"""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__ = ["BadGzipFile", "GzipFile", "open", "compress", "decompress"]

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

READ, WRITE = 1, 2

_COMPRESS_LEVEL_FAST = 1
_COMPRESS_LEVEL_TRADEOFF = 6
_COMPRESS_LEVEL_BEST = 9


def open(filename, mode="rb", compresslevel=_COMPRESS_LEVEL_BEST,
 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 BadGzipFile(OSError):
 """Exception raised in some cases for invalid gzip files."""


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=_COMPRESS_LEVEL_BEST, 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円213円') # magic header
 self.fileobj.write(b'010円') # 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円')
 self.fileobj.write(b'377円')
 if fname:
 self.fileobj.write(fname + b'000円')

 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 if 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円' * 1024
 for i in range(count // 1024):
 self.write(chunk)
 self.write(b'0円' * (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円213円':
 raise BadGzipFile('Not a gzipped file (%r)' % magic)

 (method, flag,
 self._last_mtime) = struct.unpack("<BBIxx", self._read_exact(8))
 if method != 8:
 raise BadGzipFile('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円':
 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円':
 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 BadGzipFile("CRC check failed %s != %s" % (hex(crc32),
 hex(self._crc)))
 elif isize != (self._stream_size & 0xffffffff):
 raise BadGzipFile("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=_COMPRESS_LEVEL_BEST, *, mtime=None):
 """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, mtime=mtime) 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 main():
 from argparse import ArgumentParser
 parser = ArgumentParser(description=
 "A simple command line interface for the gzip module: act like gzip, "
 "but do not delete the input file.")
 group = parser.add_mutually_exclusive_group()
 group.add_argument('--fast', action='store_true', help='compress faster')
 group.add_argument('--best', action='store_true', help='compress better')
 group.add_argument("-d", "--decompress", action="store_true",
 help="act like gunzip instead of gzip")

 parser.add_argument("args", nargs="*", default=["-"], metavar='file')
 args = parser.parse_args()

 compresslevel = _COMPRESS_LEVEL_TRADEOFF
 if args.fast:
 compresslevel = _COMPRESS_LEVEL_FAST
 elif args.best:
 compresslevel = _COMPRESS_LEVEL_BEST

 for arg in args.args:
 if args.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,
 compresslevel=compresslevel)
 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__':
 main()