| """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): |
| return GzipFile(filename, mode, compresslevel) |
| |
| class GzipFile: |
| |
| myfileobj = None |
| |
| def __init__(self, filename=None, mode=None, |
| compresslevel=9, fileobj=None): |
| 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 = 1 |
| 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 ValueError, "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 (1): |
| 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 (1): |
| 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.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.extrasize <= 0 and self.fileobj is None: |
| return '' |
| |
| readsize = 1024 |
| if size < 0: # get the whole thing |
| try: |
| while 1: |
| 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 = 0 |
| |
| # 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 = 1 |
| |
| 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 0 |
| |
| 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 = 1 |
| 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 1: |
| 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 _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 1: |
| 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() |