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Diffstat (limited to 'lib/python2.7/gzip.py')
| -rw-r--r-- | lib/python2.7/gzip.py | 518 |
1 files changed, 518 insertions, 0 deletions
diff --git a/lib/python2.7/gzip.py b/lib/python2.7/gzip.py new file mode 100644 index 0000000..a613bae --- /dev/null +++ b/lib/python2.7/gzip.py @@ -0,0 +1,518 @@ +"""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("<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 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 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 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(). + + """ + + # Make sure we don't inadvertently enable universal newlines on the + # underlying file object - in read mode, this causes data corruption. + if mode: + mode = mode.replace('U', '') + # 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: + # Issue #13781: os.fdopen() creates a fileobj with a bogus name + # attribute. Avoid saving this in the gzip header's filename field. + if hasattr(fileobj, 'name') and fileobj.name != '<fdopen>': + 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 = "" + 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 '<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("") & 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 + fname = os.path.basename(self.name) + if fname.endswith(".gz"): + fname = fname[:-3] + 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.size = self.size + len(data) + self.crc = zlib.crc32(data, self.crc) & 0xffffffffL + 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 '' + + 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): + 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 & 0xffffffffL) + 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 = "" + 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() |