Issue #5863: Rewrite BZ2File in pure Python, and allow it to accept

file-like objects using a new `fileobj` constructor argument.  Patch by
Nadeem Vawda.

Lib/bz2.py

@@ -0,0 +1,392 @@
+"""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 opening 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

Lib/test/test_bz2.py

@@ -21,7 +21,30 @@ has_cmdline_bunzip2 = sys.platform not in ("win32", "os2emx")
 
 class BaseTest(unittest.TestCase):
     "Base for other testcases."
-    TEXT = b'root:x:0:0:root:/root:/bin/bash\nbin:x:1:1:bin:/bin:\ndaemon:x:2:2:daemon:/sbin:\nadm:x:3:4:adm:/var/adm:\nlp:x:4:7:lp:/var/spool/lpd:\nsync:x:5:0:sync:/sbin:/bin/sync\nshutdown:x:6:0:shutdown:/sbin:/sbin/shutdown\nhalt:x:7:0:halt:/sbin:/sbin/halt\nmail:x:8:12:mail:/var/spool/mail:\nnews:x:9:13:news:/var/spool/news:\nuucp:x:10:14:uucp:/var/spool/uucp:\noperator:x:11:0:operator:/root:\ngames:x:12:100:games:/usr/games:\ngopher:x:13:30:gopher:/usr/lib/gopher-data:\nftp:x:14:50:FTP User:/var/ftp:/bin/bash\nnobody:x:65534:65534:Nobody:/home:\npostfix:x:100:101:postfix:/var/spool/postfix:\nniemeyer:x:500:500::/home/niemeyer:/bin/bash\npostgres:x:101:102:PostgreSQL Server:/var/lib/pgsql:/bin/bash\nmysql:x:102:103:MySQL server:/var/lib/mysql:/bin/bash\nwww:x:103:104::/var/www:/bin/false\n'
+    TEXT_LINES = [
+        b'root:x:0:0:root:/root:/bin/bash\n',
+        b'bin:x:1:1:bin:/bin:\n',
+        b'daemon:x:2:2:daemon:/sbin:\n',
+        b'adm:x:3:4:adm:/var/adm:\n',
+        b'lp:x:4:7:lp:/var/spool/lpd:\n',
+        b'sync:x:5:0:sync:/sbin:/bin/sync\n',
+        b'shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown\n',
+        b'halt:x:7:0:halt:/sbin:/sbin/halt\n',
+        b'mail:x:8:12:mail:/var/spool/mail:\n',
+        b'news:x:9:13:news:/var/spool/news:\n',
+        b'uucp:x:10:14:uucp:/var/spool/uucp:\n',
+        b'operator:x:11:0:operator:/root:\n',
+        b'games:x:12:100:games:/usr/games:\n',
+        b'gopher:x:13:30:gopher:/usr/lib/gopher-data:\n',
+        b'ftp:x:14:50:FTP User:/var/ftp:/bin/bash\n',
+        b'nobody:x:65534:65534:Nobody:/home:\n',
+        b'postfix:x:100:101:postfix:/var/spool/postfix:\n',
+        b'niemeyer:x:500:500::/home/niemeyer:/bin/bash\n',
+        b'postgres:x:101:102:PostgreSQL Server:/var/lib/pgsql:/bin/bash\n',
+        b'mysql:x:102:103:MySQL server:/var/lib/mysql:/bin/bash\n',
+        b'www:x:103:104::/var/www:/bin/false\n',
