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41616ee194
.readlines() methods. Inspired by a patch from Wolfgang Grafen, though this version of the patch was completely rewritten from his code.
362 lines
12 KiB
Python
362 lines
12 KiB
Python
"""Functions that read and write gzipped files.
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The user of the file doesn't have to worry about the compression,
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but random access is not allowed."""
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# based on Andrew Kuchling's minigzip.py distributed with the zlib module
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import string, struct, sys, time
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import zlib
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import __builtin__
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FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
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READ, WRITE = 1, 2
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def write32(output, value):
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output.write(struct.pack("<l", value))
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def write32u(output, value):
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output.write(struct.pack("<L", value))
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def read32(input):
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return struct.unpack("<l", input.read(4))[0]
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def open(filename, mode="rb", compresslevel=9):
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return GzipFile(filename, mode, compresslevel)
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class GzipFile:
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myfileobj = None
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def __init__(self, filename=None, mode=None,
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compresslevel=9, fileobj=None):
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if fileobj is None:
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fileobj = self.myfileobj = __builtin__.open(filename, mode or 'rb')
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if filename is None:
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if hasattr(fileobj, 'name'): filename = fileobj.name
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else: filename = ''
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if mode is None:
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if hasattr(fileobj, 'mode'): mode = fileobj.mode
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else: mode = 'rb'
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if mode[0:1] == 'r':
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self.mode = READ
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# Set flag indicating start of a new member
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self._new_member = 1
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self.extrabuf = ""
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self.extrasize = 0
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self.filename = filename
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elif mode[0:1] == 'w' or mode[0:1] == 'a':
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self.mode = WRITE
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self._init_write(filename)
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self.compress = zlib.compressobj(compresslevel,
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zlib.DEFLATED,
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-zlib.MAX_WBITS,
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zlib.DEF_MEM_LEVEL,
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0)
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else:
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raise ValueError, "Mode " + mode + " not supported"
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self.fileobj = fileobj
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if self.mode == WRITE:
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self._write_gzip_header()
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def __repr__(self):
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s = repr(self.fileobj)
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return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
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def _init_write(self, filename):
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if filename[-3:] != '.gz':
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filename = filename + '.gz'
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self.filename = filename
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self.crc = zlib.crc32("")
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self.size = 0
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self.writebuf = []
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self.bufsize = 0
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def _write_gzip_header(self):
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self.fileobj.write('\037\213') # magic header
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self.fileobj.write('\010') # compression method
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fname = self.filename[:-3]
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flags = 0
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if fname:
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flags = FNAME
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self.fileobj.write(chr(flags))
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write32u(self.fileobj, long(time.time()))
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self.fileobj.write('\002')
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self.fileobj.write('\377')
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if fname:
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self.fileobj.write(fname + '\000')
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def _init_read(self):
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self.crc = zlib.crc32("")
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self.size = 0
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def _read_gzip_header(self):
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magic = self.fileobj.read(2)
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if magic != '\037\213':
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raise IOError, 'Not a gzipped file'
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method = ord( self.fileobj.read(1) )
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if method != 8:
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raise IOError, 'Unknown compression method'
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flag = ord( self.fileobj.read(1) )
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# modtime = self.fileobj.read(4)
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# extraflag = self.fileobj.read(1)
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# os = self.fileobj.read(1)
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self.fileobj.read(6)
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if flag & FEXTRA:
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# Read & discard the extra field, if present
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xlen=ord(self.fileobj.read(1))
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xlen=xlen+256*ord(self.fileobj.read(1))
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self.fileobj.read(xlen)
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if flag & FNAME:
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# Read and discard a null-terminated string containing the filename
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while (1):
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s=self.fileobj.read(1)
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if not s or s=='\000': break
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if flag & FCOMMENT:
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# Read and discard a null-terminated string containing a comment
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while (1):
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s=self.fileobj.read(1)
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if not s or s=='\000': break
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if flag & FHCRC:
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self.fileobj.read(2) # Read & discard the 16-bit header CRC
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def write(self,data):
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if self.fileobj is None:
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raise ValueError, "write() on closed GzipFile object"
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if len(data) > 0:
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self.size = self.size + len(data)
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self.crc = zlib.crc32(data, self.crc)
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self.fileobj.write( self.compress.compress(data) )
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def writelines(self,lines):
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self.write(string.join(lines))
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def read(self, size=-1):
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if self.extrasize <= 0 and self.fileobj is None:
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return ''
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readsize = 1024
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if size < 0: # get the whole thing
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try:
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while 1:
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self._read(readsize)
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readsize = readsize * 2
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except EOFError:
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size = self.extrasize
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else: # just get some more of it
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try:
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while size > self.extrasize:
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self._read(readsize)
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readsize = readsize * 2
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except EOFError:
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if size > self.extrasize:
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size = self.extrasize
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chunk = self.extrabuf[:size]
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self.extrabuf = self.extrabuf[size:]
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self.extrasize = self.extrasize - size
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return chunk
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def _unread(self, buf):
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self.extrabuf = buf + self.extrabuf
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self.extrasize = len(buf) + self.extrasize
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def _read(self, size=1024):
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if self.fileobj is None: raise EOFError, "Reached EOF"
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if self._new_member:
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# If the _new_member flag is set, we have to
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# jump to the next member, if there is one.
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#
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# First, check if we're at the end of the file;
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# if so, it's time to stop; no more members to read.
