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"""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, os 

import zlib 

import builtins 

import io 

import _compression 

 

__all__ = ["GzipFile", "open", "compress", "decompress"] 

 

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

 

READ, WRITE = 1, 2 

 

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

encoding=None, errors=None, newline=None): 

"""Open a gzip-compressed file in binary or text mode. 

 

The filename argument can be an actual filename (a str or bytes object), or 

an existing file object to read from or write to. 

 

The mode argument can be "r", "rb", "w", "wb", "x", "xb", "a" or "ab" for 

binary mode, or "rt", "wt", "xt" or "at" for text mode. The default mode is 

"rb", and the default compresslevel is 9. 

 

For binary mode, this function is equivalent to the GzipFile constructor: 

GzipFile(filename, mode, compresslevel). In this case, the encoding, errors 

and newline arguments must not be provided. 

 

For text mode, a GzipFile object is created, and wrapped in an 

io.TextIOWrapper instance with the specified encoding, error handling 

behavior, and line ending(s). 

 

""" 

if "t" in mode: 

if "b" in mode: 

raise ValueError("Invalid mode: %r" % (mode,)) 

else: 

if encoding is not None: 

raise ValueError("Argument 'encoding' not supported in binary mode") 

if errors is not None: 

raise ValueError("Argument 'errors' not supported in binary mode") 

if newline is not None: 

raise ValueError("Argument 'newline' not supported in binary mode") 

 

gz_mode = mode.replace("t", "") 

if isinstance(filename, (str, bytes, os.PathLike)): 

binary_file = GzipFile(filename, gz_mode, compresslevel) 

elif hasattr(filename, "read") or hasattr(filename, "write"): 

binary_file = GzipFile(None, gz_mode, compresslevel, filename) 

else: 

raise TypeError("filename must be a str or bytes object, or a file") 

 

if "t" in mode: 

return io.TextIOWrapper(binary_file, encoding, errors, newline) 

else: 

return binary_file 

 

def write32u(output, value): 

# The L format writes the bit pattern correctly whether signed 

# or unsigned. 

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

 

class _PaddedFile: 

"""Minimal read-only file object that prepends a string to the contents 

of an actual file. Shouldn't be used outside of gzip.py, as it lacks 

essential functionality.""" 

 

def __init__(self, f, prepend=b''): 

self._buffer = prepend 

self._length = len(prepend) 

self.file = f 

self._read = 0 

 

def read(self, size): 

if self._read is None: 

return self.file.read(size) 

if self._read + size <= self._length: 

read = self._read 

self._read += size 

return self._buffer[read:self._read] 

else: 

read = self._read 

self._read = None 

return self._buffer[read:] + \ 

self.file.read(size-self._length+read) 

 

def prepend(self, prepend=b''): 

if self._read is None: 

self._buffer = prepend 

else: # Assume data was read since the last prepend() call 

self._read -= len(prepend) 

return 

self._length = len(self._buffer) 

self._read = 0 

 

def seek(self, off): 

self._read = None 

self._buffer = None 

return self.file.seek(off) 

 

def seekable(self): 

return True # Allows fast-forwarding even in unseekable streams 

 

class GzipFile(_compression.BaseStream): 

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

the exception of the truncate() method. 

 

This class only supports opening files in binary mode. If you need to open a 

compressed file in text mode, use the gzip.open() function. 

 

""" 

 

# Overridden with internal file object to be closed, if only a filename 

# is passed in 

myfileobj = None 

 

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

compresslevel=9, fileobj=None, mtime=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, an io.BytesIO 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 include 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', 'wb', 'x', or 

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

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

A mode of 'r' is equivalent to one of 'rb', and similarly for 'w' and 

'wb', 'a' and 'ab', and 'x' and 'xb'. 

 

The compresslevel argument is an integer from 0 to 9 controlling the 

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

and 9 is slowest and produces the most compression. 0 is no compression 

at all. The default is 9. 

 

The mtime argument is an optional numeric timestamp to be written 

to the last modification time field in the stream when compressing. 

If omitted or None, the current time is used. 

