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from typing import BinaryIO
from exifread.utils import ord_
from exifread.exif_log import get_logger
from exifread.exceptions import InvalidExif
logger = get_logger()
def _increment_base(data, base):
return ord_(data[base + 2]) * 256 + ord_(data[base + 3]) + 2
def _get_initial_base(fh: BinaryIO, data, fake_exif) -> tuple:
base = 2
logger.debug("data[2]=0x%X data[3]=0x%X data[6:10]=%s", ord_(data[2]), ord_(data[3]), data[6:10])
while ord_(data[2]) == 0xFF and data[6:10] in (b"JFIF", b"JFXX", b"OLYM", b"Phot"):
length = ord_(data[4]) * 256 + ord_(data[5])
logger.debug(" Length offset is %s", length)
fh.read(length - 8)
# fake an EXIF beginning of file
# I don't think this is used. --gd
data = b"\xFF\x00" + fh.read(10)
fake_exif = 1
if base > 2:
logger.debug(" Added to base")
base = base + length + 4 - 2
else:
logger.debug(" Added to zero")
base = length + 4
logger.debug(" Set segment base to 0x%X", base)
return base, fake_exif
def _get_base(base, data) -> int:
# pylint: disable=too-many-statements
while True:
logger.debug(" Segment base 0x%X", base)
if data[base : base + 2] == b"\xFF\xE1":
# APP1
logger.debug(" APP1 at base 0x%X", base)
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug(" Code: %s", data[base + 4 : base + 8])
if data[base + 4 : base + 8] == b"Exif":
logger.debug(" Decrement base by 2 to get to pre-segment header (for compatibility with later code)")
base -= 2
break
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
elif data[base : base + 2] == b"\xFF\xE0":
# APP0
logger.debug(" APP0 at base 0x%X", base)
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug(" Code: %s", data[base + 4 : base + 8])
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
elif data[base : base + 2] == b"\xFF\xE2":
# APP2
logger.debug(" APP2 at base 0x%X", base)
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug(" Code: %s", data[base + 4 : base + 8])
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
elif data[base : base + 2] == b"\xFF\xEE":
# APP14
logger.debug(" APP14 Adobe segment at base 0x%X", base)
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug(" Code: %s", data[base + 4 : base + 8])
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
logger.debug(" There is useful EXIF-like data here, but we have no parser for it.")
elif data[base : base + 2] == b"\xFF\xDB":
logger.debug(" JPEG image data at base 0x%X No more segments are expected.", base)
break
elif data[base : base + 2] == b"\xFF\xD8":
# APP12
logger.debug(" FFD8 segment at base 0x%X", base)
logger.debug(
" Got 0x%X 0x%X and %s instead", ord_(data[base]), ord_(data[base + 1]), data[4 + base : 10 + base]
)
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug(" Code: %s", data[base + 4 : base + 8])
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
elif data[base : base + 2] == b"\xFF\xEC":
# APP12
logger.debug(" APP12 XMP (Ducky) or Pictureinfo segment at base 0x%X", base)
logger.debug(" Got 0x%X and 0x%X instead", ord_(data[base]), ord_(data[base + 1]))
logger.debug(" Length: 0x%X 0x%X", ord_(data[base + 2]), ord_(data[base + 3]))
logger.debug("Code: %s", data[base + 4 : base + 8])
increment = _increment_base(data, base)
logger.debug(" Increment base by %s", increment)
base += increment
logger.debug(
" There is useful EXIF-like data here (quality, comment, copyright), " "but we have no parser for it."
)
else:
try:
increment = _increment_base(data, base)
logger.debug(" Got 0x%X and 0x%X instead", ord_(data[base]), ord_(data[base + 1]))
except IndexError as err:
raise InvalidExif("Unexpected/unhandled segment type or file content.") from err
else:
logger.debug(" Increment base by %s", increment)
base += increment
return base
def find_jpeg_exif(fh: BinaryIO, data, fake_exif) -> tuple:
logger.debug("JPEG format recognized data[0:2]=0x%X%X", ord_(data[0]), ord_(data[1]))
base, fake_exif = _get_initial_base(fh, data, fake_exif)
# Big ugly patch to deal with APP2 (or other) data coming before APP1
fh.seek(0)
# in theory, this could be insufficient since 64K is the maximum size--gd
data = fh.read(base + 4000)
base = _get_base(base, data)
fh.seek(base + 12)
if ord_(data[2 + base]) == 0xFF and data[6 + base : 10 + base] == b"Exif":
# detected EXIF header
offset = fh.tell()
endian = fh.read(1)
# HACK TEST: endian = 'M'
elif ord_(data[2 + base]) == 0xFF and data[6 + base : 10 + base + 1] == b"Ducky":
# detected Ducky header.
logger.debug(
"EXIF-like header (normally 0xFF and code): 0x%X and %s",
ord_(data[2 + base]),
data[6 + base : 10 + base + 1],
)
offset = fh.tell()
endian = fh.read(1)
elif ord_(data[2 + base]) == 0xFF and data[6 + base : 10 + base + 1] == b"Adobe":
# detected APP14 (Adobe)
logger.debug(
"EXIF-like header (normally 0xFF and code): 0x%X and %s",
ord_(data[2 + base]),
data[6 + base : 10 + base + 1],
)
offset = fh.tell()
endian = fh.read(1)
else:
# no EXIF information
msg = "No EXIF header expected data[2+base]==0xFF and data[6+base:10+base]===Exif (or Duck)"
msg += "Did get 0x%X and %s" % (ord_(data[2 + base]), data[6 + base : 10 + base + 1])
raise InvalidExif(msg)
return offset, endian, fake_exif
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