All parsing routines have the same signature now. #94
This commit is contained in:
John Evans
parent
40e91dae7f
commit
2b5b1d081d
1 changed files with 81 additions and 69 deletions
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@ -103,7 +103,7 @@ class Codestream(object):
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read_buffer = fptr.read(2)
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try:
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marker_id, = struct.unpack('>H', read_buffer)
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self._marker_id, = struct.unpack('>H', read_buffer)
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except struct.error:
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# Treat this as a warning.
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msg = "Marker had length {0} instead of expected length of 2 "
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@ -111,13 +111,15 @@ class Codestream(object):
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warnings.warn(msg.format(len(read_buffer)))
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break
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if marker_id == 0xff90 and header_only:
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self._offset = fptr.tell() - 2
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if self._marker_id == 0xff90 and header_only:
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# Start-of-tile (SOT) means that we are out of the main header
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# and there is no need to go further.
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break
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try:
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segment = self._process_marker_segment(fptr, marker_id)
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segment = self._process_marker_segment(fptr)
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except Exception as error:
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# Treat this as a warning.
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msg = str(error)
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@ -126,11 +128,11 @@ class Codestream(object):
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self.segment.append(segment)
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if marker_id == 0xffd9:
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if self._marker_id == 0xffd9:
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# end of codestream, should break.
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break
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if marker_id == 0xff93:
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if self._marker_id == 0xff93:
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# If SOD, then we need to seek past the tile part bit stream.
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if self._parse_tpart_flag and not header_only:
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# But first parse the tile part bit stream for SOP and
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@ -140,93 +142,126 @@ class Codestream(object):
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fptr.seek(self._tile_offset[-1] + self._tile_length[-1])
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def _process_marker_segment(self, fptr, marker_id):
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def _process_marker_segment(self, fptr):
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"""Process and return a segment from the codestream.
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"""
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offset = fptr.tell() - 2
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if self._marker_id >= 0xff30 and self._marker_id <= 0xff3f:
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segment = self._parse_reserved_marker(fptr)
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if marker_id >= 0xff30 and marker_id <= 0xff3f:
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the_id = '0x{0:x}'.format(marker_id)
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segment = Segment(marker_id=the_id, offset=offset, length=0)
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elif marker_id == 0xff51:
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elif self._marker_id == 0xff51:
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segment = self._parse_siz_segment(fptr)
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elif marker_id == 0xff52:
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elif self._marker_id == 0xff52:
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segment = self._parse_cod_segment(fptr)
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elif marker_id == 0xff53:
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elif self._marker_id == 0xff53:
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segment = self._parse_coc_segment(fptr)
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elif marker_id == 0xff55:
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elif self._marker_id == 0xff55:
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segment = self._parse_tlm_segment(fptr)
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elif marker_id == 0xff58:
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elif self._marker_id == 0xff58:
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segment = self._parse_plt_segment(fptr)
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elif marker_id == 0xff5c:
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elif self._marker_id == 0xff5c:
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segment = self._parse_qcd_segment(fptr)
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elif marker_id == 0xff5d:
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elif self._marker_id == 0xff5d:
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segment = self._parse_qcc_segment(fptr)
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elif marker_id == 0xff5e:
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elif self._marker_id == 0xff5e:
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segment = self._parse_rgn_segment(fptr)
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elif marker_id == 0xff5f:
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elif self._marker_id == 0xff5f:
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segment = self._parse_pod_segment(fptr)
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elif marker_id == 0xff60:
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elif self._marker_id == 0xff60:
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segment = self._parse_ppm_segment(fptr)
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elif marker_id == 0xff61:
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elif self._marker_id == 0xff61:
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segment = self._parse_ppt_segment(fptr)
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elif marker_id == 0xff63:
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elif self._marker_id == 0xff63:
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segment = self._parse_crg_segment(fptr)
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elif marker_id == 0xff64:
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elif self._marker_id == 0xff64:
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segment = self._parse_cme_segment(fptr)
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elif marker_id == 0xff90:
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elif self._marker_id == 0xff90:
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segment = self._parse_sot_segment(fptr)
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elif marker_id == 0xff93:
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elif self._marker_id == 0xff93:
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segment = self._parse_sod_segment(fptr)
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elif marker_id == 0xffd9:
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elif self._marker_id == 0xffd9:
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segment = self._parse_eoc_segment(fptr)
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elif marker_id in _VALID_MARKERS:
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elif self._marker_id in _VALID_MARKERS:
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# It's a reserved marker that I don't know anything about.
