class FileAnalyzer():
'''
Analizes files according to dictionaries
'''
def __init__(self, filename, chunksize=4 * utils.MB):
'''
Initiates a file analyzer
\nArgs:
\n\t filename (str): the filename to analize
\n\t chunksize (int): the size of chunks to be read at a time from the file
\t(default is 4,194,304 byts (4MB))
'''
self.filename = filename
self.res = Result(f"{filename}_patterns.json")
self.chunksize = chunksize
self.match_ranges = {}
def find_patterns(self, dic, upto_offset=0, repeating=0) -> None:
'''
Find the patterns from the dictionary in the file upto the offset given, add them to the result
\nArgs:
\n\tdic (dict): The pattern dictionary
\n\t`upto_offset` (int): the offset of the last byte to be read
\t (default is 0(read the whole file))
\n\t repeating (int): the shortest repeated byte sequance to write down
\t (default is 0(don't search for repeated bytes))
'''
buff = Buffer(self.chunksize * 2) # 2 chunks per buffer
# in case of a match seperating between two chunks
if repeating:
repet_ex = re.compile(r"(..)\1{" + str(repeating) + ",}")
# re searches faster for pre compiled expresions
regex = {re.compile(key): val for key, val in dic.items()}
for i, chunk in enumerate(utils.file_to_chunks_generator(self.filename, chunksize=self.chunksize, upto_offset=upto_offset)):
buff.update(chunk)
new_ranges = buff.pattern_ranges_in_buffer(dic)
self.update_ranges(new_ranges, i)
if repeating:
for match in re.finditer(repet_ex, "".join(chunk)):
self.res.add("reapiting byte", i+match.start()//2, match.end()//2-match.start()//2,
repeater=utils.format_byte(hex(int(match.groups()[0]))))
self.res.add_from_dict(self.match_ranges)
def write_results(self) -> None:
self.res.write_to_file()
def update_ranges(self, new_ranges, current_chunk_index) -> None:
''''
updates the current ranges according to the new ranges
\nArgs:
\n\t `new_ranges` (dict): a dictionary from the
\t name to a dictionary of the spans of the matches
\n\t current_chunk_index (int)
'''
for name, rng_list in new_ranges.items():
for rng in rng_list:
start = rng["start"] + \
(current_chunk_index-3) * self.chunksize//2
length = (rng["end"] - rng["start"])
if name not in self.match_ranges:
self.match_ranges[name] = {}
if start in self.match_ranges[name]:
length = max(length, self.match_ranges[name][start])
self.match_ranges[name][start] = length
