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import struct
import mutagen
import mutagen.asf
from mediafile.utils import Image
from .base import ListStorageStyle
def _unpack_asf_image(data):
"""Unpack image data from a WM/Picture tag. Return a tuple
containing the MIME type, the raw image data, a type indicator, and
the image's description.
This function is treated as "untrusted" and could throw all manner
of exceptions (out-of-bounds, etc.). We should clean this up
sometime so that the failure modes are well-defined.
"""
type, size = struct.unpack_from("<bi", data)
pos = 5
mime = b""
while data[pos : pos + 2] != b"\x00\x00":
mime += data[pos : pos + 2]
pos += 2
pos += 2
description = b""
while data[pos : pos + 2] != b"\x00\x00":
description += data[pos : pos + 2]
pos += 2
pos += 2
image_data = data[pos : pos + size]
return (mime.decode("utf-16-le"), image_data, type, description.decode("utf-16-le"))
def _pack_asf_image(mime, data, type=3, description=""):
"""Pack image data for a WM/Picture tag."""
tag_data = struct.pack("<bi", type, len(data))
tag_data += mime.encode("utf-16-le") + b"\x00\x00"
tag_data += description.encode("utf-16-le") + b"\x00\x00"
tag_data += data
return tag_data
class ASFStorageStyle(ListStorageStyle):
"""A general storage style for Windows Media/ASF files."""
formats = ["ASF"]
def deserialize(self, data):
if isinstance(data, mutagen.asf.ASFBaseAttribute):
data = data.value
return data
class ASFImageStorageStyle(ListStorageStyle):
"""Store images packed into Windows Media/ASF byte array attributes.
Values are `Image` objects.
"""
formats = ["ASF"]
def __init__(self):
super().__init__(key="WM/Picture")
def deserialize(self, asf_picture):
mime, data, type, desc = _unpack_asf_image(asf_picture.value)
return Image(data, desc=desc, type=type)
def serialize(self, image):
pic = mutagen.asf.ASFByteArrayAttribute()
pic.value = _pack_asf_image(
image.mime_type,
image.data,
type=image.type_index,
description=image.desc or "",
)
return pic
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