 

""" 

 

if mode and ('t' in mode or 'U' in mode): 

raise ValueError("Invalid mode: {!r}".format(mode)) 

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: 

filename = getattr(fileobj, 'name', '') 

if not isinstance(filename, (str, bytes)): 

filename = '' 

else: 

filename = os.fspath(filename) 

if mode is None: 

mode = getattr(fileobj, 'mode', 'rb') 

 

if mode.startswith('r'): 

self.mode = READ 

raw = _GzipReader(fileobj) 

self._buffer = io.BufferedReader(raw) 

self.name = filename 

 

elif mode.startswith(('w', 'a', 'x')): 

self.mode = WRITE 

self._init_write(filename) 

self.compress = zlib.compressobj(compresslevel, 

zlib.DEFLATED, 

-zlib.MAX_WBITS, 

zlib.DEF_MEM_LEVEL, 

0) 

self._write_mtime = mtime 

else: 

raise ValueError("Invalid mode: {!r}".format(mode)) 

 

self.fileobj = fileobj 

 

if self.mode == WRITE: 

self._write_gzip_header() 

 

@property 

def filename(self): 

import warnings 

warnings.warn("use the name attribute", DeprecationWarning, 2) 

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

return self.name + ".gz" 

return self.name 

 

@property 

def mtime(self): 

"""Last modification time read from stream, or None""" 

return self._buffer.raw._last_mtime 

 

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(b"") 

self.size = 0 

self.writebuf = [] 

self.bufsize = 0 

self.offset = 0 # Current file offset for seek(), tell(), etc 

 

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 = os.path.basename(self.name) 

if not isinstance(fname, bytes): 

fname = fname.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')) 

mtime = self._write_mtime 

if mtime is None: 

mtime = time.time() 

write32u(self.fileobj, int(mtime)) 

self.fileobj.write(b'\002') 

self.fileobj.write(b'\377') 

if fname: 

self.fileobj.write(fname + b'\000') 

 

def write(self,data): 

self._check_not_closed() 

if self.mode != WRITE: 

import errno 

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

 

if self.fileobj is None: 

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

 

if isinstance(data, bytes): 

length = len(data) 

else: 

# accept any data that supports the buffer protocol 

data = memoryview(data) 

length = data.nbytes 

 

if length > 0: 

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

self.size += length 

self.crc = zlib.crc32(data, self.crc) 

self.offset += length 

 

return length 

 

def read(self, size=-1): 

self._check_not_closed() 

if self.mode != READ: 

import errno 

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

return self._buffer.read(size) 

 

def read1(self, size=-1): 

"""Implements BufferedIOBase.read1() 

 

Reads up to a buffer's worth of data is size is negative.""" 

self._check_not_closed() 

if self.mode != READ: 

import errno 

raise OSError(errno.EBADF, "read1() on write-only GzipFile object") 

 

if size < 0: 

size = io.DEFAULT_BUFFER_SIZE 

return self._buffer.read1(size) 

 

def peek(self, n): 

self._check_not_closed() 

if self.mode != READ: 

import errno 

raise OSError(errno.EBADF, "peek() on write-only GzipFile object") 

return self._buffer.peek(n) 

 

@property 

def closed(self): 

return self.fileobj is None 

 

def close(self): 

fileobj = self.fileobj 

if fileobj is None: 

return 

self.fileobj = None 

try: 

if self.mode == WRITE: 

fileobj.write(self.compress.flush()) 

write32u(fileobj, self.crc) 

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

write32u(fileobj, self.size & 0xffffffff) 

elif self.mode == READ: 

self._buffer.close() 

finally: 

myfileobj = self.myfileobj 

if myfileobj: 

self.myfileobj = None 

myfileobj.close() 

 

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

self._check_not_closed() 

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 rewind(self): 

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

beginning of the file''' 

if self.mode != READ: 

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

self._buffer.seek(0) 

 

def readable(self): 

return self.mode == READ 

 

def writable(self): 

return self.mode == WRITE 

 

def seekable(self): 

return True 

 

def seek(self, offset, whence=io.SEEK_SET): 

if self.mode == WRITE: 

if whence != io.SEEK_SET: 

if whence == io.SEEK_CUR: 

offset = self.offset + offset 

else: 

raise ValueError('Seek from end not supported') 

if offset < self.offset: 

raise OSError('Negative seek in write mode') 

count = offset - self.offset 

chunk = b'\0' * 1024 

for i in range(count // 1024): 

self.write(chunk) 

self.write(b'\0' * (count % 1024)) 

elif self.mode == READ: 

self._check_not_closed() 

return self._buffer.seek(offset, whence) 

 

return self.offset 

 

def readline(self, size=-1): 

self._check_not_closed() 

return self._buffer.readline(size) 

 

 

class _GzipReader(_compression.DecompressReader): 

def __init__(self, fp): 

super().__init__(_PaddedFile(fp), zlib.decompressobj, 

wbits=-zlib.MAX_WBITS) 

# Set flag indicating start of a new member 

self._new_member = True 

self._last_mtime = None 

 

def _init_read(self): 

self._crc = zlib.crc32(b"") 

self._stream_size = 0 # Decompressed size of unconcatenated stream 

 

def _read_exact(self, n): 

'''Read exactly *n* bytes from `self._fp` 

 

This method is required because self._fp may be unbuffered, 

i.e. return short reads. 

