def write(self):
"""Return a string encoding of the page header and data.
A ValueError is raised if the data is too big to fit in a
single page.
"""
data = [
struct.pack("<4sBBqIIi", b"OggS", self.version, self.__type_flags,
self.position, self.serial, self.sequence, 0)
]
lacing_data = []
for datum in self.packets:
quot, rem = divmod(len(datum), 255)
lacing_data.append(b"\xff" * quot + chr_(rem))
lacing_data = b"".join(lacing_data)
if not self.complete and lacing_data.endswith(b"\x00"):
lacing_data = lacing_data[:-1]
data.append(chr_(len(lacing_data)))
data.append(lacing_data)
data.extend(self.packets)
data = b"".join(data)
# Python's CRC is swapped relative to Ogg's needs.
# crc32 returns uint prior to py2.6 on some platforms, so force uint
crc = (~zlib.crc32(data.translate(cdata.bitswap), -1)) & 0xffffffff
# Although we're using to_uint_be, this actually makes the CRC
# a proper le integer, since Python's CRC is byteswapped.
crc = cdata.to_uint_be(crc).translate(cdata.bitswap)
data = data[:22] + crc + data[26:]
return data
def __update_parents(self, fileobj, path, delta):
"""Update all parent atoms with the new size."""
if delta == 0:
return
for atom in path:
fileobj.seek(atom.offset)
size = cdata.uint_be(fileobj.read(4))
if size == 1: # 64bit
# skip name (4B) and read size (8B)
size = cdata.ulonglong_be(fileobj.read(12)[4:])
fileobj.seek(atom.offset + 8)
fileobj.write(cdata.to_ulonglong_be(size + delta))
else: # 32bit
fileobj.seek(atom.offset)
fileobj.write(cdata.to_uint_be(size + delta))
def __update_parents(self, fileobj, path, delta):
"""Update all parent atoms with the new size."""
if delta == 0:
return
for atom in path:
fileobj.seek(atom.offset)
size = cdata.uint_be(fileobj.read(4))
if size == 1: # 64bit
# skip name (4B) and read size (8B)
size = cdata.ulonglong_be(fileobj.read(12)[4:])
fileobj.seek(atom.offset + 8)
fileobj.write(cdata.to_ulonglong_be(size + delta))
else: # 32bit
fileobj.seek(atom.offset)
fileobj.write(cdata.to_uint_be(size + delta))
