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zstd.py

ofrak_components.zstd

ZstdData (GenericBinary)

A zstd binary blob.

ZstdPacker (Packer)

Pack data into a compressed zstd file.

pack(self, resource, config=None) async

Pack the given resource.

Users should not call this method directly; rather, they should run Resource.run or Resource.pack.

Parameters:

Name Type Description Default
resource Resource required
config Optional[ofrak_components.zstd.ZstdPackerConfig]

Optional config for packing. If an implementation provides a default, this default will always be used when config would otherwise be None. Note that a copy of the default config will be passed, so the default config values cannot be modified persistently by a component run.

None
Source code in ofrak_components/zstd.py
async def pack(self, resource: Resource, config: Optional[ZstdPackerConfig] = None):
    if config is None:
        config = ZstdPackerConfig(compression_level=19)
    zstd_view = await resource.view_as(ZstdData)
    child_file = await zstd_view.get_child()
    uncompressed_data = await child_file.resource.get_data()

    with tempfile.NamedTemporaryFile() as uncompressed_file:
        uncompressed_file.write(uncompressed_data)
        uncompressed_file.flush()
        output_filename = tempfile.mktemp()

        command = ["zstd", "-T0", f"-{config.compression_level}"]
        if config.compression_level > 19:
            command.append("--ultra")
        command.extend([uncompressed_file.name, "-o", output_filename])
        try:
            subprocess.run(command, check=True)
            with open(output_filename, "rb") as f:
                result = f.read()
        except subprocess.CalledProcessError as e:
            raise PackerError(format_called_process_error(e))

        compressed_data = result
        original_size = await zstd_view.resource.get_data_length()
        resource.queue_patch(Range(0, original_size), compressed_data)

ZstdPackerConfig (ComponentConfig) dataclass

ZstdPackerConfig(compression_level: int)

ZstdUnpacker (Unpacker)

Unpack (decompress) a zstd file.

unpack(self, resource, config) async

Unpack the given resource.

Users should not call this method directly; rather, they should run Resource.run or Resource.unpack.

Parameters:

Name Type Description Default
resource Resource

The resource that is being unpacked

required
config ~CC

Optional config for unpacking. If an implementation provides a default, this default will always be used when config would otherwise be None. Note that a copy of the default config will be passed, so the default config values cannot be modified persistently by a component run.

required
Source code in ofrak_components/zstd.py
async def unpack(self, resource: Resource, config: CC) -> None:
    with tempfile.NamedTemporaryFile(suffix=".zstd") as compressed_file:
        compressed_file.write(await resource.get_data())
        compressed_file.flush()
        output_filename = tempfile.mktemp()

        command = ["zstd", "-d", "-k", compressed_file.name, "-o", output_filename]
        try:
            subprocess.run(command, check=True)
            with open(output_filename, "rb") as f:
                result = f.read()
        except subprocess.CalledProcessError as e:
            raise UnpackerError(format_called_process_error(e))

        await resource.create_child(tags=(GenericBinary,), data=result)