def findSynchronizeBits(parser, start, max_size):
"""
Find synchronisation bits (11 bits set to 1)
Returns None on error, or number of bytes before the synchronization.
"""
address0 = parser.absolute_address
end = start + max_size
size = 0
while start < end:
# Fast search: search 0xFF (first byte of sync frame field)
length = parser.stream.searchBytesLength("\xff", False, start, end)
if length is None:
return None
size += length
start += length * 8
# Strong validation of frame: create the frame
# and call method isValid()
try:
frame = createOrphanField(parser, start - address0, Frame, "frame")
valid = frame.isValid()
except HACHOIR_ERRORS:
valid = False
if valid:
return size
# Invalid frame: continue
start += 8
size += 1
return None
def findSynchronizeBits(parser, start, max_size):
"""
Find synchronisation bits (11 bits set to 1)
Returns None on error, or number of bytes before the synchronization.
"""
address0 = parser.absolute_address
end = start + max_size
size = 0
while start < end:
# Fast search: search 0xFF (first byte of sync frame field)
length = parser.stream.searchBytesLength("\xff", False, start, end)
if length is None:
return None
size += length
start += length * 8
# Strong validation of frame: create the frame
# and call method isValid()
try:
frame = createOrphanField(parser, start-address0, Frame, "frame")
valid = frame.isValid()
except HACHOIR_ERRORS:
valid = False
if valid:
return size
# Invalid frame: continue
start += 8
size += 1
return None
def createLastPage(self):
start = self[0].size
end = MAX_FILESIZE * 8
if True:
# FIXME: This doesn't work on all files (eg. some Ogg/Theora)
offset = self.stream.searchBytes("OggS\0\5", start, end)
if offset is None:
offset = self.stream.searchBytes("OggS\0\4", start, end)
if offset is None:
return None
return createOrphanField(self, offset, OggPage, "page")
else:
# Very slow version
page = None
while True:
offset = self.stream.searchBytes("OggS\0", start, end)
if offset is None:
break
page = createOrphanField(self, offset, OggPage, "page")
start += page.size
return page
def createLastPage(self):
start = self[0].size
end = MAX_FILESIZE * 8
if True:
# FIXME: This doesn't work on all files (eg. some Ogg/Theora)
offset = self.stream.searchBytes("OggS\0\5", start, end)
if offset is None:
offset = self.stream.searchBytes("OggS\0\4", start, end)
if offset is None:
return None
return createOrphanField(self, offset, OggPage, "page")
else:
# Very slow version
page = None
while True:
offset = self.stream.searchBytes("OggS\0", start, end)
if offset is None:
break
page = createOrphanField(self, offset, OggPage, "page")
start += page.size
return page
def createContentSize(self):
# Get "frames" field
field = self[0]
if field.name != "frames":
try:
field = self[1]
except MissingField:
# File only contains ID3v1 or ID3v2
return field.size
# Error: second field are not the frames"?
if field.name != "frames":
return None
# Go to last frame
frames = field
frame = frames["frame[0]"]
address0 = field.absolute_address
size = address0 + frame.size
while True:
try:
# Parse one MPEG audio frame
frame = createOrphanField(frames, size - address0, Frame,
"frame")
# Check frame 32 bits header
if not frame.isValid():
break
except HACHOIR_ERRORS:
break
if MAX_FILESIZE < (size + frame.size):
break
size += frame.size
# ID3v1 at the end?
try:
if self.stream.readBytes(size, 3) == "TAG":
size += ID3v1.static_size
except InputStreamError:
pass
return size
def createContentSize(self):
# Get "frames" field
field = self[0]
if field.name != "frames":
try:
field = self[1]
except MissingField:
# File only contains ID3v1 or ID3v2
return field.size
# Error: second field are not the frames"?
if field.name != "frames":
return None
# Go to last frame
frames = field
frame = frames["frame[0]"]
address0 = field.absolute_address
size = address0 + frame.size
while True:
try:
# Parse one MPEG audio frame
frame = createOrphanField(frames, size - address0, Frame, "frame")
# Check frame 32 bits header
if not frame.isValid():
break
except HACHOIR_ERRORS:
break
if MAX_FILESIZE < (size + frame.size):
break
size += frame.size
# ID3v1 at the end?
try:
if self.stream.readBytes(size, 3) == "TAG":
size += ID3v1.static_size
except InputStreamError:
pass
return size
