# Copyright (C) 2003-2007 Robey Pointer <[email protected]>
#
# 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.
from io import BytesIO
from paramiko.common import (
linefeed_byte_value,
crlf,
cr_byte,
linefeed_byte,
cr_byte_value,
)
from paramiko.util import ClosingContextManager, u
class BufferedFile(ClosingContextManager):
"""
Reusable base class to implement Python-style file buffering around a
simpler stream.
"""
_DEFAULT_BUFSIZE = 8192
SEEK_SET = 0
SEEK_CUR = 1
SEEK_END = 2
FLAG_READ = 0x1
FLAG_WRITE = 0x2
FLAG_APPEND = 0x4
FLAG_BINARY = 0x10
FLAG_BUFFERED = 0x20
FLAG_LINE_BUFFERED = 0x40
FLAG_UNIVERSAL_NEWLINE = 0x80
def __init__(self):
self.newlines = None
self._flags = 0
self._bufsize = self._DEFAULT_BUFSIZE
self._wbuffer = BytesIO()
self._rbuffer = bytes()
self._at_trailing_cr = False
self._closed = False
# pos - position within the file, according to the user
# realpos - position according the OS
# (these may be different because we buffer for line reading)
self._pos = self._realpos = 0
# size only matters for seekable files
self._size = 0
def __del__(self):
self.close()
def __iter__(self):
"""
Returns an iterator that can be used to iterate over the lines in this
file. This iterator happens to return the file itself, since a file is
its own iterator.
:raises: ``ValueError`` -- if the file is closed.
"""
if self._closed:
raise ValueError("I/O operation on closed file")
return self
def close(self):
"""
Close the file. Future read and write operations will fail.
"""
self.flush()
self._closed = True
def flush(self):
"""
Write out any data in the write buffer. This may do nothing if write
buffering is not turned on.
"""
self._write_all(self._wbuffer.getvalue())
self._wbuffer = BytesIO()
return
def __next__(self):
"""
Returns the next line from the input, or raises ``StopIteration``
when EOF is hit. Unlike python file objects, it's okay to mix
calls to `.next` and `.readline`.
:raises: ``StopIteration`` -- when the end of the file is reached.
:returns:
a line (`str`, or `bytes` if the file was opened in binary mode)
read from the file.
"""
line = self.readline()
if not line:
raise StopIteration
return line
def readable(self):
"""
Check if the file can be read from.
:returns:
`True` if the file can be read from. If `False`, `read` will raise
an exception.
"""
return (self._flags & self.FLAG_READ) == self.FLAG_READ
def writable(self):
"""
Check if the file can be written to.
:returns:
`True` if the file can be written to. If `False`, `write` will
raise an exception.
"""
return (self._flags & self.FLAG_WRITE) == self.FLAG_WRITE
def seekable(self):
"""
Check if the file supports random access.
:returns:
`True` if the file supports random access. If `False`, `seek` will
raise an exception.
"""
return False
def readinto(self, buff):
"""
Read up to ``len(buff)`` bytes into ``bytearray`` *buff* and return the
number of bytes read.
:returns:
The number of bytes read.
"""
data = self.read(len(buff))
buff[: len(data)] = data
return len(data)
def read(self, size=None):
"""
Read at most ``size`` bytes from the file (less if we hit the end of
the file first). If the ``size`` argument is negative or omitted,
read all the remaining data in the file.
.. note::
``'b'`` mode flag is ignored (``self.FLAG_BINARY`` in
``self._flags``), because SSH treats all files as binary, since we
have no idea what encoding the file is in, or even if the file is
text data.
:param int size: maximum number of bytes to read
:returns:
data read from the file (as bytes), or an empty string if EOF was
encountered immediately
"""
if self._closed:
raise IOError("File is closed")
if not (self._flags & self.FLAG_READ):
raise IOError("File is not open for reading")
if (size is None) or (size < 0):
# go for broke
result = bytearray(self._rbuffer)
self._rbuffer = bytes()
self._pos += len(result)
while True:
try:
new_data = self._read(self._DEFAULT_BUFSIZE)
except EOFError:
new_data = None
if (new_data is None) or (len(new_data) == 0):
break
result.extend(new_data)
self._realpos += len(new_data)
self._pos += len(new_data)
return bytes(result)
if size <= len(self._rbuffer):
result = self._rbuffer[:size]
self._rbuffer = self._rbuffer[size:]
self._pos += len(result)
return result
while len(self._rbuffer) < size:
read_size = size - len(self._rbuffer)
if self._flags & self.FLAG_BUFFERED:
read_size = max(self._bufsize, read_size)
try:
new_data = self._read(read_size)
except EOFError:
new_data = None
if (new_data is None) or (len(new_data) == 0):
break
self._rbuffer += new_data
self._realpos += len(new_data)
result = self._rbuffer[:size]
self._rbuffer = self._rbuffer[size:]
self._pos += len(result)
return result
def readline(self, size=None):
"""
Read one entire line from the file. A trailing newline character is
kept in the string (but may be absent when a file ends with an
incomplete line). If the size argument is present and non-negative, it
is a maximum byte count (including the trailing newline) and an
incomplete line may be returned. An empty string is returned only when
EOF is encountered immediately.
