"""Functions that read and write gzipped files.

The user of the file doesn't have to worry about the compression,

but random access is not allowed."""

# based on Andrew Kuchling's minigzip.py distributed with the zlib module

import struct, sys, time

import zlib

import builtins

__all__ = ["GzipFile","open"]

FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16

READ, WRITE = 1, 2

def U32(i):

"""Return i as an unsigned integer, assuming it fits in 32 bits.

If it's >= 2GB when viewed as a 32-bit unsigned int, return a long.

"""

if i < 0:

i += 1 << 32

return i

def LOWU32(i):

"""Return the low-order 32 bits, as a non-negative int"""

return i & 0xFFFFFFFF

def write32u(output, value):

# The L format writes the bit pattern correctly whether signed

# or unsigned.

output.write(struct.pack("<L", value))

def read32(input):

return struct.unpack("<I", input.read(4))[0]

def open(filename, mode="rb", compresslevel=9):

"""Shorthand for GzipFile(filename, mode, compresslevel).

The filename argument is required; mode defaults to 'rb'

and compresslevel defaults to 9.

"""

return GzipFile(filename, mode, compresslevel)

class GzipFile:

"""The GzipFile class simulates most of the methods of a file object with

the exception of the readinto() and truncate() methods.

"""

myfileobj = None

max_read_chunk = 10 * 1024 * 1024 # 10Mb

def __init__(self, filename=None, mode=None,

compresslevel=9, fileobj=None):

"""Constructor for the GzipFile class.

At least one of fileobj and filename must be given a

non-trivial value.

The new class instance is based on fileobj, which can be a regular

file, a StringIO object, or any other object which simulates a file.

It defaults to None, in which case filename is opened to provide

a file object.

When fileobj is not None, the filename argument is only used to be

included in the gzip file header, which may includes the original

filename of the uncompressed file. It defaults to the filename of

fileobj, if discernible; otherwise, it defaults to the empty string,

and in this case the original filename is not included in the header.

The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', or 'wb',

depending on whether the file will be read or written. The default

is the mode of fileobj if discernible; otherwise, the default is 'rb'.

Be aware that only the 'rb', 'ab', and 'wb' values should be used

for cross-platform portability.

The compresslevel argument is an integer from 1 to 9 controlling the

level of compression; 1 is fastest and produces the least compression,

and 9 is slowest and produces the most compression. The default is 9.

"""

# guarantee the file is opened in binary mode on platforms

# that care about that sort of thing

if mode and 'b' not in mode:

mode += 'b'

if fileobj is None:

fileobj = self.myfileobj = builtins.open(filename, mode or 'rb')

if filename is None:

if hasattr(fileobj, 'name'): filename = fileobj.name

else: filename = ''

if mode is None:

if hasattr(fileobj, 'mode'): mode = fileobj.mode

else: mode = 'rb'

if mode[0:1] == 'r':

self.mode = READ

# Set flag indicating start of a new member

self._new_member = True

self.extrabuf = b""

self.extrasize = 0

self.name = filename

# Starts small, scales exponentially

self.min_readsize = 100

elif mode[0:1] == 'w' or mode[0:1] == 'a':

self.mode = WRITE

self._init_write(filename)

self.compress = zlib.compressobj(compresslevel,

zlib.DEFLATED,

-zlib.MAX_WBITS,

zlib.DEF_MEM_LEVEL,

0)

else:

raise IOError("Mode " + mode + " not supported")

self.fileobj = fileobj

self.offset = 0

if self.mode == WRITE:

self._write_gzip_header()

@property

def filename(self):

import warnings

warnings.warn("use the name attribute", DeprecationWarning)

if self.mode == WRITE and self.name[-3:] != ".gz":

return self.name + ".gz"

return self.name

def __repr__(self):

s = repr(self.fileobj)

return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'

def _init_write(self, filename):

self.name = filename

self.crc = zlib.crc32("") & 0xffffffff

self.size = 0

self.writebuf = []

self.bufsize = 0

def _write_gzip_header(self):

self.fileobj.write(b'\037\213') # magic header

self.fileobj.write(b'\010') # compression method

try:

# RFC 1952 requires the FNAME field to be Latin-1. Do not

# include filenames that cannot be represented that way.

fname = self.name.encode('latin-1')

if fname.endswith(b'.gz'):

fname = fname[:-3]

except UnicodeEncodeError:

fname = b''

flags = 0

if fname:

flags = FNAME

self.fileobj.write(chr(flags).encode('latin-1'))

write32u(self.fileobj, int(time.time()))

self.fileobj.write(b'\002')

self.fileobj.write(b'\377')

if fname:

self.fileobj.write(fname + b'\000')

def _init_read(self):

self.crc = zlib.crc32("") & 0xffffffff

self.size = 0

def _read_gzip_header(self):

magic = self.fileobj.read(2)

if magic != b'\037\213':

raise IOError('Not a gzipped file')

method = ord( self.fileobj.read(1) )

if method != 8:

raise IOError('Unknown compression method')

flag = ord( self.fileobj.read(1) )

