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# $Id: gzip.py 23 2006-11-08 15:45:33Z dugsong $
# -*- coding: utf-8 -*-
"""GNU zip."""
from __future__ import print_function
from __future__ import absolute_import
import struct
import zlib
import binascii
from . import dpkt
# RFC 1952
GZIP_MAGIC = b'\x1f\x8b'
# Compression methods
GZIP_MSTORED = 0
GZIP_MCOMPRESS = 1
GZIP_MPACKED = 2
GZIP_MLZHED = 3
GZIP_MDEFLATE = 8
# Flags
GZIP_FTEXT = 0x01
GZIP_FHCRC = 0x02
GZIP_FEXTRA = 0x04
GZIP_FNAME = 0x08
GZIP_FCOMMENT = 0x10
GZIP_FENCRYPT = 0x20
GZIP_FRESERVED = 0xC0
# OS
GZIP_OS_MSDOS = 0
GZIP_OS_AMIGA = 1
GZIP_OS_VMS = 2
GZIP_OS_UNIX = 3
GZIP_OS_VMCMS = 4
GZIP_OS_ATARI = 5
GZIP_OS_OS2 = 6
GZIP_OS_MACOS = 7
GZIP_OS_ZSYSTEM = 8
GZIP_OS_CPM = 9
GZIP_OS_TOPS20 = 10
GZIP_OS_WIN32 = 11
GZIP_OS_QDOS = 12
GZIP_OS_RISCOS = 13
GZIP_OS_UNKNOWN = 255
GZIP_FENCRYPT_LEN = 12
class GzipExtra(dpkt.Packet):
__byte_order__ = '<'
__hdr__ = (
('id', '2s', ''),
('len', 'H', 0)
)
class Gzip(dpkt.Packet):
__byte_order__ = '<'
__hdr__ = (
('magic', '2s', GZIP_MAGIC),
('method', 'B', GZIP_MDEFLATE),
('flags', 'B', 0),
('mtime', 'I', 0),
('xflags', 'B', 0),
('os', 'B', GZIP_OS_UNIX),
('extra', '0s', ''), # XXX - GZIP_FEXTRA
('filename', '0s', ''), # XXX - GZIP_FNAME
('comment', '0s', '') # XXX - GZIP_FCOMMENT
)
def unpack(self, buf):
super(Gzip, self).unpack(buf)
if self.flags & GZIP_FEXTRA:
if len(self.data) < 2:
raise dpkt.NeedData('Gzip extra')
n = struct.unpack('<H', self.data[:2])[0]
if len(self.data) < 2 + n:
raise dpkt.NeedData('Gzip extra')
self.extra = GzipExtra(self.data[2:2 + n])
self.data = self.data[2 + n:]
if self.flags & GZIP_FNAME:
n = self.data.find(b'\x00')
if n == -1:
raise dpkt.NeedData('Gzip end of file name not found')
self.filename = self.data[:n].decode('utf-8')
self.data = self.data[n + 1:]
if self.flags & GZIP_FCOMMENT:
n = self.data.find(b'\x00')
if n == -1:
raise dpkt.NeedData('Gzip end of comment not found')
self.comment = self.data[:n]
self.data = self.data[n + 1:]
if self.flags & GZIP_FENCRYPT:
if len(self.data) < GZIP_FENCRYPT_LEN:
raise dpkt.NeedData('Gzip encrypt')
self.data = self.data[GZIP_FENCRYPT_LEN:] # XXX - skip
if self.flags & GZIP_FHCRC:
if len(self.data) < 2:
raise dpkt.NeedData('Gzip hcrc')
self.data = self.data[2:] # XXX - skip
def pack_hdr(self):
l = []
if self.extra:
self.flags |= GZIP_FEXTRA
s = bytes(self.extra)
l.append(struct.pack('<H', len(s)))
l.append(s)
if self.filename:
self.flags |= GZIP_FNAME
l.append(self.filename)
l.append(b'\x00')
if self.comment:
self.flags |= GZIP_FCOMMENT
l.append(self.comment)
l.append(b'\x00')
l.insert(0, super(Gzip, self).pack_hdr())
return b''.join(l)
def compress(self):
"""Compress self.data."""
c = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS,
zlib.DEF_MEM_LEVEL, 0)
self.data = c.compress(self.data)
def decompress(self):
"""Return decompressed payload."""
d = zlib.decompressobj(-zlib.MAX_WBITS)
return d.decompress(self.data)
_hexdecode = binascii.a2b_hex
class TestGzip(object):
"""This data is created with the gzip command line tool"""
@classmethod
def setup_class(cls):
cls.data = _hexdecode(b'1F8B' # magic
b'080880C185560003' # header
b'68656C6C6F2E74787400' # filename
b'F348CDC9C95728CF2FCA4951E40200' # data
b'41E4A9B20D000000') # checksum
cls.p = Gzip(cls.data)
def test_method(self):
assert (self.p.method == GZIP_MDEFLATE)
def test_flags(self):
assert (self.p.flags == GZIP_FNAME)
def test_mtime(self):
# Fri Jan 01 00:00:00 2016 UTC
assert (self.p.mtime == 0x5685c180)
def test_xflags(self):
assert (self.p.xflags == 0)
def test_os(self):
assert (self.p.os == GZIP_OS_UNIX)
def test_filename(self):
assert (self.p.filename == "hello.txt") # always str (utf-8)
def test_decompress(self):
assert (self.p.decompress() == b"Hello world!\n") # always bytes
if __name__ == '__main__':
import sys
gz = Gzip(open(sys.argv[1]).read())
print(repr(gz), repr(gz.decompress()))
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