How to merge two tar gz BinaryIO in Python 3

Question

I have two Binary I/O stream (both inherit of BufferedIOBase), which represent two tar archives compressed with gzip algorithm.

Is there any effecient way to create a third one which is the combination of the two others ?

I tried by converting both stream to tarfile.Tarfile through the fileobj arguments and adding each member to a third one :

def merge_environment(a: Optional[BinaryIO], b: Optional[BinaryIO]) -> Optional[BinaryIO]:
    """Merge <a> and <b>, returning a new tarfile.TarFile object.

    If two files in <a> and <b> have the same name, the one in <a> prevails."""
    destio = io.BytesIO()

    with tarfile.open(fileobj=a, mode="r:gz") as t1, \
            tarfile.open(fileobj=b, mode="r:gz") as t2, \
            tarfile.open(fileobj=destio, mode="w:gz") as dest:

        t1_members = [m for m in t1.getmembers() if m.name != ""]
        t1_names = [m.name for m in t1.members]
        t2_members = [m for m in t1.getmembers() if m.name != "" and m.name not in t1_names]

        for member in t1_members:
            dest.addfile(member, t1.extractfile(member))
        for member in t2_members:
            dest.addfile(member, t2.extractfile(member))

    destio.seek(0, 0)
    return destio

But this doesn't work if any of the tar.gz contain directory since tarfile.extractfile() does not work on directory.

Any solution ?

Answer 1

The solution was quite simple, fileobj argument of tarfile.addfile is not mandatory, tarinfo is enough :

destio = io.bytesIO()
with tarfile.open(fileobj=a, mode="r:gz") as t1, \
        tarfile.open(fileobj=b, mode="r:gz") as t2, \
        tarfile.open(fileobj=destio, mode="w:gz") as dest:

    t1_members = [m for m in t1.getmembers()]
    t1_names = t1.getnames()
    t2_members = [m for m in t2.getmembers() if m.name not in t1_names]

    for member in t1_members:
        if member.isdir():
            dest.addfile(member)
        else:
            dest.addfile(member, t1.extractfile(member))

    for member in t2_members:
        if member.isdir():
            dest.addfile(member)
        else:
            dest.addfile(member, t2.extractfile(member))