mirror of
https://github.com/python/cpython.git
synced 2024-11-26 03:14:27 +08:00
447 lines
15 KiB
Python
447 lines
15 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
|
|
import zlib
|
|
import __builtin__
|
|
|
|
__all__ = ["GzipFile","open"]
|
|
|
|
FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
|
|
|
|
READ, WRITE = 1, 2
|
|
|
|
def write32(output, value):
|
|
output.write(struct.pack("<l", value))
|
|
|
|
def write32u(output, value):
|
|
if value < 0:
|
|
value = value + 0x100000000L
|
|
output.write(struct.pack("<L", value))
|
|
|
|
def read32(input):
|
|
return struct.unpack("<l", 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(), truncate(), and xreadlines() methods.
|
|
|
|
"""
|
|
|
|
myfileobj = None
|
|
|
|
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 = __builtin__.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 = ""
|
|
self.extrasize = 0
|
|
self.filename = filename
|
|
|
|
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()
|
|
|
|
def __repr__(self):
|
|
s = repr(self.fileobj)
|
|
return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
|
|
|
|
def _init_write(self, filename):
|
|
if filename[-3:] != '.gz':
|
|
filename = filename + '.gz'
|
|
self.filename = filename
|
|
self.crc = zlib.crc32("")
|
|
self.size = 0
|
|
self.writebuf = []
|
|
self.bufsize = 0
|
|
|
|
def _write_gzip_header(self):
|
|
self.fileobj.write('\037\213') # magic header
|
|
self.fileobj.write('\010') # compression method
|
|
fname = self.filename[:-3]
|
|
flags = 0
|
|
if fname:
|
|
flags = FNAME
|
|
self.fileobj.write(chr(flags))
|
|
write32u(self.fileobj, long(time.time()))
|
|
self.fileobj.write('\002')
|
|
self.fileobj.write('\377')
|
|
if fname:
|
|
self.fileobj.write(fname + '\000')
|
|
|
|
def _init_read(self):
|
|
self.crc = zlib.crc32("")
|
|
self.size = 0
|
|
|
|
def _read_gzip_header(self):
|
|
magic = self.fileobj.read(2)
|
|
if magic != '\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=='\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=='\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)
|
|
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, "write() on read-only GzipFile object")
|
|
|
|
if self.extrasize <= 0 and self.fileobj is None:
|
|
return ''
|
|
|
|
readsize = 1024
|
|
if size < 0: # get the whole thing
|
|
try:
|
|
while True:
|
|
self._read(readsize)
|
|
readsize = readsize * 2
|
|
except EOFError:
|
|
size = self.extrasize
|
|
else: # just get some more of it
|
|
try:
|
|
while size > self.extrasize:
|
|
self._read(readsize)
|
|
readsize = 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 == "":
|
|
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 != "":
|
|
# 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)
|
|
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.
|
|
self.fileobj.seek(-8, 1)
|
|
crc32 = read32(self.fileobj)
|
|
isize = read32(self.fileobj)
|
|
if crc32%0x100000000L != self.crc%0x100000000L:
|
|
raise ValueError, "CRC check failed"
|
|
elif isize != self.size:
|
|
raise ValueError, "Incorrect length of data produced"
|
|
|
|
def close(self):
|
|
if self.mode == WRITE:
|
|
self.fileobj.write(self.compress.flush())
|
|
write32(self.fileobj, self.crc)
|
|
write32(self.fileobj, self.size)
|
|
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):
|
|
self.fileobj.flush()
|
|
|
|
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 = ""
|
|
self.extrasize = 0
|
|
self.offset = 0
|
|
|
|
def seek(self, offset):
|
|
if self.mode == WRITE:
|
|
if offset < self.offset:
|
|
raise IOError('Negative seek in write mode')
|
|
count = offset - self.offset
|
|
for i in range(count/1024):
|
|
self.write(1024*'\0')
|
|
self.write((count%1024)*'\0')
|
|
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.maxint
|
|
bufs = []
|
|
readsize = min(100, size) # Read from the file in small chunks
|
|
while True:
|
|
if size == 0:
|
|
return "".join(bufs) # Return resulting line
|
|
|
|
c = self.read(readsize)
|
|
i = c.find('\n')
|
|
if size is not None:
|
|
# 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 i==-1 and len(c) > size: i=size-1
|
|
elif size <= i: i = size -1
|
|
|
|
if i >= 0 or c == '':
|
|
bufs.append(c[:i+1]) # Add portion of last chunk
|
|
self._unread(c[i+1:]) # Push back rest of chunk
|
|
return ''.join(bufs) # Return resulting line
|
|
|
|
# Append chunk to list, decrease 'size',
|
|
bufs.append(c)
|
|
size = size - len(c)
|
|
readsize = min(size, readsize * 2)
|
|
|
|
def readlines(self, sizehint=0):
|
|
# Negative numbers result in reading all the lines
|
|
if sizehint <= 0: sizehint = sys.maxint
|
|
L = []
|
|
while sizehint > 0:
|
|
line = self.readline()
|
|
if line == "": 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:", `arg`
|
|
continue
|
|
f = open(arg, "rb")
|
|
g = __builtin__.open(arg[:-3], "wb")
|
|
else:
|
|
if arg == "-":
|
|
f = sys.stdin
|
|
g = GzipFile(filename="", mode="wb", fileobj=sys.stdout)
|
|
else:
|
|
f = __builtin__.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()
|