.. note::
Unlike stdio's ``fgets``, the returned string contains null
characters (``'\\0'``) if they occurred in the input.
:param int size: maximum length of returned string.
:returns:
next line of the file, or an empty string if the end of the
file has been reached.
If the file was opened in binary (``'b'``) mode: bytes are returned
Else: the encoding of the file is assumed to be UTF-8 and character
strings (`str`) are returned
"""
# it's almost silly how complex this function is.
if self._closed:
raise IOError("File is closed")
if not (self._flags & self.FLAG_READ):
raise IOError("File not open for reading")
line = self._rbuffer
truncated = False
while True:
if (
self._at_trailing_cr
and self._flags & self.FLAG_UNIVERSAL_NEWLINE
and len(line) > 0
):
# edge case: the newline may be '\r\n' and we may have read
# only the first '\r' last time.
if line[0] == linefeed_byte_value:
line = line[1:]
self._record_newline(crlf)
else:
self._record_newline(cr_byte)
self._at_trailing_cr = False
# check size before looking for a linefeed, in case we already have
# enough.
if (size is not None) and (size >= 0):
if len(line) >= size:
# truncate line
self._rbuffer = line[size:]
line = line[:size]
truncated = True
break
n = size - len(line)
else:
n = self._bufsize
if linefeed_byte in line or (
self._flags & self.FLAG_UNIVERSAL_NEWLINE and cr_byte in line
):
break
try:
new_data = self._read(n)
except EOFError:
new_data = None
if (new_data is None) or (len(new_data) == 0):
self._rbuffer = bytes()
self._pos += len(line)
return line if self._flags & self.FLAG_BINARY else u(line)
line += new_data
self._realpos += len(new_data)
# find the newline
pos = line.find(linefeed_byte)
if self._flags & self.FLAG_UNIVERSAL_NEWLINE:
rpos = line.find(cr_byte)
if (rpos >= 0) and (rpos < pos or pos < 0):
pos = rpos
if pos == -1:
# we couldn't find a newline in the truncated string, return it
self._pos += len(line)
return line if self._flags & self.FLAG_BINARY else u(line)
xpos = pos + 1
if (
line[pos] == cr_byte_value
and xpos < len(line)
and line[xpos] == linefeed_byte_value
):
xpos += 1
# if the string was truncated, _rbuffer needs to have the string after
# the newline character plus the truncated part of the line we stored
# earlier in _rbuffer
if truncated:
self._rbuffer = line[xpos:] + self._rbuffer
else:
self._rbuffer = line[xpos:]
lf = line[pos:xpos]
line = line[:pos] + linefeed_byte
if (len(self._rbuffer) == 0) and (lf == cr_byte):
# we could read the line up to a '\r' and there could still be a
# '\n' following that we read next time. note that and eat it.
self._at_trailing_cr = True
else:
self._record_newline(lf)
self._pos += len(line)
return line if self._flags & self.FLAG_BINARY else u(line)
def readlines(self, sizehint=None):
"""
Read all remaining lines using `readline` and return them as a list.
If the optional ``sizehint`` argument is present, instead of reading up
to EOF, whole lines totalling approximately sizehint bytes (possibly
after rounding up to an internal buffer size) are read.
:param int sizehint: desired maximum number of bytes to read.
:returns: list of lines read from the file.
"""
lines = []
byte_count = 0
while True:
line = self.readline()
if len(line) == 0:
break
lines.append(line)
byte_count += len(line)
if (sizehint is not None) and (byte_count >= sizehint):
break
return lines
def seek(self, offset, whence=0):
"""
Set the file's current position, like stdio's ``fseek``. Not all file
objects support seeking.
.. note::
If a file is opened in append mode (``'a'`` or ``'a+'``), any seek
operations will be undone at the next write (as the file position
will move back to the end of the file).
:param int offset:
position to move to within the file, relative to ``whence``.
:param int whence:
type of movement: 0 = absolute; 1 = relative to the current
position; 2 = relative to the end of the file.
:raises: ``IOError`` -- if the file doesn't support random access.
"""
raise IOError("File does not support seeking.")
def tell(self):
"""
Return the file's current position. This may not be accurate or
useful if the underlying file doesn't support random access, or was
opened in append mode.
:returns: file position (`number <int>` of bytes).
