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#! /usr/bin/env python3
import string
import struct
import sys
class FileExtract:
'''Decode binary data from a file'''
def __init__(self, f, b='='):
'''Initialize with an open binary file and optional byte order'''
self.file = f
self.byte_order = b
self.offsets = list()
def set_byte_order(self, b):
'''Set the byte order, valid values are "big", "little", "swap", "native", "<", ">", "@", "="'''
if b == 'big':
self.byte_order = '>'
elif b == 'little':
self.byte_order = '<'
elif b == 'swap':
# swap what ever the current byte order is
self.byte_order = swap_unpack_char()
elif b == 'native':
self.byte_order = '='
elif b == '<' or b == '>' or b == '@' or b == '=':
self.byte_order = b
else:
print("error: invalid byte order specified: '%s'" % b)
def is_in_memory(self):
return False
def seek(self, offset, whence=0):
if self.file:
return self.file.seek(offset, whence)
raise ValueError
def tell(self):
if self.file:
return self.file.tell()
raise ValueError
def read_size(self, byte_size):
s = self.file.read(byte_size)
if len(s) != byte_size:
return None
return s
def push_offset_and_seek(self, offset):
'''Push the current file offset and seek to "offset"'''
self.offsets.append(self.file.tell())
self.file.seek(offset, 0)
def pop_offset_and_seek(self):
'''Pop a previously pushed file offset, or do nothing if there were no previously pushed offsets'''
if len(self.offsets) > 0:
self.file.seek(self.offsets.pop())
def get_sint8(self, fail_value=0):
'''Extract a single int8_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(1)
if s:
v, = struct.unpack(self.byte_order + 'b', s)
return v
else:
return fail_value
def get_uint8(self, fail_value=0):
'''Extract a single uint8_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(1)
if s:
v, = struct.unpack(self.byte_order + 'B', s)
return v
else:
return fail_value
def get_sint16(self, fail_value=0):
'''Extract a single int16_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(2)
if s:
v, = struct.unpack(self.byte_order + 'h', s)
return v
else:
return fail_value
def get_uint16(self, fail_value=0):
'''Extract a single uint16_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(2)
if s:
v, = struct.unpack(self.byte_order + 'H', s)
return v
else:
return fail_value
def get_sint32(self, fail_value=0):
'''Extract a single int32_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(4)
if s:
v, = struct.unpack(self.byte_order + 'i', s)
return v
else:
return fail_value
def get_uint32(self, fail_value=0):
'''Extract a single uint32_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(4)
if s:
v, = struct.unpack(self.byte_order + 'I', s)
return v
else:
return fail_value
def get_sint64(self, fail_value=0):
'''Extract a single int64_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(8)
if s:
v, = struct.unpack(self.byte_order + 'q', s)
return v
else:
return fail_value
def get_uint64(self, fail_value=0):
'''Extract a single uint64_t from the binary file at the current file position, returns a single integer'''
s = self.read_size(8)
if s:
v, = struct.unpack(self.byte_order + 'Q', s)
return v
else:
return fail_value
def get_fixed_length_c_string(
self,
n,
fail_value='',
isprint_only_with_space_padding=False):
'''Extract a single fixed length C string from the binary file at the current file position, returns a single C string'''
s = self.read_size(n)
if s:
cstr, = struct.unpack(self.byte_order + ("%i" % n) + 's', s)
# Strip trialing NULLs
cstr = string.strip(cstr, "\0")
if isprint_only_with_space_padding:
for c in cstr:
if c in string.printable or ord(c) == 0:
continue
return fail_value
return cstr
else:
return fail_value
def get_c_string(self):
'''Extract a single NULL terminated C string from the binary file at the current file position, returns a single C string'''
cstr = ''
byte = self.get_uint8()
while byte != 0:
cstr += "%c" % byte
byte = self.get_uint8()
return cstr
def get_n_sint8(self, n, fail_value=0):
'''Extract "n" int8_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'b', s)
else:
return (fail_value,) * n
def get_n_uint8(self, n, fail_value=0):
'''Extract "n" uint8_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'B', s)
else:
return (fail_value,) * n
def get_n_sint16(self, n, fail_value=0):
'''Extract "n" int16_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(2 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'h', s)
else:
return (fail_value,) * n
def get_n_uint16(self, n, fail_value=0):
'''Extract "n" uint16_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(2 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'H', s)
else:
return (fail_value,) * n
def get_n_sint32(self, n, fail_value=0):
'''Extract "n" int32_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(4 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'i', s)
else:
return (fail_value,) * n
def get_n_uint32(self, n, fail_value=0):
'''Extract "n" uint32_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(4 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'I', s)
else:
return (fail_value,) * n
def get_n_sint64(self, n, fail_value=0):
'''Extract "n" int64_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(8 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'q', s)
else:
return (fail_value,) * n
def get_n_uint64(self, n, fail_value=0):
'''Extract "n" uint64_t integers from the binary file at the current file position, returns a list of integers'''
s = self.read_size(8 * n)
if s:
return struct.unpack(self.byte_order + ("%u" % n) + 'Q', s)
else:
return (fail_value,) * n
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