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pos = self.fileobj.tell() # Save current position
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self.fileobj.seek(0, 2) # Seek to end of file
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if pos == self.fileobj.tell():
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self.fileobj = None
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raise EOFError, "Reached EOF"
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else:
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self.fileobj.seek( pos ) # Return to original position
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self._init_read()
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self._read_gzip_header()
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self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
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self._new_member = 0
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# Read a chunk of data from the file
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buf = self.fileobj.read(size)
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# If the EOF has been reached, flush the decompression object
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# and mark this object as finished.
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if buf == "":
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uncompress = self.decompress.flush()
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self._read_eof()
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self.fileobj = None
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self._add_read_data( uncompress )
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raise EOFError, 'Reached EOF'
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uncompress = self.decompress.decompress(buf)
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self._add_read_data( uncompress )
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if self.decompress.unused_data != "":
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# Ending case: we've come to the end of a member in the file,
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# so seek back to the start of the unused data, finish up
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# this member, and read a new gzip header.
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# (The number of bytes to seek back is the length of the unused
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# data, minus 8 because _read_eof() will rewind a further 8 bytes)
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self.fileobj.seek( -len(self.decompress.unused_data)+8, 1)
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# Check the CRC and file size, and set the flag so we read
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# a new member on the next call
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self._read_eof()
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self._new_member = 1
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def _add_read_data(self, data):
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self.crc = zlib.crc32(data, self.crc)
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self.extrabuf = self.extrabuf + data
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self.extrasize = self.extrasize + len(data)
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self.size = self.size + len(data)
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def _read_eof(self):
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# We've read to the end of the file, so we have to rewind in order
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# to reread the 8 bytes containing the CRC and the file size.
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# We check the that the computed CRC and size of the
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# uncompressed data matches the stored values.
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self.fileobj.seek(-8, 1)
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crc32 = read32(self.fileobj)
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isize = read32(self.fileobj)
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if crc32%0x100000000L != self.crc%0x100000000L:
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raise ValueError, "CRC check failed"
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elif isize != self.size:
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raise ValueError, "Incorrect length of data produced"
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def close(self):
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if self.mode == WRITE:
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self.fileobj.write(self.compress.flush())
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write32(self.fileobj, self.crc)
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write32(self.fileobj, self.size)
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self.fileobj = None
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elif self.mode == READ:
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self.fileobj = None
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if self.myfileobj:
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self.myfileobj.close()
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self.myfileobj = None
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def __del__(self):
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try:
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if (self.myfileobj is None and
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self.fileobj is None):
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return
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except AttributeError:
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return
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self.close()
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def flush(self):
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self.fileobj.flush()
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def seek(self):
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raise IOError, 'Random access not allowed in gzip files'
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def tell(self):
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raise IOError, 'I won\'t tell() you for gzip files'
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def isatty(self):
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return 0
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def readline(self, size=-1):
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if size < 0: size = sys.maxint
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bufs = []
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orig_size = size
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readsize = min(100, size) # Read from the file in small chunks
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while 1:
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if size == 0:
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return string.join(bufs, '') # Return resulting line
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c = self.read(readsize)
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i = string.find(c, '\n')
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if size is not None:
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# We set i=size to break out of the loop under two
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# conditions: 1) there's no newline, and the chunk is
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# larger than size, or 2) there is a newline, but the
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# resulting line would be longer than 'size'.
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if i==-1 and len(c) > size: i=size-1
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elif size <= i: i = size -1
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if i >= 0 or c == '':
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bufs.append(c[:i+1]) # Add portion of last chunk
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self._unread(c[i+1:]) # Push back rest of chunk
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return string.join(bufs, '') # Return resulting line
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# Append chunk to list, decrease 'size',
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bufs.append(c)
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size = size - len(c)
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readsize = min(size, readsize * 2)
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def readlines(self, sizehint=0):
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# Negative numbers result in reading all the lines
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if sizehint <= 0: sizehint = sys.maxint
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L = []
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while sizehint > 0:
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line = self.readline()
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if line == "": break
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L.append( line )
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sizehint = sizehint - len(line)
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return L
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def writelines(self, L):
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for line in L:
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self.write(line)
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def _test():
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# Act like gzip; with -d, act like gunzip.
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# The input file is not deleted, however, nor are any other gzip
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# options or features supported.
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import sys
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args = sys.argv[1:]
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decompress = args and args[0] == "-d"
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if decompress:
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args = args[1:]
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if not args:
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args = ["-"]
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for arg in args:
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if decompress:
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if arg == "-":
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f = GzipFile(filename="", mode="rb", fileobj=sys.stdin)
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g = sys.stdout
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else:
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if arg[-3:] != ".gz":
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print "filename doesn't end in .gz:", `arg`
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continue
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f = open(arg, "rb")
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g = __builtin__.open(arg[:-3], "wb")
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else:
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if arg == "-":
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f = sys.stdin
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g = GzipFile(filename="", mode="wb", fileobj=sys.stdout)
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else:
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f = __builtin__.open(arg, "rb")
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g = open(arg + ".gz", "wb")
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while 1:
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chunk = f.read(1024)
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if not chunk:
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break
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g.write(chunk)
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if g is not sys.stdout:
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g.close()
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if f is not sys.stdin:
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f.close()
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if __name__ == '__main__':
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_test()
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