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bz2.py12.2 KB · 359 lines
"""Interface to the libbzip2 compression library. This module provides a file interface, classes for incremental(de)compression, and functions for one-shot (de)compression.""" __all__ = ["BZ2File", "BZ2Compressor", "BZ2Decompressor",           "open", "compress", "decompress"] __author__ = "Nadeem Vawda <nadeem.vawda@gmail.com>" from builtins import open as _builtin_openimport ioimport osimport _compressionfrom threading import RLock from _bz2 import BZ2Compressor, BZ2Decompressor  _MODE_CLOSED   = 0_MODE_READ     = 1# Value 2 no longer used_MODE_WRITE    = 3  class BZ2File(_compression.BaseStream):     """A file object providing transparent bzip2 (de)compression.     A BZ2File can act as a wrapper for an existing file object, or refer    directly to a named file on disk.     Note that BZ2File provides a *binary* file interface - data read is    returned as bytes, and data to be written should be given as bytes.    """     def __init__(self, filename, mode="r", *, compresslevel=9):        """Open a bzip2-compressed file.         If filename is a str, bytes, or PathLike object, it gives the        name of the file to be opened. Otherwise, it should be a file        object, which will be used to read or write the compressed data.         mode can be 'r' for reading (default), 'w' for (over)writing,        'x' for creating exclusively, or 'a' for appending. These can        equivalently be given as 'rb', 'wb', 'xb', and 'ab'.         If mode is 'w', 'x' or 'a', compresslevel can be a number between 1        and 9 specifying the level of compression: 1 produces the least        compression, and 9 (default) produces the most compression.         If mode is 'r', the input file may be the concatenation of        multiple compressed streams.        """        # This lock must be recursive, so that BufferedIOBase's        # writelines() does not deadlock.        self._lock = RLock()        self._fp = None        self._closefp = False        self._mode = _MODE_CLOSED         if not (1 <= compresslevel <= 9):            raise ValueError("compresslevel must be between 1 and 9")         if mode in ("", "r", "rb"):            mode = "rb"            mode_code = _MODE_READ        elif mode in ("w", "wb"):            mode = "wb"            mode_code = _MODE_WRITE            self._compressor = BZ2Compressor(compresslevel)        elif mode in ("x", "xb"):            mode = "xb"            mode_code = _MODE_WRITE            self._compressor = BZ2Compressor(compresslevel)        elif mode in ("a", "ab"):            mode = "ab"            mode_code = _MODE_WRITE            self._compressor = BZ2Compressor(compresslevel)        else:            raise ValueError("Invalid mode: %r" % (mode,))         if isinstance(filename, (str, bytes, os.PathLike)):            self._fp = _builtin_open(filename, mode)            self._closefp = True            self._mode = mode_code        elif hasattr(filename, "read") or hasattr(filename, "write"):            self._fp = filename            self._mode = mode_code        else:            raise TypeError("filename must be a str, bytes, file or PathLike object")         if self._mode == _MODE_READ:            raw = _compression.DecompressReader(self._fp,                BZ2Decompressor, trailing_error=OSError)            self._buffer = io.BufferedReader(raw)        else:            self._pos = 0     def close(self):        """Flush and close the file.         May be called more than once without error. Once the file is        closed, any other operation on it will raise a ValueError.        """        with self._lock:            if self._mode == _MODE_CLOSED:                return            try:                if self._mode == _MODE_READ:                    self._buffer.close()                elif self._mode == _MODE_WRITE:                    self._fp.write(self._compressor.flush())                    self._compressor = None            finally:                try:                    if self._closefp:                        self._fp.close()                finally:                    self._fp = None                    self._closefp = False                    self._mode = _MODE_CLOSED                    self._buffer = None     @property    def closed(self):        """True if this file is closed."""        return self._mode == _MODE_CLOSED     def fileno(self):        """Return the file descriptor for the underlying file."""        self._check_not_closed()        return self._fp.fileno()     def seekable(self):        """Return whether the file supports seeking."""        return self.readable() and self._buffer.seekable()     def readable(self):        """Return whether the file was opened for reading."""        self._check_not_closed()        return self._mode == _MODE_READ     def writable(self):        """Return whether the file was opened for writing."""        self._check_not_closed()        return self._mode == _MODE_WRITE     def peek(self, n=0):        """Return buffered data without advancing the file position.         Always returns at least one byte of data, unless at EOF.        The exact number of bytes returned is unspecified.        """        with self._lock:            self._check_can_read()            # Relies on the undocumented fact that BufferedReader.peek()            # always returns at least one byte (except at EOF), independent            # of the value of n            return self._buffer.peek(n)     def read(self, size=-1):        """Read up to size uncompressed bytes from the file.         If size is negative or omitted, read until EOF is reached.        Returns b'' if the file is already at EOF.        """        with self._lock:            self._check_can_read()            return self._buffer.read(size)     def read1(self, size=-1):        """Read up to size uncompressed bytes, while trying to avoid        making multiple reads from the underlying stream. Reads up to a        buffer's worth of data if size is negative.         Returns b'' if the file is at EOF.        """        with self._lock:            self._check_can_read()            if size < 0:                size = io.DEFAULT_BUFFER_SIZE            return self._buffer.read1(size)     def readinto(self, b):        """Read bytes into b.         Returns the number of bytes read (0 for EOF).        """        with self._lock:            self._check_can_read()            return self._buffer.readinto(b)     def readline(self, size=-1):        """Read a line of uncompressed bytes from the file.         The terminating newline (if present) is retained. If size is        non-negative, no more than size bytes will be read (in which        case the line may be incomplete). Returns b'' if already at EOF.        """        if not isinstance(size, int):            if not hasattr(size, "__index__"):                raise TypeError("Integer argument expected")            size = size.__index__()        with self._lock:            self._check_can_read()            return self._buffer.readline(size)     def readlines(self, size=-1):        """Read a list of lines of uncompressed bytes from the file.         size can be specified to control the number of lines read: no        further lines will be read once the total size of the lines read        so far equals or exceeds size.        """        if not isinstance(size, int):            if not hasattr(size, "__index__"):                raise TypeError("Integer argument expected")            size = size.__index__()        with self._lock:            self._check_can_read()            return self._buffer.readlines(size)     def write(self, data):        """Write a byte string to the file.         Returns the number of uncompressed bytes written, which is        always the length of data in bytes. Note that due to buffering,        the file on disk may not reflect the data written until close()        is called.        """        with self._lock:            self._check_can_write()            if isinstance(data, (bytes, bytearray)):                length = len(data)            else:                # accept any data that supports the buffer protocol                data = memoryview(data)                length = data.nbytes             compressed = self._compressor.compress(data)            self._fp.write(compressed)            self._pos += length            return length     def writelines(self, seq):        """Write a sequence of byte strings to the file.         Returns the number of uncompressed bytes written.        seq can be any iterable yielding byte strings.         Line separators are not added between the written byte strings.        """        with self._lock:            return _compression.BaseStream.writelines(self, seq)     def seek(self, offset, whence=io.SEEK_SET):        """Change the file position.         The new position is specified by offset, relative to the        position indicated by whence. Values for whence are:             0: start of stream (default); offset must not be negative            1: current stream position            2: end of stream; offset must not be positive         Returns the new file position.         Note that seeking is emulated, so depending on the parameters,        this operation may be extremely slow.        """        with self._lock:            self._check_can_seek()            return self._buffer.seek(offset, whence)     def tell(self):        """Return the current file position."""        with self._lock:            self._check_not_closed()            if self._mode == _MODE_READ:                return self._buffer.tell()            return self._pos  def open(filename, mode="rb", compresslevel=9,         encoding=None, errors=None, newline=None):    """Open a bzip2-compressed file in binary or text mode.     The filename argument can be an actual filename (a str, bytes, or    PathLike object), or an existing file object to read from or write    to.     The mode argument can be "r", "rb", "w", "wb", "x", "xb", "a" or    "ab" for binary mode, or "rt", "wt", "xt" or "at" for text mode.    The default mode is "rb", and the default compresslevel is 9.     For binary mode, this function is equivalent to the BZ2File    constructor: BZ2File(filename, mode, compresslevel). In this case,    the encoding, errors and newline arguments must not be provided.     For text mode, a BZ2File object is created, and wrapped in an    io.TextIOWrapper instance with the specified encoding, error    handling behavior, and line ending(s).     """    if "t" in mode:        if "b" in mode:            raise ValueError("Invalid mode: %r" % (mode,))    else:        if encoding is not None:            raise ValueError("Argument 'encoding' not supported in binary mode")        if errors is not None:            raise ValueError("Argument 'errors' not supported in binary mode")        if newline is not None:            raise ValueError("Argument 'newline' not supported in binary mode")     bz_mode = mode.replace("t", "")    binary_file = BZ2File(filename, bz_mode, compresslevel=compresslevel)     if "t" in mode:        return io.TextIOWrapper(binary_file, encoding, errors, newline)    else:        return binary_file  def compress(data, compresslevel=9):    """Compress a block of data.     compresslevel, if given, must be a number between 1 and 9.     For incremental compression, use a BZ2Compressor object instead.    """    comp = BZ2Compressor(compresslevel)    return comp.compress(data) + comp.flush()  def decompress(data):    """Decompress a block of data.     For incremental decompression, use a BZ2Decompressor object instead.    """    results = []    while data:        decomp = BZ2Decompressor()        try:            res = decomp.decompress(data)        except OSError:            if results:                break  # Leftover data is not a valid bzip2 stream; ignore it.            else:                raise  # Error on the first iteration; bail out.        results.append(res)        if not decomp.eof:            raise ValueError("Compressed data ended before the "                             "end-of-stream marker was reached")        data = decomp.unused_data    return b"".join(results)