''' 

 

data = self._fp.read(n) 

while len(data) < n: 

b = self._fp.read(n - len(data)) 

if not b: 

raise EOFError("Compressed file ended before the " 

"end-of-stream marker was reached") 

data += b 

return data 

 

def _read_gzip_header(self): 

magic = self._fp.read(2) 

if magic == b'': 

return False 

 

if magic != b'\037\213': 

raise OSError('Not a gzipped file (%r)' % magic) 

 

(method, flag, 

self._last_mtime) = struct.unpack("<BBIxx", self._read_exact(8)) 

if method != 8: 

raise OSError('Unknown compression method') 

 

if flag & FEXTRA: 

# Read & discard the extra field, if present 

extra_len, = struct.unpack("<H", self._read_exact(2)) 

self._read_exact(extra_len) 

if flag & FNAME: 

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

while True: 

s = self._fp.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._fp.read(1) 

if not s or s==b'\000': 

break 

if flag & FHCRC: 

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

return True 

 

def read(self, size=-1): 

if size < 0: 

return self.readall() 

# size=0 is special because decompress(max_length=0) is not supported 

if not size: 

return b"" 

 

# For certain input data, a single 

# call to decompress() may not return 

# any data. In this case, retry until we get some data or reach EOF. 

while True: 

if self._decompressor.eof: 

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

# so finish up this member, and read a new gzip header. 

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

# a new member 

self._read_eof() 

self._new_member = True 

self._decompressor = self._decomp_factory( 

**self._decomp_args) 

 

if self._new_member: 

# If the _new_member flag is set, we have to 

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

self._init_read() 

if not self._read_gzip_header(): 

self._size = self._pos 

return b"" 

self._new_member = False 

 

# Read a chunk of data from the file 

buf = self._fp.read(io.DEFAULT_BUFFER_SIZE) 

 

uncompress = self._decompressor.decompress(buf, size) 

if self._decompressor.unconsumed_tail != b"": 

self._fp.prepend(self._decompressor.unconsumed_tail) 

elif self._decompressor.unused_data != b"": 

# Prepend the already read bytes to the fileobj so they can 

# be seen by _read_eof() and _read_gzip_header() 

self._fp.prepend(self._decompressor.unused_data) 

 

if uncompress != b"": 

break 

if buf == b"": 

raise EOFError("Compressed file ended before the " 

"end-of-stream marker was reached") 

 

self._add_read_data( uncompress ) 

self._pos += len(uncompress) 

return uncompress 

 

def _add_read_data(self, data): 

self._crc = zlib.crc32(data, self._crc) 

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

 

def _read_eof(self): 

# We've read to the end of the file 

# 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. 

crc32, isize = struct.unpack("<II", self._read_exact(8)) 

if crc32 != self._crc: 

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

hex(self._crc))) 

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

raise OSError("Incorrect length of data produced") 

 

# Gzip files can be padded with zeroes and still have archives. 

# Consume all zero bytes and set the file position to the first 

# non-zero byte. See http://www.gzip.org/#faq8 

c = b"\x00" 

while c == b"\x00": 

c = self._fp.read(1) 

if c: 

self._fp.prepend(c) 

 

def _rewind(self): 

super()._rewind() 

self._new_member = True 

 

def compress(data, compresslevel=9): 

"""Compress data in one shot and return the compressed string. 

Optional argument is the compression level, in range of 0-9. 

""" 

buf = io.BytesIO() 

with GzipFile(fileobj=buf, mode='wb', compresslevel=compresslevel) as f: 

f.write(data) 

return buf.getvalue() 

 

def decompress(data): 

"""Decompress a gzip compressed string in one shot. 

Return the decompressed string. 

""" 

with GzipFile(fileobj=io.BytesIO(data)) as f: 

return f.read() 

 

 

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.buffer) 

g = sys.stdout.buffer 

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.buffer 

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

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.buffer: 

g.close() 

if f is not sys.stdin.buffer: 

f.close() 

 

if __name__ == '__main__': 

_test()