Mini Shell
# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
SFTP file object
"""
from binascii import hexlify
from collections import deque
import socket
import threading
import time
from paramiko.common import DEBUG, io_sleep
from paramiko.file import BufferedFile
from paramiko.util import u
from paramiko.sftp import (
CMD_CLOSE,
CMD_READ,
CMD_DATA,
SFTPError,
CMD_WRITE,
CMD_STATUS,
CMD_FSTAT,
CMD_ATTRS,
CMD_FSETSTAT,
CMD_EXTENDED,
int64,
)
from paramiko.sftp_attr import SFTPAttributes
class SFTPFile(BufferedFile):
"""
Proxy object for a file on the remote server, in client mode SFTP.
Instances of this class may be used as context managers in the same way
that built-in Python file objects are.
"""
# Some sftp servers will choke if you send read/write requests larger than
# this size.
MAX_REQUEST_SIZE = 32768
def __init__(self, sftp, handle, mode="r", bufsize=-1):
BufferedFile.__init__(self)
self.sftp = sftp
self.handle = handle
BufferedFile._set_mode(self, mode, bufsize)
self.pipelined = False
self._prefetching = False
self._prefetch_done = False
self._prefetch_data = {}
self._prefetch_extents = {}
self._prefetch_lock = threading.Lock()
self._saved_exception = None
self._reqs = deque()
def __del__(self):
self._close(async_=True)
def close(self):
"""
Close the file.
"""
self._close(async_=False)
def _close(self, async_=False):
# We allow double-close without signaling an error, because real
# Python file objects do. However, we must protect against actually
# sending multiple CMD_CLOSE packets, because after we close our
# handle, the same handle may be re-allocated by the server, and we
# may end up mysteriously closing some random other file. (This is
# especially important because we unconditionally call close() from
# __del__.)
if self._closed:
return
self.sftp._log(DEBUG, "close({})".format(u(hexlify(self.handle))))
if self.pipelined:
self.sftp._finish_responses(self)
BufferedFile.close(self)
try:
if async_:
# GC'd file handle could be called from an arbitrary thread
# -- don't wait for a response
self.sftp._async_request(type(None), CMD_CLOSE, self.handle)
else:
self.sftp._request(CMD_CLOSE, self.handle)
except EOFError:
# may have outlived the Transport connection
pass
except (IOError, socket.error):
# may have outlived the Transport connection
pass
def _data_in_prefetch_requests(self, offset, size):
k = [
x for x in list(self._prefetch_extents.values()) if x[0] <= offset
]
if len(k) == 0:
return False
k.sort(key=lambda x: x[0])
buf_offset, buf_size = k[-1]
if buf_offset + buf_size <= offset:
# prefetch request ends before this one begins
return False
if buf_offset + buf_size >= offset + size:
# inclusive
return True
# well, we have part of the request. see if another chunk has
# the rest.
return self._data_in_prefetch_requests(
buf_offset + buf_size, offset + size - buf_offset - buf_size
)
def _data_in_prefetch_buffers(self, offset):
"""
if a block of data is present in the prefetch buffers, at the given
offset, return the offset of the relevant prefetch buffer. otherwise,
return None. this guarantees nothing about the number of bytes
collected in the prefetch buffer so far.
"""
k = [i for i in self._prefetch_data.keys() if i <= offset]
if len(k) == 0:
return None
index = max(k)
buf_offset = offset - index
if buf_offset >= len(self._prefetch_data[index]):
# it's not here
return None
return index
def _read_prefetch(self, size):
"""
read data out of the prefetch buffer, if possible. if the data isn't
in the buffer, return None. otherwise, behaves like a normal read.