"""
return self._pos
def write(self, data):
"""
Write data to the file. If write buffering is on (``bufsize`` was
specified and non-zero), some or all of the data may not actually be
written yet. (Use `flush` or `close` to force buffered data to be
written out.)
:param data: ``str``/``bytes`` data to write
"""
if isinstance(data, str):
# Accept text and encode as utf-8 for compatibility only.
data = data.encode("utf-8")
if self._closed:
raise IOError("File is closed")
if not (self._flags & self.FLAG_WRITE):
raise IOError("File not open for writing")
if not (self._flags & self.FLAG_BUFFERED):
self._write_all(data)
return
self._wbuffer.write(data)
if self._flags & self.FLAG_LINE_BUFFERED:
# only scan the new data for linefeed, to avoid wasting time.
last_newline_pos = data.rfind(linefeed_byte)
if last_newline_pos >= 0:
wbuf = self._wbuffer.getvalue()
last_newline_pos += len(wbuf) - len(data)
self._write_all(wbuf[: last_newline_pos + 1])
self._wbuffer = BytesIO()
self._wbuffer.write(wbuf[last_newline_pos + 1 :])
return
# even if we're line buffering, if the buffer has grown past the
# buffer size, force a flush.
if self._wbuffer.tell() >= self._bufsize:
self.flush()
return
def writelines(self, sequence):
"""
Write a sequence of strings to the file. The sequence can be any
iterable object producing strings, typically a list of strings. (The
name is intended to match `readlines`; `writelines` does not add line
separators.)
:param sequence: an iterable sequence of strings.
"""
for line in sequence:
self.write(line)
return
def xreadlines(self):
"""
Identical to ``iter(f)``. This is a deprecated file interface that
predates Python iterator support.
"""
return self
@property
def closed(self):
return self._closed
# ...overrides...
def _read(self, size):
"""
(subclass override)
Read data from the stream. Return ``None`` or raise ``EOFError`` to
indicate EOF.
"""
raise EOFError()
def _write(self, data):
"""
(subclass override)
Write data into the stream.
"""
raise IOError("write not implemented")
def _get_size(self):
"""
(subclass override)
Return the size of the file. This is called from within `_set_mode`
if the file is opened in append mode, so the file position can be
tracked and `seek` and `tell` will work correctly. If the file is
a stream that can't be randomly accessed, you don't need to override
this method,
"""
return 0
# ...internals...
def _set_mode(self, mode="r", bufsize=-1):
"""
Subclasses call this method to initialize the BufferedFile.
"""
# set bufsize in any event, because it's used for readline().
self._bufsize = self._DEFAULT_BUFSIZE
if bufsize < 0:
# do no buffering by default, because otherwise writes will get
# buffered in a way that will probably confuse people.
bufsize = 0
if bufsize == 1:
# apparently, line buffering only affects writes. reads are only
# buffered if you call readline (directly or indirectly: iterating
# over a file will indirectly call readline).
self._flags |= self.FLAG_BUFFERED | self.FLAG_LINE_BUFFERED
elif bufsize > 1:
self._bufsize = bufsize
self._flags |= self.FLAG_BUFFERED
self._flags &= ~self.FLAG_LINE_BUFFERED
elif bufsize == 0:
# unbuffered
self._flags &= ~(self.FLAG_BUFFERED | self.FLAG_LINE_BUFFERED)
if ("r" in mode) or ("+" in mode):
self._flags |= self.FLAG_READ
if ("w" in mode) or ("+" in mode):
self._flags |= self.FLAG_WRITE
if "a" in mode:
self._flags |= self.FLAG_WRITE | self.FLAG_APPEND
self._size = self._get_size()
self._pos = self._realpos = self._size
if "b" in mode:
self._flags |= self.FLAG_BINARY
if "U" in mode:
self._flags |= self.FLAG_UNIVERSAL_NEWLINE
# built-in file objects have this attribute to store which kinds of
# line terminations they've seen:
# <http://www.python.org/doc/current/lib/built-in-funcs.html>
self.newlines = None
def _write_all(self, raw_data):
# the underlying stream may be something that does partial writes (like
# a socket).
data = memoryview(raw_data)
while len(data) > 0:
count = self._write(data)
data = data[count:]
if self._flags & self.FLAG_APPEND:
self._size += count
self._pos = self._realpos = self._size
else:
self._pos += count
self._realpos += count
return None
def _record_newline(self, newline):
# silliness about tracking what kinds of newlines we've seen.
# i don't understand why it can be None, a string, or a tuple, instead
# of just always being a tuple, but we'll emulate that behavior anyway.
if not (self._flags & self.FLAG_UNIVERSAL_NEWLINE):
return
if self.newlines is None:
self.newlines = newline
elif self.newlines != newline and isinstance(self.newlines, bytes):
self.newlines = (self.newlines, newline)
elif newline not in self.newlines:
self.newlines += (newline,)