def _probe_seek_hole(self):
"""
Check whether the system implements 'SEEK_HOLE' and 'SEEK_DATA'.
Unfortunately, there seems to be no clean way for detecting this,
because often the system just fakes them by just assuming that all
files are fully mapped, so 'SEEK_HOLE' always returns EOF and
'SEEK_DATA' always returns the requested offset.
I could not invent a better way of detecting the fake 'SEEK_HOLE'
implementation than just to create a temporary file in the same
directory where the image file resides. It would be nice to change this
to something better.
"""
directory = os.path.dirname(self._image_path)
try:
tmp_obj = tempfile.TemporaryFile("w+", dir=directory)
except IOError as err:
raise ErrorNotSupp("cannot create a temporary in \"%s\": %s"
% (directory, err))
try:
os.ftruncate(tmp_obj.fileno(), self.block_size)
except OSError as err:
raise ErrorNotSupp("cannot truncate temporary file in \"%s\": %s"
% (directory, err))
offs = _lseek(tmp_obj, 0, _SEEK_HOLE)
if offs != 0:
# We are dealing with the stub 'SEEK_HOLE' implementation which
# always returns EOF.
self._log.debug("lseek(0, SEEK_HOLE) returned %d" % offs)
raise ErrorNotSupp("the file-system does not support "
"\"SEEK_HOLE\" and \"SEEK_DATA\" but only "
"provides a stub implementation")
tmp_obj.close()
python类lseek()的实例源码
def test_read(self):
with open(support.TESTFN, "w+b") as fobj:
fobj.write(b"spam")
fobj.flush()
fd = fobj.fileno()
os.lseek(fd, 0, 0)
s = os.read(fd, 4)
self.assertEqual(type(s), bytes)
self.assertEqual(s, b"spam")
def test_lseek(self):
if hasattr(os, "lseek"):
self.check(os.lseek, 0, 0)
def test_stdin_filedes(self):
# stdin is set to open file descriptor
tf = tempfile.TemporaryFile()
self.addCleanup(tf.close)
d = tf.fileno()
os.write(d, b"pear")
os.lseek(d, 0, 0)
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.exit(sys.stdin.read() == "pear")'],
stdin=d)
p.wait()
self.assertEqual(p.returncode, 1)
def test_stdout_filedes(self):
# stdout is set to open file descriptor
tf = tempfile.TemporaryFile()
self.addCleanup(tf.close)
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stdout.write("orange")'],
stdout=d)
p.wait()
os.lseek(d, 0, 0)
self.assertEqual(os.read(d, 1024), b"orange")
def test_stderr_filedes(self):
# stderr is set to open file descriptor
tf = tempfile.TemporaryFile()
self.addCleanup(tf.close)
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stderr.write("strawberry")'],
stderr=d)
p.wait()
os.lseek(d, 0, 0)
self.assertStderrEqual(os.read(d, 1024), b"strawberry")
def test_textmode(self):
# _mkstemp_inner can create files in text mode
if not has_textmode:
return # ugh, can't use SkipTest.
# A text file is truncated at the first Ctrl+Z byte
f = self.do_create(bin=0)
f.write(b"blat\x1a")
f.write(b"extra\n")
os.lseek(f.fd, 0, os.SEEK_SET)
self.assertEqual(os.read(f.fd, 20), b"blat")
def test_lseek(self):
if verbose:
print('play around with os.lseek() with the built largefile')
with self.open(TESTFN, 'rb') as f:
self.assertEqual(os.lseek(f.fileno(), 0, 0), 0)
self.assertEqual(os.lseek(f.fileno(), 42, 0), 42)
self.assertEqual(os.lseek(f.fileno(), 42, 1), 84)
self.assertEqual(os.lseek(f.fileno(), 0, 1), 84)
self.assertEqual(os.lseek(f.fileno(), 0, 2), size+1+0)
self.assertEqual(os.lseek(f.fileno(), -10, 2), size+1-10)
self.assertEqual(os.lseek(f.fileno(), -size-1, 2), 0)
self.assertEqual(os.lseek(f.fileno(), size, 0), size)
# the 'a' that was written at the end of file above
self.assertEqual(f.read(1), b'a')
def _write(self, piece):
pos = piece.index * self.torrent.info.piece_length
os.lseek(self.fd, pos, os.SEEK_SET)
os.write(self.fd, piece.data)
def read(self, begin, index, length):
pos = index * self.torrent.info.piece_length
os.lseek(self.fd, pos, os.SEEK_SET)
return os.read(self.fd, length)
def test_lseek(self):
self.check(os.lseek, 0, 0)
def test_stdin_filedes(self):
# stdin is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
os.write(d, "pear")
os.lseek(d, 0, 0)
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.exit(sys.stdin.read() == "pear")'],
stdin=d)
p.wait()
self.assertEqual(p.returncode, 1)
def test_stdout_filedes(self):
# stdout is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stdout.write("orange")'],
stdout=d)
p.wait()
os.lseek(d, 0, 0)
self.assertEqual(os.read(d, 1024), "orange")
def test_stderr_filedes(self):
# stderr is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stderr.write("strawberry")'],
stderr=d)
p.wait()
os.lseek(d, 0, 0)
self.assertStderrEqual(os.read(d, 1024), "strawberry")
def test_lseek(self):
self.check(os.lseek, 0, 0)
def test_stdin_filedes(self):
# stdin is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
os.write(d, "pear")
os.lseek(d, 0, 0)
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.exit(sys.stdin.read() == "pear")'],
stdin=d)
p.wait()
self.assertEqual(p.returncode, 1)
def test_stdout_filedes(self):
# stdout is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stdout.write("orange")'],
stdout=d)
p.wait()
os.lseek(d, 0, 0)
self.assertEqual(os.read(d, 1024), "orange")
def test_stderr_filedes(self):
# stderr is set to open file descriptor
tf = tempfile.TemporaryFile()
d = tf.fileno()
p = subprocess.Popen([sys.executable, "-c",
'import sys; sys.stderr.write("strawberry")'],
stderr=d)
p.wait()
os.lseek(d, 0, 0)
self.assertStderrEqual(os.read(d, 1024), "strawberry")
def __init__(self, buf = None, pos = 0, filename = None, fp = None):
if fp is not None:
try:
fileno = fp.fileno()
length = os.path.getsize(fp.name)
import mmap
except:
# read whole file into memory
buf = fp.read()
pos = 0
else:
# map the whole file into memory
if length:
# length must not be zero
buf = mmap.mmap(fileno, length, access = mmap.ACCESS_READ)
pos = os.lseek(fileno, 0, 1)
else:
buf = ''
pos = 0
if filename is None:
try:
filename = fp.name
except AttributeError:
filename = None
self.buf = buf
self.pos = pos
self.line = 1
self.col = 1
self.filename = filename
def _save_chunk(self, n, data):
if self._part_fd < 0:
if not self._open_files():
return False
assert self._part_fd >= 0
offs = self.chunk_size * n
os.lseek(self._part_fd, offs, os.SEEK_SET)
os.write(self._part_fd, data)
self._segments_file.write(self._segments)
return True