"""
# while not closed, and haven't fetched past the current position,
# and haven't reached EOF...
while True:
offset = self._data_in_prefetch_buffers(self._realpos)
if offset is not None:
break
if self._prefetch_done or self._closed:
break
self.sftp._read_response()
self._check_exception()
if offset is None:
self._prefetching = False
return None
prefetch = self._prefetch_data[offset]
del self._prefetch_data[offset]
buf_offset = self._realpos - offset
if buf_offset > 0:
self._prefetch_data[offset] = prefetch[:buf_offset]
prefetch = prefetch[buf_offset:]
if size < len(prefetch):
self._prefetch_data[self._realpos + size] = prefetch[size:]
prefetch = prefetch[:size]
return prefetch
def _read(self, size):
size = min(size, self.MAX_REQUEST_SIZE)
if self._prefetching:
data = self._read_prefetch(size)
if data is not None:
return data
t, msg = self.sftp._request(
CMD_READ, self.handle, int64(self._realpos), int(size)
)
if t != CMD_DATA:
raise SFTPError("Expected data")
return msg.get_string()
def _write(self, data):
# may write less than requested if it would exceed max packet size
chunk = min(len(data), self.MAX_REQUEST_SIZE)
sftp_async_request = self.sftp._async_request(
type(None),
CMD_WRITE,
self.handle,
int64(self._realpos),
data[:chunk],
)
self._reqs.append(sftp_async_request)
if not self.pipelined or (
len(self._reqs) > 100 and self.sftp.sock.recv_ready()
):
while len(self._reqs):
req = self._reqs.popleft()
t, msg = self.sftp._read_response(req)
if t != CMD_STATUS:
raise SFTPError("Expected status")
# convert_status already called
return chunk
def settimeout(self, timeout):
"""
Set a timeout on read/write operations on the underlying socket or
ssh `.Channel`.
:param float timeout:
seconds to wait for a pending read/write operation before raising
``socket.timeout``, or ``None`` for no timeout
.. seealso:: `.Channel.settimeout`
"""
self.sftp.sock.settimeout(timeout)
def gettimeout(self):
"""
Returns the timeout in seconds (as a `float`) associated with the
socket or ssh `.Channel` used for this file.
.. seealso:: `.Channel.gettimeout`
"""
return self.sftp.sock.gettimeout()
def setblocking(self, blocking):
"""
Set blocking or non-blocking mode on the underiying socket or ssh
`.Channel`.
:param int blocking:
0 to set non-blocking mode; non-0 to set blocking mode.
.. seealso:: `.Channel.setblocking`
"""
self.sftp.sock.setblocking(blocking)
def seekable(self):
"""
Check if the file supports random access.
:return:
`True` if the file supports random access. If `False`,
:meth:`seek` will raise an exception
"""
return True
def seek(self, offset, whence=0):
"""
Set the file's current position.
See `file.seek` for details.
"""
self.flush()
if whence == self.SEEK_SET:
self._realpos = self._pos = offset
elif whence == self.SEEK_CUR:
self._pos += offset
self._realpos = self._pos
else:
self._realpos = self._pos = self._get_size() + offset
self._rbuffer = bytes()
def stat(self):
"""
Retrieve information about this file from the remote system. This is
exactly like `.SFTPClient.stat`, except that it operates on an
already-open file.
:returns:
an `.SFTPAttributes` object containing attributes about this file.
"""
t, msg = self.sftp._request(CMD_FSTAT, self.handle)
if t != CMD_ATTRS:
raise SFTPError("Expected attributes")
return SFTPAttributes._from_msg(msg)
def chmod(self, mode):
"""
Change the mode (permissions) of this file. The permissions are
unix-style and identical to those used by Python's `os.chmod`
function.
:param int mode: new permissions
"""
self.sftp._log(
DEBUG, "chmod({}, {!r})".format(hexlify(self.handle), mode)
)
attr = SFTPAttributes()
attr.st_mode = mode
self.sftp._request(CMD_FSETSTAT, self.handle, attr)
def chown(self, uid, gid):
"""
Change the owner (``uid``) and group (``gid``) of this file. As with
Python's `os.chown` function, you must pass both arguments, so if you
only want to change one, use `stat` first to retrieve the current
owner and group.
:param int uid: new owner's uid
:param int gid: new group id
"""
self.sftp._log(
DEBUG,
"chown({}, {!r}, {!r})".format(hexlify(self.handle), uid, gid),
)
attr = SFTPAttributes()
attr.st_uid, attr.st_gid = uid, gid
self.sftp._request(CMD_FSETSTAT, self.handle, attr)
def utime(self, times):
"""
Set the access and modified times of this file. If
``times`` is ``None``, then the file's access and modified times are
set to the current time. Otherwise, ``times`` must be a 2-tuple of
numbers, of the form ``(atime, mtime)``, which is used to set the
access and modified times, respectively. This bizarre API is mimicked
from Python for the sake of consistency -- I apologize.
