Allow customizing ZstdTarFile compression concurrency

Also turn the compressor-specific arguments into keyword-only arguments.

1 files changed, 9 insertions, 3 deletions

diff --git a/linuxnamespaces/tarutils.py b/linuxnamespaces/tarutils.py
index 3a152d6..5ad60cd 100644
--- a/linuxnamespaces/tarutils.py
+++ b/linuxnamespaces/tarutils.py
@@ -31,11 +31,15 @@ class ZstdTarFile(tarfile.TarFile):
         name: str,
         mode: typing.Literal["r", "w", "x"] = "r",
         fileobj: typing.BinaryIO | None = None,
+        *,
         compresslevel: int | None = None,
+        threads: int | None = None,
         **kwargs: typing.Any,
     ) -> tarfile.TarFile:
         """Open a zstd compressed tar archive with the given name for readin or
-        writing. Appending is not supported.
+        writing. Appending is not supported. The class allows customizing the
+        compression level and the compression concurrency (default parallel)
+        while decompression ignores those arguments.
         """
         if mode not in ("r", "w", "x"):
             raise ValueError("mode must be 'r', 'w' or 'x'")
@@ -49,17 +53,19 @@ class ZstdTarFile(tarfile.TarFile):
         if mode == "r":
             zfobj = zstandard.open(openobj, "rb")
         else:
+            if threads is None:
+                threads = -1
             if compresslevel is not None:
                 if compresslevel > 22:
                     raise ValueError(
                         "invalid compression level {compresslevel}"
                     )
                 cctx = zstandard.ZstdCompressor(
-                    write_checksum=True, threads=-1, level=compresslevel
+                    write_checksum=True, threads=threads, level=compresslevel
                 )
             else:
                 cctx = zstandard.ZstdCompressor(
-                    write_checksum=True, threads=-1
+                    write_checksum=True, threads=threads
                 )
             zfobj = zstandard.open(openobj, mode + "b", cctx=cctx)
         try: