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Jython is an implementation of the high-level, dynamic, object-oriented
language Python written in 100% Pure Java, and seamlessly integrated with
the Java platform. It thus allows you to run Python on any Java platform.
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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 io
import __builtin__
__all__ = ["GzipFile","open"]
FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
READ, WRITE = 1, 2
def write32u(output, value):
# The L format writes the bit pattern correctly whether signed
# or unsigned.
output.write(struct.pack("':
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 = ""
self.extrasize = 0
self.extrastart = 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
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):
s = repr(self.fileobj)
return ''
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("") & 0xffffffffL
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
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, str):
fname = fname.encode('latin-1')
if fname.endswith('.gz'):
fname = fname[:-3]
except UnicodeEncodeError:
fname = ''
flags = 0
if fname:
flags = FNAME
self.fileobj.write(chr(flags))
mtime = self.mtime
if mtime is None:
mtime = time.time()
write32u(self.fileobj, long(mtime))
self.fileobj.write('\002')
self.fileobj.write('\377')
if fname:
self.fileobj.write(fname + '\000')
def _init_read(self):
self.crc = zlib.crc32("") & 0xffffffffL
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) )
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=='\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):
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.fileobj.write(self.compress.compress(data))
self.size += len(data)
self.crc = zlib.crc32(data, self.crc) & 0xffffffffL
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 ''
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 _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.
#
# 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) & 0xffffffffL
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, 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 & 0xffffffffL):
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 = "\x00"
while c == "\x00":
c = self.fileobj.read(1)
if c:
self.fileobj.seek(-1, 1)
@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 2GB, or even 4GB
write32u(fileobj, self.size & 0xffffffffL)
finally:
myfileobj = self.myfileobj
if myfileobj:
self.myfileobj = None
myfileobj.close()
def __enter__(self):
# __enter__ is defined in _jyio._IOBase (aka
# org.python.modules._io.PyIOBase), but because we override
# the closed property in this class, we need to reproduce this
# method here for the calls to properly go through, much like
# the difference seen in _check_closed vs _checkClosed
self._check_closed()
return self
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 = ""
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
for i in xrange(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 xrange(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('\n', offset) + 1
if i > 0:
self.extrasize -= i - offset
self.offset += i - offset
return self.extrabuf[offset: i]
size = sys.maxint
readsize = self.min_readsize
else:
readsize = size
bufs = []
while size != 0:
c = self.read(readsize)
i = c.find('\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 == '':
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 ''.join(bufs) # Return resulting line
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 = __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()
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