:param tuple times:
``None`` or a tuple of (access time, modified time) in standard
internet epoch time (seconds since 01 January 1970 GMT)
"""
if times is None:
times = (time.time(), time.time())
self.sftp._log(
DEBUG, "utime({}, {!r})".format(hexlify(self.handle), times)
)
attr = SFTPAttributes()
attr.st_atime, attr.st_mtime = times
self.sftp._request(CMD_FSETSTAT, self.handle, attr)
def truncate(self, size):
"""
Change the size of this file. This usually extends
or shrinks the size of the file, just like the ``truncate()`` method on
Python file objects.
:param size: the new size of the file
"""
self.sftp._log(
DEBUG, "truncate({}, {!r})".format(hexlify(self.handle), size)
)
attr = SFTPAttributes()
attr.st_size = size
self.sftp._request(CMD_FSETSTAT, self.handle, attr)
def check(self, hash_algorithm, offset=0, length=0, block_size=0):
"""
Ask the server for a hash of a section of this file. This can be used
to verify a successful upload or download, or for various rsync-like
operations.
The file is hashed from ``offset``, for ``length`` bytes.
If ``length`` is 0, the remainder of the file is hashed. Thus, if both
``offset`` and ``length`` are zero, the entire file is hashed.
Normally, ``block_size`` will be 0 (the default), and this method will
return a byte string representing the requested hash (for example, a
string of length 16 for MD5, or 20 for SHA-1). If a non-zero
``block_size`` is given, each chunk of the file (from ``offset`` to
``offset + length``) of ``block_size`` bytes is computed as a separate
hash. The hash results are all concatenated and returned as a single
string.
For example, ``check('sha1', 0, 1024, 512)`` will return a string of
length 40. The first 20 bytes will be the SHA-1 of the first 512 bytes
of the file, and the last 20 bytes will be the SHA-1 of the next 512
bytes.
:param str hash_algorithm:
the name of the hash algorithm to use (normally ``"sha1"`` or
``"md5"``)
:param offset:
offset into the file to begin hashing (0 means to start from the
beginning)
:param length:
number of bytes to hash (0 means continue to the end of the file)
:param int block_size:
number of bytes to hash per result (must not be less than 256; 0
means to compute only one hash of the entire segment)
:return:
`str` of bytes representing the hash of each block, concatenated
together
:raises:
``IOError`` -- if the server doesn't support the "check-file"
extension, or possibly doesn't support the hash algorithm requested
.. note:: Many (most?) servers don't support this extension yet.
.. versionadded:: 1.4
"""
t, msg = self.sftp._request(
CMD_EXTENDED,
"check-file",
self.handle,
hash_algorithm,
int64(offset),
int64(length),
block_size,
)
msg.get_text() # ext
msg.get_text() # alg
data = msg.get_remainder()
return data
def set_pipelined(self, pipelined=True):
"""
Turn on/off the pipelining of write operations to this file. When
pipelining is on, paramiko won't wait for the server response after
each write operation. Instead, they're collected as they come in. At
the first non-write operation (including `.close`), all remaining
server responses are collected. This means that if there was an error
with one of your later writes, an exception might be thrown from within
`.close` instead of `.write`.
By default, files are not pipelined.
:param bool pipelined:
``True`` if pipelining should be turned on for this file; ``False``
otherwise
.. versionadded:: 1.5
"""
self.pipelined = pipelined
def prefetch(self, file_size=None, max_concurrent_requests=None):
"""
Pre-fetch the remaining contents of this file in anticipation of future
`.read` calls. If reading the entire file, pre-fetching can
dramatically improve the download speed by avoiding roundtrip latency.
The file's contents are incrementally buffered in a background thread.
The prefetched data is stored in a buffer until read via the `.read`
method. Once data has been read, it's removed from the buffer. The
data may be read in a random order (using `.seek`); chunks of the
buffer that haven't been read will continue to be buffered.
:param int file_size:
When this is ``None`` (the default), this method calls `stat` to
determine the remote file size. In some situations, doing so can
cause exceptions or hangs (see `#562
<https://github.com/paramiko/paramiko/pull/562>`_); as a
workaround, one may call `stat` explicitly and pass its value in
via this parameter.
:param int max_concurrent_requests:
The maximum number of concurrent read requests to prefetch. See
`.SFTPClient.get` (its ``max_concurrent_prefetch_requests`` param)
for details.
.. versionadded:: 1.5.1
.. versionchanged:: 1.16.0
The ``file_size`` parameter was added (with no default value).
.. versionchanged:: 1.16.1
The ``file_size`` parameter was made optional for backwards
compatibility.
.. versionchanged:: 3.3
Added ``max_concurrent_requests``.
"""
if file_size is None:
file_size = self.stat().st_size
# queue up async reads for the rest of the file
chunks = []
n = self._realpos
while n < file_size:
chunk = min(self.MAX_REQUEST_SIZE, file_size - n)
chunks.append((n, chunk))
n += chunk
if len(chunks) > 0:
self._start_prefetch(chunks, max_concurrent_requests)
def readv(self, chunks, max_concurrent_prefetch_requests=None):
"""
Read a set of blocks from the file by (offset, length). This is more
efficient than doing a series of `.seek` and `.read` calls, since the
prefetch machinery is used to retrieve all the requested blocks at
once.
:param chunks:
a list of ``(offset, length)`` tuples indicating which sections of
the file to read
:param int max_concurrent_prefetch_requests:
The maximum number of concurrent read requests to prefetch. See
`.SFTPClient.get` (its ``max_concurrent_prefetch_requests`` param)
for details.
:return: a list of blocks read, in the same order as in ``chunks``
.. versionadded:: 1.5.4
.. versionchanged:: 3.3
Added ``max_concurrent_prefetch_requests``.
"""
self.sftp._log(
DEBUG, "readv({}, {!r})".format(hexlify(self.handle), chunks)
)
read_chunks = []
for offset, size in chunks:
# don't fetch data that's already in the prefetch buffer
if self._data_in_prefetch_buffers(
offset
) or self._data_in_prefetch_requests(offset, size):
continue
# break up anything larger than the max read size
while size > 0:
chunk_size = min(size, self.MAX_REQUEST_SIZE)
read_chunks.append((offset, chunk_size))
offset += chunk_size
size -= chunk_size
self._start_prefetch(read_chunks, max_concurrent_prefetch_requests)
# now we can just devolve to a bunch of read()s :)
for x in chunks:
self.seek(x[0])
yield self.read(x[1])
# ...internals...
def _get_size(self):
try:
return self.stat().st_size
except:
return 0
def _start_prefetch(self, chunks, max_concurrent_requests=None):
self._prefetching = True
self._prefetch_done = False
t = threading.Thread(
target=self._prefetch_thread,
args=(chunks, max_concurrent_requests),
)
t.daemon = True
t.start()
def _prefetch_thread(self, chunks, max_concurrent_requests):
# do these read requests in a temporary thread because there may be
# a lot of them, so it may block.
for offset, length in chunks:
# Limit the number of concurrent requests in a busy-loop
if max_concurrent_requests is not None:
while True:
with self._prefetch_lock:
pf_len = len(self._prefetch_extents)
if pf_len < max_concurrent_requests:
break
time.sleep(io_sleep)
num = self.sftp._async_request(
self, CMD_READ, self.handle, int64(offset), int(length)
)
with self._prefetch_lock:
self._prefetch_extents[num] = (offset, length)
def _async_response(self, t, msg, num):
if t == CMD_STATUS:
# save exception and re-raise it on next file operation
try:
self.sftp._convert_status(msg)
except Exception as e:
self._saved_exception = e
return
if t != CMD_DATA:
raise SFTPError("Expected data")
data = msg.get_string()
while True:
with self._prefetch_lock:
# spin if in race with _prefetch_thread
if num in self._prefetch_extents:
offset, length = self._prefetch_extents[num]
self._prefetch_data[offset] = data
del self._prefetch_extents[num]
if len(self._prefetch_extents) == 0:
self._prefetch_done = True
break
def _check_exception(self):
"""if there's a saved exception, raise & clear it"""
if self._saved_exception is not None:
x = self._saved_exception
self._saved_exception = None
raise x
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