def _get_offset_endian_jpeg(f):
## it's a JPEG file
logger.debug("JPEG format recognized data[0:2] == '0xFFD8'.")
## Determine the "base" from which to start reading
f.seek(0)
data = bytearray(f.read(12))
base = 2
while data[2] == 0xFF and data[6:10] in ('JFIF', 'JFXX', 'OLYM', 'Phot'):
logger.debug(" data[2] == 0xFF data[3] == {:x} and data[6:10] = {}"
"".format(data[3], data[6:10]))
length = (data[4] * 256) + data[5]
assert isinstance(length, int)
logger.debug(" Length offset is {:d}".format(length))
f.read(length - 8)
## Fake an EXIF beginning of file
## I don't think this is used. --gd
data = '\xFF\x00' + f.read(10)
#fake_exif = 1
if base > 2:
base += length + 2
else:
base = length + 4
logger.debug(" Set segment base to {}".format(base))
del data # We're done with it!!
b = mmapbytes(f)
while True:
logger.debug("Segment base 0x{:X}".format(base))
b.set_window(base)
b1 = b[1]
if b[0] == 0xFF:
if b1 == 0xE1:
if b[4:8] == "Exif":
base -= 2
break
if b1 == 0xDB:
break
_base_increment = (b[2] * 256) + b[3] + 2
logger.debug("Increment base by {}".format(_base_increment))
base += _base_increment
## Jump ahead after file headers
b.set_window(base)
_data_b2 = b[2]
_data_b6t10 = b[6:10]
_data_b6t11 = b[6:11]
if _data_b2 == 0xFF:
logger.debug("Exif header: {:x} {!r}".format(_data_b2, _data_b6t11))
if _data_b6t10 == 'Exif':
## detected EXIF header
offset = f.tell()
endian = f.read(1)
return offset, endian
#HACK TEST: endian = 'M'
elif _data_b6t11 == 'Ducky':
## detected Ducky header.
logger.debug("EXIF-like header (normally 0xFF and code): "
"{:x} and {!r}".format(_data_b2, _data_b6t11))
offset = f.tell()
endian = f.read(1)
return offset, endian
elif _data_b6t11 == 'Adobe':
## detected APP14 (Adobe)
logger.debug("EXIF-like header (normally 0xFF and code): "
"{:x} and {!r}".format(_data_b2, _data_b6t11))
offset = f.tell()
endian = f.read(1)
return offset, endian
else:
## No EXIF information found -- error!!
logger.debug(
"No EXIF header found:\n"
" Expected b[2]==0xFF and b[6:10]=='Exif'' (or 'Duck')\n"
" Got: {:x} and {!r}".format(_data_b2, _data_b6t11))
raise NoExifData("No EXIF header found")
def test_mmapbytes(self):
from StringIO import StringIO
from exifpy.utils import mmapbytes
message = "Hello, world; spam & eggs for everybody!"
## Test direct referencing of items
## The object should behave exactly like a bytearray
test_indices = [0, 7, 14, -1, -10, -14]
test_windows = [
(None, None),
(0, 0),
(0, 12),
(None, 12),
# (14, 0), ## Invalid!!
(14, None),
(14, 25),
]
for winStart, winEnd in test_windows:
_message = message[winStart:winEnd]
mm = mmapbytes(StringIO(message), winStart, winEnd)
for idx in test_indices:
try:
expected = ord(_message[idx])
except IndexError:
# print "\n\n\nWe're running with window {},{}" \
# "".format(winStart, winEnd)
# print "The string {!r} raised IndexError on index {}. "\
# "We expect the mmapbytes() object to do the same."\
# "".format(_message, idx)
with self.assertRaises(IndexError):
mm[idx]
# print "RETURNED {!r}".format(mm[idx])
else:
result = mm[idx]
self.assertEqual(
expected,
result,
"Test window {},{} index {} - Expected: {!r} got: {!r}"
"".format(winStart, winEnd, idx, expected, result),
)
## Test some slicing.
## The object should behave exactly like a string.
test_indices = [(0, 1), (0, 10), (0, None), (None, 0), (None, 10), (10, None), (None, None)]
test_windows = [
(None, None),
(0, 0),
(0, 12),
(None, 12),
# (14, 0), # Invalid!
(14, None),
(14, 25),
]
for winStart, winEnd in test_windows:
_message = message[winStart:winEnd]
mm = mmapbytes(StringIO(message), winStart, winEnd)
for start, end in test_indices:
expected = _message[start:end]
result = mm[start:end]
self.assertEqual(
expected,
result,
"Test window {},{} slice {},{} - Expected: {!r} got: {!r}"
"".format(winStart, winEnd, start, end, expected, result),
)
