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Better struct module usage #128

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Better struct module usage #128

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0209134
Better struct module usage
homm Jan 19, 2022
e8d540a
unused
homm Jan 19, 2022
f00f031
useless branches
homm Jan 19, 2022
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144 changes: 55 additions & 89 deletions piexif/_load.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import struct
import sys
from struct import unpack_from

from ._common import *
from ._exceptions import InvalidImageDataError
Expand Down Expand Up @@ -34,8 +34,8 @@ def load(input_data, key_is_name=False):
else:
exifReader.endian_mark = ">"

pointer = struct.unpack(exifReader.endian_mark + "L",
exifReader.tiftag[4:8])[0]
pointer = unpack_from(exifReader.endian_mark + "L",
exifReader.tiftag, 4)[0]
exif_dict["0th"] = exifReader.get_ifd_dict(pointer, "0th")
first_ifd_pointer = exif_dict["0th"].pop("first_ifd_pointer")
if ImageIFD.ExifTag in exif_dict["0th"]:
Expand All @@ -48,8 +48,8 @@ def load(input_data, key_is_name=False):
pointer = exif_dict["Exif"][ExifIFD.InteroperabilityTag]
exif_dict["Interop"] = exifReader.get_ifd_dict(pointer, "Interop")
if first_ifd_pointer != b"\x00\x00\x00\x00":
pointer = struct.unpack(exifReader.endian_mark + "L",
first_ifd_pointer)[0]
pointer = unpack_from(exifReader.endian_mark + "L",
first_ifd_pointer)[0]
exif_dict["1st"] = exifReader.get_ifd_dict(pointer, "1st")
if (ImageIFD.JPEGInterchangeFormat in exif_dict["1st"] and
ImageIFD.JPEGInterchangeFormatLength in exif_dict["1st"]):
Expand Down Expand Up @@ -105,32 +105,25 @@ def __init__(self, data):

def get_ifd_dict(self, pointer, ifd_name, read_unknown=False):
ifd_dict = {}
tag_count = struct.unpack(self.endian_mark + "H",
self.tiftag[pointer: pointer+2])[0]
tag_count = unpack_from(self.endian_mark + "H",
self.tiftag, pointer)[0]
offset = pointer + 2
if ifd_name in ["0th", "1st"]:
t = "Image"
else:
t = ifd_name
p_and_value = []
for x in range(tag_count):
pointer = offset + 12 * x
tag = struct.unpack(self.endian_mark + "H",
self.tiftag[pointer: pointer+2])[0]
value_type = struct.unpack(self.endian_mark + "H",
self.tiftag[pointer + 2: pointer + 4])[0]
value_num = struct.unpack(self.endian_mark + "L",
self.tiftag[pointer + 4: pointer + 8]
)[0]
tag, value_type, value_num = unpack_from(
self.endian_mark + "HHL", self.tiftag, pointer)
value = self.tiftag[pointer+8: pointer+12]
p_and_value.append((pointer, value_type, value_num, value))
v_set = (value_type, value_num, value, tag)
if tag in TAGS[t]:
ifd_dict[tag] = self.convert_value(v_set)
elif read_unknown:
ifd_dict[tag] = (v_set[0], v_set[1], v_set[2], self.tiftag)
#else:
# pass
else:
pass

if ifd_name == "0th":
pointer = offset + 12 * tag_count
Expand All @@ -145,108 +138,81 @@ def convert_value(self, val):