+        ]
+    TEXT = b''.join(TEXT_LINES)
     DATA = b'BZh91AY&SY.\xc8N\x18\x00\x01>_\x80\x00\x10@\x02\xff\xf0\x01\x07n\x00?\xe7\xff\xe00\x01\x99\xaa\x00\xc0\x03F\x86\x8c#&\x83F\x9a\x03\x06\xa6\xd0\xa6\x93M\x0fQ\xa7\xa8\x06\x804hh\x12$\x11\xa4i4\xf14S\xd2<Q\xb5\x0fH\xd3\xd4\xdd\xd5\x87\xbb\xf8\x94\r\x8f\xafI\x12\xe1\xc9\xf8/E\x00pu\x89\x12]\xc9\xbbDL\nQ\x0e\t1\x12\xdf\xa0\xc0\x97\xac2O9\x89\x13\x94\x0e\x1c7\x0ed\x95I\x0c\xaaJ\xa4\x18L\x10\x05#\x9c\xaf\xba\xbc/\x97\x8a#C\xc8\xe1\x8cW\xf9\xe2\xd0\xd6M\xa7\x8bXa<e\x84t\xcbL\xb3\xa7\xd9\xcd\xd1\xcb\x84.\xaf\xb3\xab\xab\xad`n}\xa0lh\tE,\x8eZ\x15\x17VH>\x88\xe5\xcd9gd6\x0b\n\xe9\x9b\xd5\x8a\x99\xf7\x08.K\x8ev\xfb\xf7xw\xbb\xdf\xa1\x92\xf1\xdd|/";\xa2\xba\x9f\xd5\xb1#A\xb6\xf6\xb3o\xc9\xc5y\\\xebO\xe7\x85\x9a\xbc\xb6f8\x952\xd5\xd7"%\x89>V,\xf7\xa6z\xe2\x9f\xa3\xdf\x11\x11"\xd6E)I\xa9\x13^\xca\xf3r\xd0\x03U\x922\xf26\xec\xb6\xed\x8b\xc3U\x13\x9d\xc5\x170\xa4\xfa^\x92\xacDF\x8a\x97\xd6\x19\xfe\xdd\xb8\xbd\x1a\x9a\x19\xa3\x80ankR\x8b\xe5\xd83]\xa9\xc6\x08\x82f\xf6\xb9"6l$\xb8j@\xc0\x8a\xb0l1..\xbak\x83ls\x15\xbc\xf4\xc1\x13\xbe\xf8E\xb8\x9d\r\xa8\x9dk\x84\xd3n\xfa\xacQ\x07\xb1%y\xaav\xb4\x08\xe0z\x1b\x16\xf5\x04\xe9\xcc\xb9\x08z\x1en7.G\xfc]\xc9\x14\xe1B@\xbb!8`'
     DATA_CRLF = b'BZh91AY&SY\xaez\xbbN\x00\x01H\xdf\x80\x00\x12@\x02\xff\xf0\x01\x07n\x00?\xe7\xff\xe0@\x01\xbc\xc6`\x86*\x8d=M\xa9\x9a\x86\xd0L@\x0fI\xa6!\xa1\x13\xc8\x88jdi\x8d@\x03@\x1a\x1a\x0c\x0c\x83 \x00\xc4h2\x19\x01\x82D\x84e\t\xe8\x99\x89\x19\x1ah\x00\r\x1a\x11\xaf\x9b\x0fG\xf5(\x1b\x1f?\t\x12\xcf\xb5\xfc\x95E\x00ps\x89\x12^\xa4\xdd\xa2&\x05(\x87\x04\x98\x89u\xe40%\xb6\x19\'\x8c\xc4\x89\xca\x07\x0e\x1b!\x91UIFU%C\x994!DI\xd2\xfa\xf0\xf1N8W\xde\x13A\xf5\x9cr%?\x9f3;I45A\xd1\x8bT\xb1<l\xba\xcb_\xc00xY\x17r\x17\x88\x08\x08@\xa0\ry@\x10\x04$)`\xf2\xce\x89z\xb0s\xec\x9b.iW\x9d\x81\xb5-+t\x9f\x1a\'\x97dB\xf5x\xb5\xbe.[.\xd7\x0e\x81\xe7\x08\x1cN`\x88\x10\xca\x87\xc3!"\x80\x92R\xa1/\xd1\xc0\xe6mf\xac\xbd\x99\xcca\xb3\x8780>\xa4\xc7\x8d\x1a\\"\xad\xa1\xabyBg\x15\xb9l\x88\x88\x91k"\x94\xa4\xd4\x89\xae*\xa6\x0b\x10\x0c\xd6\xd4m\xe86\xec\xb5j\x8a\x86j\';\xca.\x01I\xf2\xaaJ\xe8\x88\x8cU+t3\xfb\x0c\n\xa33\x13r2\r\x16\xe0\xb3(\xbf\x1d\x83r\xe7M\xf0D\x1365\xd8\x88\xd3\xa4\x92\xcb2\x06\x04\\\xc1\xb0\xea//\xbek&\xd8\xe6+t\xe5\xa1\x13\xada\x16\xder5"w]\xa2i\xb7[\x97R \xe2IT\xcd;Z\x04dk4\xad\x8a\t\xd3\x81z\x10\xf1:^`\xab\x1f\xc5\xdc\x91N\x14$+\x9e\xae\xd3\x80'
 