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# See table A-1 in ISO/IEC FCD15444-1.
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segment = _parse_generic_segment(fptr, marker_id)
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segment = self._parse_reserved_segment(fptr)
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elif ((marker_id & 0xff00) >> 8) == 255:
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# Peek ahead to see if the next two bytes are a marker or not.
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# Then seek back.
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msg = "Unrecognized marker id: 0x{0:x}".format(marker_id)
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warnings.warn(msg)
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cpos = fptr.tell()
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read_buffer = fptr.read(2)
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next_item, = struct.unpack('>H', read_buffer)
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fptr.seek(cpos)
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if ((next_item & 0xff00) >> 8) == 255:
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# No segment associated with this marker, so reset
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# to two bytes after it.
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segment = Segment(id='0x{0:x}'.format(marker_id),
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offset=offset, length=0)
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else:
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segment = _parse_generic_segment(fptr, marker_id)
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elif self._marker_id == 0xff79:
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segment = self._parse_unrecognized_segment(fptr)
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else:
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msg = 'Invalid marker id encountered at byte {0:d} '
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msg += 'in codestream: "0x{1:x}"'
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msg = msg.format(offset, marker_id)
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msg = msg.format(self._offset, self._marker_id)
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raise IOError(msg)
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return segment
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def _parse_unrecognized_segment(self, fptr):
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"""Looks like a marker, but not sure what it is.
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"""
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msg = "Unrecognized marker id: 0x{0:x}".format(self._marker_id)
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warnings.warn(msg)
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cpos = fptr.tell()
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read_buffer = fptr.read(2)
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next_item, = struct.unpack('>H', read_buffer)
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fptr.seek(cpos)
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if ((next_item & 0xff00) >> 8) == 255:
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# No segment associated with this marker, so reset
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# to two bytes after it.
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segment = Segment(id='0x{0:x}'.format(self._marker_id),
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offset=self._offset, length=0)
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else:
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segment = self._parse_reserved_segment(fptr)
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return segment
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def _parse_reserved_marker(self, fptr):
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"""Marker range between 0xff30 and 0xff39.
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"""
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the_id = '0x{0:x}'.format(self._marker_id)
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segment = Segment(marker_id=the_id, offset=self._offset, length=0)
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return segment
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def _parse_reserved_segment(self, fptr):
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"""Parse a marker segment for which we know nothing of the segment itself.
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Parameters
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----------
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fptr : file
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Open file object.
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Returns
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-------
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Segment instance.
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"""
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offset = fptr.tell() - 2
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read_buffer = fptr.read(2)
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length, = struct.unpack('>H', read_buffer)
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data = fptr.read(length-2)
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segment = Segment(marker_id='0x{0:x}'.format(self._marker_id),
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offset=offset, length=length, data=data)
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return segment
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def _parse_tile_part_bit_stream(self, fptr, sod_marker, tile_length):
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"""Parse the tile part bit stream for SOP, EPH marker segments."""
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read_buffer = fptr.read(tile_length)
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@ -1763,26 +1798,3 @@ def _print_quantization_style(sqcc):
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elif sqcc & 0x1f == 2:
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msg += 'scalar explicit, '
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return msg
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def _parse_generic_segment(fptr, marker_id):
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"""Parse a generic marker segment.
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Parameters
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----------
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fptr : file
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Open file object.
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Returns
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-------
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Segment instance.
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"""
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offset = fptr.tell() - 2
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read_buffer = fptr.read(2)
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length, = struct.unpack('>H', read_buffer)
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data = fptr.read(length-2)
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segment = Segment(marker_id='0x{0:x}'.format(marker_id), offset=offset,
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length=length, data=data)
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return segment
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