# modtime = self.fileobj.read(4)

# extraflag = self.fileobj.read(1)

# os = self.fileobj.read(1)

self.fileobj.read(6)

if flag & FEXTRA:

# Read & discard the extra field, if present

xlen = ord(self.fileobj.read(1))

xlen = xlen + 256*ord(self.fileobj.read(1))

self.fileobj.read(xlen)

if flag & FNAME:

# Read and discard a null-terminated string containing the filename

while True:

s = self.fileobj.read(1)

if not s or s==b'\000':

break

if flag & FCOMMENT:

# Read and discard a null-terminated string containing a comment

while True:

s = self.fileobj.read(1)

if not s or s==b'\000':

break

if flag & FHCRC:

self.fileobj.read(2) # Read & discard the 16-bit header CRC

def write(self,data):

if self.mode != WRITE:

import errno

raise IOError(errno.EBADF, "write() on read-only GzipFile object")

if self.fileobj is None:

raise ValueError("write() on closed GzipFile object")

if len(data) > 0:

self.size = self.size + len(data)

self.crc = zlib.crc32(data, self.crc) & 0xffffffff

self.fileobj.write( self.compress.compress(data) )

self.offset += len(data)

def read(self, size=-1):

if self.mode != READ:

import errno

raise IOError(errno.EBADF, "read() on write-only GzipFile object")

if self.extrasize <= 0 and self.fileobj is None:

return b''

readsize = 1024

if size < 0: # get the whole thing

try:

while True:

self._read(readsize)

readsize = min(self.max_read_chunk, readsize * 2)

except EOFError:

size = self.extrasize

else: # just get some more of it

try:

while size > self.extrasize:

self._read(readsize)

readsize = min(self.max_read_chunk, readsize * 2)

except EOFError:

if size > self.extrasize:

size = self.extrasize

chunk = self.extrabuf[:size]

self.extrabuf = self.extrabuf[size:]

self.extrasize = self.extrasize - size

self.offset += size

return chunk

def _unread(self, buf):

self.extrabuf = buf + self.extrabuf

self.extrasize = len(buf) + self.extrasize

self.offset -= len(buf)

def _read(self, size=1024):

if self.fileobj is None:

raise EOFError("Reached EOF")

if self._new_member:

# If the _new_member flag is set, we have to

# jump to the next member, if there is one.

#

# First, check if we're at the end of the file;

# if so, it's time to stop; no more members to read.

pos = self.fileobj.tell() # Save current position

self.fileobj.seek(0, 2) # Seek to end of file

if pos == self.fileobj.tell():

raise EOFError("Reached EOF")

else:

self.fileobj.seek( pos ) # Return to original position

self._init_read()

self._read_gzip_header()

self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)

self._new_member = False

# Read a chunk of data from the file

buf = self.fileobj.read(size)

# If the EOF has been reached, flush the decompression object

# and mark this object as finished.

if buf == b"":

uncompress = self.decompress.flush()

self._read_eof()

self._add_read_data( uncompress )

raise EOFError('Reached EOF')

uncompress = self.decompress.decompress(buf)

self._add_read_data( uncompress )

if self.decompress.unused_data != b"":

# Ending case: we've come to the end of a member in the file,

# so seek back to the start of the unused data, finish up

# this member, and read a new gzip header.

# (The number of bytes to seek back is the length of the unused

# data, minus 8 because _read_eof() will rewind a further 8 bytes)

self.fileobj.seek( -len(self.decompress.unused_data)+8, 1)

# Check the CRC and file size, and set the flag so we read

# a new member on the next call

self._read_eof()

self._new_member = True

def _add_read_data(self, data):

self.crc = zlib.crc32(data, self.crc) & 0xffffffff

self.extrabuf = self.extrabuf + data

self.extrasize = self.extrasize + len(data)

self.size = self.size + len(data)

def _read_eof(self):

