_args.extend(["-U", str(default_uuid)])
subprocess.run(
check=True,
env=os.environ,
args=[
"bwrap",
"--dev-bind", "/", "/",
"--chdir", os.getcwd(),
*[a for p in new_paths for a in [f"--ro-bind", p, f"{os.getcwd()}/store/{os.path.basename(p)}"]],
"--",
"mkfs.erofs", *attrs.get("erofsArgs", []), out_path, "store",
],
)
EOF
''