393 lines
13 KiB
Python
393 lines
13 KiB
Python
"""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", "compress",
|
|
"decompress"]
|
|
|
|
__author__ = "Nadeem Vawda <nadeem.vawda@gmail.com>"
|
|
|
|
import io
|
|
import threading
|
|
import warnings
|
|
|
|
from _bz2 import BZ2Compressor, BZ2Decompressor
|
|
|
|
|
|
_MODE_CLOSED = 0
|
|
_MODE_READ = 1
|
|
_MODE_READ_EOF = 2
|
|
_MODE_WRITE = 3
|
|
|
|
_BUFFER_SIZE = 8192
|
|
|
|
|
|
class BZ2File(io.BufferedIOBase):
|
|
|
|
"""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=None, mode="r", buffering=None,
|
|
compresslevel=9, fileobj=None):
|
|
"""Open a bzip2-compressed file.
|
|
|
|
If filename is given, open the named file. Otherwise, operate on
|
|
the file object given by fileobj. Exactly one of these two
|
|
parameters should be provided.
|
|
|
|
mode can be 'r' for reading (default), or 'w' for writing.
|
|
|
|
buffering is ignored. Its use is deprecated.
|
|
|
|
If mode is 'w', 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.
|
|
"""
|
|
# This lock must be recursive, so that BufferedIOBase's
|
|
# readline(), readlines() and writelines() don't deadlock.
|
|
self._lock = threading.RLock()
|
|
self._fp = None
|
|
self._closefp = False
|
|
self._mode = _MODE_CLOSED
|
|
self._pos = 0
|
|
self._size = -1
|
|
|
|
if buffering is not None:
|
|
warnings.warn("Use of 'buffering' argument is deprecated",
|
|
DeprecationWarning)
|
|
|
|
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
|
|
self._decompressor = BZ2Decompressor()
|
|
self._buffer = None
|
|
elif mode in ("w", "wb"):
|
|
mode = "wb"
|
|
mode_code = _MODE_WRITE
|
|
self._compressor = BZ2Compressor()
|
|
else:
|
|
raise ValueError("Invalid mode: {!r}".format(mode))
|
|
|
|
if filename is not None and fileobj is None:
|
|
self._fp = open(filename, mode)
|
|
self._closefp = True
|
|
self._mode = mode_code
|
|
elif fileobj is not None and filename is None:
|
|
self._fp = fileobj
|
|
self._mode = mode_code
|
|
else:
|
|
raise ValueError("Must give exactly one of filename and fileobj")
|
|
|
|
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 in (_MODE_READ, _MODE_READ_EOF):
|
|
self._decompressor = None
|
|
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."""
|
|
return self._fp.fileno()
|
|
|
|
def seekable(self):
|
|
"""Return whether the file supports seeking."""
|
|
return self.readable()
|
|
|
|
def readable(self):
|
|
"""Return whether the file was opened for reading."""
|
|
return self._mode in (_MODE_READ, _MODE_READ_EOF)
|
|
|
|
def writable(self):
|
|
"""Return whether the file was opened for writing."""
|
|
return self._mode == _MODE_WRITE
|
|
|
|
# Mode-checking helper functions.
|
|
|
|
def _check_not_closed(self):
|
|
if self.closed:
|
|
raise ValueError("I/O operation on closed file")
|
|
|
|
def _check_can_read(self):
|
|
if not self.readable():
|
|
self._check_not_closed()
|
|
raise io.UnsupportedOperation("File not open for reading")
|
|
|
|
def _check_can_write(self):
|
|
if not self.writable():
|
|
self._check_not_closed()
|
|
raise io.UnsupportedOperation("File not open for writing")
|
|
|
|
def _check_can_seek(self):
|
|
if not self.seekable():
|
|
self._check_not_closed()
|
|
raise io.UnsupportedOperation("Seeking is only supported "
|
|
"on files open for reading")
|
|
|
|
# Fill the readahead buffer if it is empty. Returns False on EOF.
|
|
def _fill_buffer(self):
|
|
if self._buffer:
|
|
return True
|
|
if self._decompressor.eof:
|
|
self._mode = _MODE_READ_EOF
|
|
self._size = self._pos
|
|
return False
|
|
rawblock = self._fp.read(_BUFFER_SIZE)
|
|
if not rawblock:
|
|
raise EOFError("Compressed file ended before the "
|
|
"end-of-stream marker was reached")
|
|
self._buffer = self._decompressor.decompress(rawblock)
