mirror of
https://github.com/python/cpython.git
synced 2024-12-25 09:44:37 +08:00
626 lines
22 KiB
Python
626 lines
22 KiB
Python
"""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
|
|
|
|
__all__ = ["GzipFile", "open", "compress", "decompress"]
|
|
|
|
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 _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'', readprevious=False):
|
|
if self._read is None:
|
|
self._buffer = prepend
|
|
elif readprevious and len(prepend) <= self._read:
|
|
self._read -= len(prepend)
|
|
return
|
|
else:
|
|
self._buffer = self._buffer[read:] + prepend
|
|
self._length = len(self._buffer)
|
|
self._read = 0
|
|
|
|
def unused(self):
|
|
if self._read is None:
|
|
return b''
|
|
return self._buffer[self._read:]
|
|
|
|
def seek(self, offset, whence=0):
|
|
# This is only ever called with offset=whence=0
|
|
if whence == 1 and self._read is not None:
|
|
if 0 <= offset + self._read <= self._length:
|
|
self._read += offset
|
|
return
|
|
else:
|
|
offset += self._length - self._read
|
|
self._read = None
|
|
self._buffer = None
|
|
return self.file.seek(offset, whence)
|
|
|
|
def __getattr__(self, name):
|
|
return getattr(name, self.file)
|
|
|
|
|
|
class GzipFile(io.BufferedIOBase):
|
|
"""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, 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, 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.
|
|
|
|
The mtime argument is an optional numeric timestamp to be written
|
|
to the stream when compressing. All gzip compressed streams
|
|
are required to contain a timestamp. If omitted or None, the
|
|
current time is used. This module ignores the timestamp when
|
|
decompressing; however, some programs, such as gunzip, make use
|
|
of it. The format of the timestamp is the same as that of the
|
|
return value of time.time() and of the st_mtime member of the
|
|
object returned by os.stat().
|
|
|
|
"""
|
|
|
|
# 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
|
|
# Buffer data read from gzip file. extrastart is offset in
|
|
# stream where buffer starts. extrasize is number of
|
|
# bytes remaining in buffer from current stream position.
|
|
self.extrabuf = b""
|
|
self.extrasize = 0
|
|
self.extrastart = 0
|
|
self.name = filename
|
|
# Starts small, scales exponentially
|
|
self.min_readsize = 100
|
|
fileobj = _PaddedFile(fileobj)
|
|
|
|
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
|
|
self.mtime = mtime
|
|
|
|
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
|
|
|
|
def __repr__(self):
|
|
fileobj = self.fileobj
|
|
if isinstance(fileobj, _PaddedFile):
|
|
fileobj = fileobj.file
|
|
s = repr(fileobj)
|
|
return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
|
|
|
|
def _check_closed(self):
|
|
"""Raises a ValueError if the underlying file object has been closed.
|
|
|
|
"""
|
|
if self.closed:
|
|
raise ValueError('I/O operation on closed file.')
|
|
|
|
def _init_write(self, filename):
|
|
self.name = filename
|
|
self.crc = zlib.crc32(b"") & 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 = os.path.basename(self.name)
|
|
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.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 _init_read(self):
|
|
self.crc = zlib.crc32(b"") & 0xffffffff
|
|
self.size = 0
|
|
|
|
def _read_gzip_header(self):
|
|
magic = self.fileobj.read(2)
|
|
if magic == b'':
|
|
raise EOFError("Reached EOF")
|
|
|
|
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) )
|
|
self.mtime = read32(self.fileobj)
|
|
# extraflag = self.fileobj.read(1)
|
|
# os = self.fileobj.read(1)
|
|
self.fileobj.read(2)
|
|
|
|
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
|
|
|
|
unused = self.fileobj.unused()
|
|
if unused:
|
|
uncompress = self.decompress.decompress(unused)
|
|
self._add_read_data(uncompress)
|
|
|
|
def write(self,data):
|
|
self._check_closed()
|
|
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")
|
|
|
|
# Convert data type if called by io.BufferedWriter.
|
|
if isinstance(data, memoryview):
|
|
data = data.tobytes()
|
|
|
|
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)
|
|
|
|
return len(data)
|
|
|
|
def read(self, size=-1):
|
|
self._check_closed()
|
|
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
|
|
|
|
offset = self.offset - self.extrastart
|
|
chunk = self.extrabuf[offset: offset + size]
|
|
self.extrasize = self.extrasize - size
|
|
|
|
self.offset += size
|
|
return chunk
|
|
|
|
def peek(self, n):
|
|
if self.mode != READ:
|
|
import errno
|
|
raise IOError(errno.EBADF, "peek() on write-only GzipFile object")
|
|
|
|
# Do not return ridiculously small buffers, for one common idiom
|
|
# is to call peek(1) and expect more bytes in return.
|
|
if n < 100:
|
|
n = 100
|
|
if self.extrasize == 0:
|
|
if self.fileobj is None:
|
|
return b''
|
|
try:
|
|
# 1024 is the same buffering heuristic used in read()
|
|
self._read(max(n, 1024))
|
|
except EOFError:
|
|
pass
|
|
offset = self.offset - self.extrastart
|
|
remaining = self.extrasize
|
|
assert remaining == len(self.extrabuf) - offset
|
|
return self.extrabuf[offset:offset + n]
|
|
|
|
def _unread(self, buf):
|
|
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.
|
|
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()
|
|
# Prepend the already read bytes to the fileobj to they can be
|
|
# seen by _read_eof()
|
|
self.fileobj.prepend(self.decompress.unused_data, True)
|
|
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.
|
|
# Prepend the already read bytes to the fileobj to they can be
|
|
# seen by _read_eof() and _read_gzip_header()
|
|
self.fileobj.prepend(self.decompress.unused_data, True)
|
|
# 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
|
|
offset = self.offset - self.extrastart
|
|
self.extrabuf = self.extrabuf[offset:] + data
|
|
self.extrasize = self.extrasize + len(data)
|
|
self.extrastart = self.offset
|
|
self.size = self.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 = 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")
|
|
|
|
# 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.fileobj.read(1)
|
|
if c:
|
|
self.fileobj.prepend(c, True)
|
|
|
|
@property
|
|
def closed(self):
|
|
return self.fileobj is None
|
|
|
|
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 flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
|
|
self._check_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 IOError("Can't rewind in write mode")
|
|
self.fileobj.seek(0)
|
|
self._new_member = True
|
|
self.extrabuf = b""
|
|
self.extrasize = 0
|
|
self.extrastart = 0
|
|
self.offset = 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=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)
|
|
|
|
return self.offset
|
|
|
|
def readline(self, size=-1):
|
|
if size < 0:
|
|
# Shortcut common case - newline found in buffer.
|
|
offset = self.offset - self.extrastart
|
|
i = self.extrabuf.find(b'\n', offset) + 1
|
|
if i > 0:
|
|
self.extrasize -= i - offset
|
|
self.offset += i - offset
|
|
return self.extrabuf[offset: i]
|
|
|
|
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 compress(data, compresslevel=9):
|
|
"""Compress data in one shot and return the compressed string.
|
|
Optional argument is the compression level, in range of 1-9.
|
|
"""
|
|
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:
|
|
g.close()
|
|
if f is not sys.stdin:
|
|
f.close()
|
|
|
|
if __name__ == '__main__':
|
|
_test()
|