if t == TYPES.Byte: # BYTE
if length > 4:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack("B" * length,
self.tiftag[pointer: pointer + length])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from("B" * length, self.tiftag, pointer)
else:
data = struct.unpack("B" * length, value[0:length])
data = unpack_from("B" * length, value)
elif t == TYPES.Ascii: # ASCII
if length > 4:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = self.tiftag[pointer: pointer+length - 1]
else:
data = value[0: length - 1]
elif t == TYPES.Short: # SHORT
if length > 2:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "H" * length,
self.tiftag[pointer: pointer+length*2])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "H" * length,
self.tiftag, pointer)
else:
data = struct.unpack(self.endian_mark + "H" * length,
value[0:length * 2])
data = unpack_from(self.endian_mark + "H" * length, value)
elif t == TYPES.Long: # LONG
if length > 1:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "L" * length,
self.tiftag[pointer: pointer+length*4])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "L" * length,
self.tiftag, pointer)
else:
data = struct.unpack(self.endian_mark + "L" * length,
value)
data = unpack_from(self.endian_mark + "L" * length, value)
elif t == TYPES.Rational: # RATIONAL
pointer = struct.unpack(self.endian_mark + "L", value)[0]
if length > 1:
data = tuple(
(struct.unpack(self.endian_mark + "L",
self.tiftag[pointer + x * 8:
pointer + 4 + x * 8])[0],
struct.unpack(self.endian_mark + "L",
self.tiftag[pointer + 4 + x * 8:
pointer + 8 + x * 8])[0])
for x in range(length)
)
else:
data = (struct.unpack(self.endian_mark + "L",
self.tiftag[pointer: pointer + 4])[0],
struct.unpack(self.endian_mark + "L",
self.tiftag[pointer + 4: pointer + 8]
)[0])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = tuple(
unpack_from(self.endian_mark + "LL",
self.tiftag, pointer + x * 8)
for x in range(length)
)
elif t == TYPES.SByte: # SIGNED BYTES
if length > 4:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack("b" * length,
self.tiftag[pointer: pointer + length])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from("b" * length, self.tiftag, pointer)
else:
data = struct.unpack("b" * length, value[0:length])
data = unpack_from("b" * length, value)
elif t == TYPES.Undefined: # UNDEFINED BYTES
if length > 4:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = self.tiftag[pointer: pointer+length]
else:
data = value[0:length]
data = value[0: length]
elif t == TYPES.SShort: # SIGNED SHORT
if length > 2:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "h" * length,
self.tiftag[pointer: pointer+length*2])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "h" * length,
self.tiftag, pointer)
else:
data = struct.unpack(self.endian_mark + "h" * length,
value[0:length * 2])
data = unpack_from(self.endian_mark + "h" * length, value)
elif t == TYPES.SLong: # SLONG
if length > 1:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "l" * length,
self.tiftag[pointer: pointer+length*4])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "l" * length,
self.tiftag, pointer)
else:
data = struct.unpack(self.endian_mark + "l" * length,
value)
data = unpack_from(self.endian_mark + "l" * length, value)
elif t == TYPES.SRational: # SRATIONAL
pointer = struct.unpack(self.endian_mark + "L", value)[0]
if length > 1:
data = tuple(
(struct.unpack(self.endian_mark + "l",
self.tiftag[pointer + x * 8: pointer + 4 + x * 8])[0],
struct.unpack(self.endian_mark + "l",
self.tiftag[pointer + 4 + x * 8: pointer + 8 + x * 8])[0])
for x in range(length)
)
else:
data = (struct.unpack(self.endian_mark + "l",
self.tiftag[pointer: pointer + 4])[0],
struct.unpack(self.endian_mark + "l",
self.tiftag[pointer + 4: pointer + 8]
)[0])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = tuple(
unpack_from(self.endian_mark + "ll",
self.tiftag, pointer + x * 8)
for x in range(length)
)
elif t == TYPES.Float: # FLOAT
if length > 1:
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "f" * length,
self.tiftag[pointer: pointer+length*4])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "f" * length,
self.tiftag, pointer)
else:
data = struct.unpack(self.endian_mark + "f" * length,
value)
data = unpack_from(self.endian_mark + "f" * length, value)
elif t == TYPES.DFloat: # DOUBLE
pointer = struct.unpack(self.endian_mark + "L", value)[0]
data = struct.unpack(self.endian_mark + "d" * length,
self.tiftag[pointer: pointer+length*8])
pointer = unpack_from(self.endian_mark + "L", value)[0]
data = unpack_from(self.endian_mark + "d" * length,
self.tiftag, pointer)
else:
raise ValueError("Exif might be wrong. Got incorrect value " +
"type to decode.\n" +
Expand Down