|
|
return True
|
|
|
|
# Read data until EOF.
|
|
# If return_data is false, consume the data without returning it.
|
|
def _read_all(self, return_data=True):
|
|
blocks = []
|
|
while self._fill_buffer():
|
|
if return_data:
|
|
blocks.append(self._buffer)
|
|
self._pos += len(self._buffer)
|
|
self._buffer = None
|
|
if return_data:
|
|
return b"".join(blocks)
|
|
|
|
# Read a block of up to n bytes.
|
|
# If return_data is false, consume the data without returning it.
|
|
def _read_block(self, n, return_data=True):
|
|
blocks = []
|
|
while n > 0 and self._fill_buffer():
|
|
if n < len(self._buffer):
|
|
data = self._buffer[:n]
|
|
self._buffer = self._buffer[n:]
|
|
else:
|
|
data = self._buffer
|
|
self._buffer = None
|
|
if return_data:
|
|
blocks.append(data)
|
|
self._pos += len(data)
|
|
n -= len(data)
|
|
if return_data:
|
|
return b"".join(blocks)
|
|
|
|
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()
|
|
if self._mode == _MODE_READ_EOF or not self._fill_buffer():
|
|
return b""
|
|
return self._buffer
|
|
|
|
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()
|
|
if self._mode == _MODE_READ_EOF or size == 0:
|
|
return b""
|
|
elif size < 0:
|
|
return self._read_all()
|
|
else:
|
|
return self._read_block(size)
|
|
|
|
def read1(self, size=-1):
|
|
"""Read up to size uncompressed bytes with at most one read
|
|
from the underlying stream.
|
|
|
|
Returns b'' if the file is at EOF.
|
|
"""
|
|
with self._lock:
|
|
self._check_can_read()
|
|
if (size == 0 or self._mode == _MODE_READ_EOF or
|
|
not self._fill_buffer()):
|
|
return b""
|
|
if 0 < size < len(self._buffer):
|
|
data = self._buffer[:size]
|
|
self._buffer = self._buffer[size:]
|
|
else:
|
|
data = self._buffer
|
|
self._buffer = None
|
|
self._pos += len(data)
|
|
return data
|
|
|
|
def readinto(self, b):
|
|
"""Read up to len(b) bytes into b.
|
|
|
|
Returns the number of bytes read (0 for EOF).
|
|
"""
|
|
with self._lock:
|
|
return io.BufferedIOBase.readinto(self, 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 hasattr(size, "__index__"):
|
|
raise TypeError("Integer argument expected")
|
|
size = size.__index__()
|
|
with self._lock:
|
|
return io.BufferedIOBase.readline(self, 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 hasattr(size, "__index__"):
|
|
raise TypeError("Integer argument expected")
|
|
size = size.__index__()
|
|
with self._lock:
|
|
return io.BufferedIOBase.readlines(self, size)
|
|
|
|
def write(self, data):
|
|
"""Write a byte string to the file.
|
|
|
|
Returns the number of uncompressed bytes written, which is
|
|
always len(data). 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()
|
|
compressed = self._compressor.compress(data)
|
|
self._fp.write(compressed)
|
|
self._pos += len(data)
|
|
return len(data)
|
|
|
|
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 io.BufferedIOBase.writelines(self, seq)
|
|
|
|
# Rewind the file to the beginning of the data stream.
|
|
def _rewind(self):
|
|
self._fp.seek(0, 0)
|
|
self._mode = _MODE_READ
|
|
self._pos = 0
|
|
self._decompressor = BZ2Decompressor()
|
|
self._buffer = None
|
|
|
|
def seek(self, offset, whence=0):
|
|
"""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()
|
|
|
|
# Recalculate offset as an absolute file position.
|
|
if whence == 0:
|
|
pass
|
|
elif whence == 1:
|
|
offset = self._pos + offset
|
|
elif whence == 2:
|
|
# Seeking relative to EOF - we need to know the file's size.
|
|
if self._size < 0:
|
|
self._read_all(return_data=False)
|
|
offset = self._size + offset
|
|
else:
|
|
raise ValueError("Invalid value for whence: {}".format(whence))
|
|
|
|
# Make it so that offset is the number of bytes to skip forward.
|
|
if offset < self._pos:
|
|
self._rewind()
|
|
else:
|
|
offset -= self._pos
|
|
|
|
# Read and discard data until we reach the desired position.
|
|
if self._mode != _MODE_READ_EOF:
|
|
self._read_block(offset, return_data=False)
|
|
|
|
return self._pos
|
|
|
|
def tell(self):
|
|
"""Return the current file position."""
|
|
with self._lock:
|
|
self._check_not_closed()
|
|
return self._pos
|
|
|
|
|
|
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.
|
|
"""
|
|
if len(data) == 0:
|
|
return b""
|
|
decomp = BZ2Decompressor()
|
|
result = decomp.decompress(data)
|
|
if not decomp.eof:
|
|
raise ValueError("Compressed data ended before the "
|
|
"end-of-stream marker was reached")
|
|
return result
|