Add office document formats

[magbyr]

Adds formats:

• doc - application/msword
• docx - application/vnd.openxmlformats-officedocument.wordprocessingml.document
• odt - application/vnd.oasis.opendocument.text
• xls - application/vnd.ms-excel
• xlsx - application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
• ods - application/vnd.oasis.opendocument.spreadsheet
• ppt - application/vnd.ms-powerpoint
• pptx - application/vnd.openxmlformats-officedocument.presentationml.presentation
• odp - application/vnd.oasis.opendocument.presentation

[magbyr]

Hope these changes can be useful for the project. We're relying on filetype.py usage in our startup, so we're committed to keeping these formats/signatures updated if needed. Copied some signatures / code from the go version, but added some changes because of differences in the files produced by LibreOffice.

[babenek]

Optimization suggestions.
UnitTests: complex return (...) cannot produce code coverage for analysis. May be if-else does not overhead...

[babenek]

Suggested change

	len(buf) > 7
	and buf[0:8] == b"\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1"
	and (
	(len(buf) > 515 and buf[512:515] == b"\xEC\xA5\xC1\x00") # MS Office
	or (
	len(buf) > 2142
	and b"\x00\x0A\x00\x00\x00MSWordDoc\x00\x10\x00\x00\x00Word.Document.8\x00\xF49\xB2q"
	in buf[2075:2142]
	) # LibreOffice
	)
	)
	len(buf) > 515
	and buf[0:8] == b"\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1"
	and (
	buf[512:515] == b"\xEC\xA5\xC1\x00" # MS Office
	or (
	len(buf) > 2142
	and b"\x00\x0A\x00\x00\x00MSWordDoc\x00\x10\x00\x00\x00Word.Document.8\x00\xF49\xB2q"
	in buf[2075:2142]
	) # LibreOffice
	)
	)

simple optimization.

[magbyr]

I have changed the match methods a bit. Probably better for coverage calculation - but slightly slower. What do you think?

[babenek]

Probably it is so due you used additional assignments.
I draft my suggestion. Anyway if it so slowly - rollback the changes.
Additionally you can test with #132 - sometimes it found uncaught exceptions. But you have to change -max_len=262 to 8K.

[magbyr]

Cool. I did the changes and tested with atheris. Found no errors in new code. Atheris found an error in the isobmff class regarding unicode decoding. I think a simple "errors=ignore" on the decode method could be a solution there...

Anyway. Hopefully the latest changes works better with coverage calculation?

[babenek]

Cool, then may be the PR will me merged. Yes, the fix works #131 .

[babenek]

Suggested change

	header_match = (
	len(buf) > 8 and buf[0:8] == b"\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1"
	)
	subheader_match = (
	header_match
	and len(buf) > 520
	and (
	(
	buf[512:516] == b"\xFD\xFF\xFF\xFF"
	and (buf[518] == 0x00 or buf[518] == 0x02)
	)
	or (buf[512:520] == b"\x09\x08\x10\x00\x00\x06\x05\x00")
	or (
	len(buf) > 2095
	and b"\xE2\x00\x00\x00\x5C\x00\x70\x00\x04\x00\x00Calc"
	in buf[1568:2095]
	)
	)
	)
	return header_match and subheader_match
	if len(buf) > 520 and buf[0:8] == b"\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1":
	if buf[512:516] == b"\xFD\xFF\xFF\xFF" and (buf[518] == 0x00 or buf[518] == 0x02) \
	or buf[512:520] == b"\x09\x08\x10\x00\x00\x06\x05\x00":
	return True
	elif len(buf) > 2095:
	return b"\xE2\x00\x00\x00\x5C\x00\x70\x00\x04\x00\x00Calc" in buf[1568:2095]
	return False

Please, check my suggestion. May be spaces missed/extra.