@@ -54,13 +77,15 @@ class BZ2FileTest(BaseTest):
         if os.path.isfile(self.filename):
             os.unlink(self.filename)
 
-    def createTempFile(self, crlf=0):
+    def getData(self, crlf=False):
+        if crlf:
+            return self.DATA_CRLF
+        else:
+            return self.DATA
+
+    def createTempFile(self, crlf=False):
         with open(self.filename, "wb") as f:
-            if crlf:
-                data = self.DATA_CRLF
-            else:
-                data = self.DATA
-            f.write(data)
+            f.write(self.getData(crlf))
 
     def testRead(self):
         # "Test BZ2File.read()"
@@ -70,7 +95,7 @@ class BZ2FileTest(BaseTest):
             self.assertEqual(bz2f.read(), self.TEXT)
 
     def testRead0(self):
-        # Test BBZ2File.read(0)"
+        # "Test BBZ2File.read(0)"
         self.createTempFile()
         with BZ2File(self.filename) as bz2f:
             self.assertRaises(TypeError, bz2f.read, None)
@@ -94,6 +119,28 @@ class BZ2FileTest(BaseTest):
         with BZ2File(self.filename) as bz2f:
             self.assertEqual(bz2f.read(100), self.TEXT[:100])
 
+    def testPeek(self):
+        # "Test BZ2File.peek()"
+        self.createTempFile()
+        with BZ2File(self.filename) as bz2f:
+            pdata = bz2f.peek()
+            self.assertNotEqual(len(pdata), 0)
+            self.assertTrue(self.TEXT.startswith(pdata))
+            self.assertEqual(bz2f.read(), self.TEXT)
+
+    def testReadInto(self):
+        # "Test BZ2File.readinto()"
+        self.createTempFile()
+        with BZ2File(self.filename) as bz2f:
+            n = 128
+            b = bytearray(n)
+            self.assertEqual(bz2f.readinto(b), n)
+            self.assertEqual(b, self.TEXT[:n])
+            n = len(self.TEXT) - n
+            b = bytearray(len(self.TEXT))
+            self.assertEqual(bz2f.readinto(b), n)
+            self.assertEqual(b[:n], self.TEXT[-n:])
+
     def testReadLine(self):
         # "Test BZ2File.readline()"
         self.createTempFile()
@@ -125,7 +172,7 @@ class BZ2FileTest(BaseTest):
         bz2f = BZ2File(self.filename)
         bz2f.close()
         self.assertRaises(ValueError, bz2f.__next__)
-        # This call will deadlock of the above .__next__ call failed to
+        # This call will deadlock if the above .__next__ call failed to
         # release the lock.
         self.assertRaises(ValueError, bz2f.readlines)
 
@@ -217,6 +264,13 @@ class BZ2FileTest(BaseTest):
             self.assertEqual(bz2f.tell(), 0)
             self.assertEqual(bz2f.read(), self.TEXT)
 
