config/pkgs/compress-drv/default.nix

72 lines
1.9 KiB
Nix

/*
compressDrv compresses files in a given derivation.
Inputs:
- formats :: [String]
List of file extensions to compress.
Example: ["txt" "svg" "xml"]
- compressors :: [String]
A list of compressor names to use. Each element will need to have
an associated compressor in the same arguments (see below).
Example: ["gz" "zstd"]
- compressor-<EXTENSION> :: String
Map a desired extension (e.g. `gz`) to a compress program.
The compressor program that will be executed to get the `COMPRESSOR`
extension. The program should have a single " {}", which will be the
replaced with the target filename.
Compressor must:
- read symlinks (thus --force is needed to gzip, zstd, xz).
- keep the original file in place (--keep).
Example compressor:
compressor-xz = "${xz}/bin/xz --force --keep {}";
See compressDrvWeb, which is a wrapper on top of compressDrv, for broader
use examples.
*/
{
lib,
runCommand,
}: drv: {
formats,
compressors,
...
} @ args: let
validProg = ext: prog: let
matches = (builtins.length (builtins.split "\\{}" prog) - 1) / 2;
in
lib.assertMsg
(matches == 1)
"compressor-${ext} needs to have exactly one '{}', found ${builtins.toString matches}";
compressorMap = lib.filterAttrs (k: _: (lib.hasPrefix "compressor-" k)) args;
mkCmd = ext: prog:
assert validProg ext prog; ''
find -L $out -type f -regextype posix-extended -iregex '.*\.(${formatsPipe})' -print0 \
| xargs -0 -P$NIX_BUILD_CORES -I{} ${prog}
'';
formatsPipe = builtins.concatStringsSep "|" formats;
in
runCommand "${drv.name}-compressed" {} ''
mkdir $out
(cd ${drv}; find -L -type d -exec mkdir -p $out/{} ';')
(cd ${drv}; find -L -type f -exec ln -s ${drv}/{} $out/{} ';')
${
lib.concatMapStringsSep
"\n\n"
(ext: mkCmd ext (builtins.getAttr "compressor-${ext}" compressorMap))
compressors
}
''