# We've read to the end of the file, so we have to rewind in order

# to reread the 8 bytes containing the CRC and the file size.

# We check the that the computed CRC and size of the

# uncompressed data matches the stored values. Note that the size

# stored is the true file size mod 2**32.

self.fileobj.seek(-8, 1)

crc32 = read32(self.fileobj)

isize = read32(self.fileobj) # may exceed 2GB

if crc32 != self.crc:

raise IOError("CRC check failed %s != %s" % (hex(crc32),

hex(self.crc)))

elif isize != (self.size & 0xffffffff):

raise IOError("Incorrect length of data produced")

def close(self):

if self.fileobj is None:

return

if self.mode == WRITE:

self.fileobj.write(self.compress.flush())

write32u(self.fileobj, self.crc)

# self.size may exceed 2GB, or even 4GB

write32u(self.fileobj, self.size & 0xffffffff)

self.fileobj = None

elif self.mode == READ:

self.fileobj = None

if self.myfileobj:

self.myfileobj.close()

self.myfileobj = None

def __del__(self):

try:

if (self.myfileobj is None and

self.fileobj is None):

return

except AttributeError:

return

self.close()

def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):

if self.mode == WRITE:

# Ensure the compressor's buffer is flushed

self.fileobj.write(self.compress.flush(zlib_mode))

self.fileobj.flush()

def fileno(self):

"""Invoke the underlying file object's fileno() method.

This will raise AttributeError if the underlying file object

doesn't support fileno().

"""

return self.fileobj.fileno()

def isatty(self):

return False

def tell(self):

return self.offset

def rewind(self):

'''Return the uncompressed stream file position indicator to the

beginning of the file'''

if self.mode != READ:

raise IOError("Can't rewind in write mode")

self.fileobj.seek(0)

self._new_member = True

self.extrabuf = b""

self.extrasize = 0

self.offset = 0

def seek(self, offset, whence=0):

if whence:

if whence == 1:

offset = self.offset + offset

else:

raise ValueError('Seek from end not supported')

if self.mode == WRITE:

if offset < self.offset:

raise IOError('Negative seek in write mode')

count = offset - self.offset

chunk = bytes(1024)

for i in range(count // 1024):

self.write(chunk)

self.write(bytes(count % 1024))

elif self.mode == READ:

if offset < self.offset:

# for negative seek, rewind and do positive seek

self.rewind()

count = offset - self.offset

for i in range(count // 1024):

self.read(1024)

self.read(count % 1024)

def readline(self, size=-1):

if size < 0:

size = sys.maxsize

readsize = self.min_readsize

else:

readsize = size

bufs = []

while size != 0:

c = self.read(readsize)

i = c.find(b'\n')

# We set i=size to break out of the loop under two

# conditions: 1) there's no newline, and the chunk is

# larger than size, or 2) there is a newline, but the

# resulting line would be longer than 'size'.

if (size <= i) or (i == -1 and len(c) > size):

i = size - 1

if i >= 0 or c == b'':

bufs.append(c[:i + 1]) # Add portion of last chunk

self._unread(c[i + 1:]) # Push back rest of chunk

break

# Append chunk to list, decrease 'size',

bufs.append(c)

size = size - len(c)

readsize = min(size, readsize * 2)

if readsize > self.min_readsize:

self.min_readsize = min(readsize, self.min_readsize * 2, 512)

return b''.join(bufs) # Return resulting line

def readlines(self, sizehint=0):

# Negative numbers result in reading all the lines

if sizehint <= 0:

sizehint = sys.maxsize

L = []

while sizehint > 0:

line = self.readline()

if line == b"":

break

L.append(line)

sizehint = sizehint - len(line)

return L

def writelines(self, L):

for line in L:

self.write(line)

def __iter__(self):

return self

def __next__(self):

line = self.readline()

if line:

return line

else:

raise StopIteration

def _test():

# Act like gzip; with -d, act like gunzip.

# The input file is not deleted, however, nor are any other gzip

# options or features supported.

args = sys.argv[1:]

decompress = args and args[0] == "-d"

if decompress:

args = args[1:]

if not args:

args = ["-"]

for arg in args:

if decompress:

if arg == "-":

f = GzipFile(filename="", mode="rb", fileobj=sys.stdin)

g = sys.stdout

else:

if arg[-3:] != ".gz":

print("filename doesn't end in .gz:", repr(arg))

continue

f = open(arg, "rb")

g = builtins.open(arg[:-3], "wb")

else:

if arg == "-":

f = sys.stdin

g = GzipFile(filename="", mode="wb", fileobj=sys.stdout)

else:

f = builtins.open(arg, "rb")

g = open(arg + ".gz", "wb")

while True:

chunk = f.read(1024)

if not chunk:

break

g.write(chunk)

if g is not sys.stdout:

g.close()

if f is not sys.stdin:

f.close()

if __name__ == '__main__':

_test()