+    def testFileno(self):
+        # "Test BZ2File.fileno()"
+        self.createTempFile()
+        with open(self.filename) as rawf:
+            with BZ2File(fileobj=rawf) as bz2f:
+                self.assertEqual(bz2f.fileno(), rawf.fileno())
+
     def testOpenDel(self):
         # "Test opening and deleting a file many times"
         self.createTempFile()
@@ -278,17 +332,65 @@ class BZ2FileTest(BaseTest):
                 t.join()
 
     def testMixedIterationReads(self):
-        # Issue #8397: mixed iteration and reads should be forbidden.
-        with bz2.BZ2File(self.filename, 'wb') as f:
-            # The internal buffer size is hard-wired to 8192 bytes, we must
-            # write out more than that for the test to stop half through
-            # the buffer.
-            f.write(self.TEXT * 100)
-        with bz2.BZ2File(self.filename, 'rb') as f:
-            next(f)
-            self.assertRaises(ValueError, f.read)
-            self.assertRaises(ValueError, f.readline)
-            self.assertRaises(ValueError, f.readlines)
+        # "Test mixed iteration and reads."
+        self.createTempFile()
+        linelen = len(self.TEXT_LINES[0])
+        halflen = linelen // 2
+        with bz2.BZ2File(self.filename) as bz2f:
+            bz2f.read(halflen)
+            self.assertEqual(next(bz2f), self.TEXT_LINES[0][halflen:])
+            self.assertEqual(bz2f.read(), self.TEXT[linelen:])
+        with bz2.BZ2File(self.filename) as bz2f:
+            bz2f.readline()
+            self.assertEqual(next(bz2f), self.TEXT_LINES[1])
+            self.assertEqual(bz2f.readline(), self.TEXT_LINES[2])
+        with bz2.BZ2File(self.filename) as bz2f:
+            bz2f.readlines()
+            with self.assertRaises(StopIteration):
+                next(bz2f)
+            self.assertEqual(bz2f.readlines(), [])
+
+    def testReadBytesIO(self):
+        # "Test BZ2File.read() with BytesIO source"
+        with BytesIO(self.getData()) as bio:
+            with BZ2File(fileobj=bio) as bz2f:
+                self.assertRaises(TypeError, bz2f.read, None)
+                self.assertEqual(bz2f.read(), self.TEXT)
+            self.assertFalse(bio.closed)
+
+    def testPeekBytesIO(self):
+        # "Test BZ2File.peek() with BytesIO source"
+        with BytesIO(self.getData()) as bio:
+            with BZ2File(fileobj=bio) as bz2f:
+                pdata = bz2f.peek()
+                self.assertNotEqual(len(pdata), 0)
+                self.assertTrue(self.TEXT.startswith(pdata))
+                self.assertEqual(bz2f.read(), self.TEXT)
+
+    def testWriteBytesIO(self):
+        # "Test BZ2File.write() with BytesIO destination"
+        with BytesIO() as bio:
+            with BZ2File(fileobj=bio, mode="w") as bz2f:
+                self.assertRaises(TypeError, bz2f.write)
+                bz2f.write(self.TEXT)
+            self.assertEqual(self.decompress(bio.getvalue()), self.TEXT)
+            self.assertFalse(bio.closed)
+
+    def testSeekForwardBytesIO(self):
+        # "Test BZ2File.seek(150, 0) with BytesIO source"
+        with BytesIO(self.getData()) as bio:
+            with BZ2File(fileobj=bio) as bz2f:
+                self.assertRaises(TypeError, bz2f.seek)
+                bz2f.seek(150)
+                self.assertEqual(bz2f.read(), self.TEXT[150:])
+
+    def testSeekBackwardsBytesIO(self):
+        # "Test BZ2File.seek(-150, 1) with BytesIO source"
+        with BytesIO(self.getData()) as bio:
+            with BZ2File(fileobj=bio) as bz2f:
+                bz2f.read(500)
+                bz2f.seek(-150, 1)
+                self.assertEqual(bz2f.read(), self.TEXT[500-150:])
 
 class BZ2CompressorTest(BaseTest):
     def testCompress(self):