mirror of
https://github.com/python/cpython.git
synced 2025-07-08 03:45:36 +00:00
54f22ed30b
who writes: Here is batch 2, as a big collection of CVS context diffs. Along with moving comments into docstrings, i've added a couple of missing docstrings and attempted to make sure more module docstrings begin with a one-line summary. I did not add docstrings to the methods in profile.py for fear of upsetting any careful optimizations there, though i did move class documentation into class docstrings. The convention i'm using is to leave credits/version/copyright type of stuff in # comments, and move the rest of the descriptive stuff about module usage into module docstrings. Hope this is okay.
338 lines
11 KiB
Python
338 lines
11 KiB
Python
"""This module implements a function that reads and writes a gzipped file.
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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 time
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import string
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import zlib
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import struct
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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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#
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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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if (self.myfileobj is not None or
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self.fileobj is not None):
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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):
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bufs = []
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readsize = 100
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while 1:
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c = self.read(readsize)
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i = string.find(c, '\n')
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if i >= 0 or c == '':
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bufs.append(c[:i+1])
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self._unread(c[i+1:])
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return string.join(bufs, '')
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bufs.append(c)
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readsize = readsize * 2
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def readlines(self, ignored=None):
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buf = self.read()
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lines = string.split(buf, '\n')
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for i in range(len(lines)-1):
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lines[i] = lines[i] + '\n'
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if lines and not lines[-1]:
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del lines[-1]
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return lines
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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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