# 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 distrubuted 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.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
"""
BufferedFile.
"""
from cStringIO import StringIO
class BufferedFile (object):
"""
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 = StringIO()
self._rbuffer = ''
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.
@raise ValueError: if the file is closed.
@return: an interator.
@rtype: iterator
"""
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 = StringIO()
return
def next(self):
"""
Returns the next line from the input, or raises L{StopIteration} when
EOF is hit. Unlike python file objects, it's okay to mix calls to
C{next} and L{readline}.
@raise StopIteration: when the end of the file is reached.
@return: a line read from the file.
@rtype: str
"""
line = self.readline()
if not line:
raise StopIteration
return line
def read(self, size=None):
"""
Read at most C{size} bytes from the file (less if we hit the end of the
file first). If the C{size} argument is negative or omitted, read all
the remaining data in the file.
@param size: maximum number of bytes to read
@type size: int
@return: data read from the file, or an empty string if EOF was
encountered immediately
@rtype: str
"""
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 = self._rbuffer
self._rbuffer = ''
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 += new_data
self._realpos += len(new_data)
self._pos += len(new_data)
return 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 C{fgets()}, the returned string contains null
characters (C{'\\0'}) if they occurred in the input.
@param size: maximum length of returned string.
@type size: int
@return: next line of the file, or an empty string if the end of the
file has been reached.
@rtype: str
"""
# 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
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] == '\n':
line = line[1:]
self._record_newline('\r\n')
else:
self._record_newline('\r')
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 and return
self._rbuffer = line[size:]
line = line[:size]
self._pos += len(line)
return line
n = size - len(line)
else:
n = self._bufsize
if ('\n' in line) or ((self._flags & self.FLAG_UNIVERSAL_NEWLINE) and ('\r' 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 = ''
self._pos += len(line)
return line
line += new_data
self._realpos += len(new_data)
# find the newline
pos = line.find('\n')
if self._flags & self.FLAG_UNIVERSAL_NEWLINE:
rpos = line.find('\r')
if (rpos >= 0) and ((rpos < pos) or (pos < 0)):
pos = rpos
xpos = pos + 1
if (line[pos] == '\r') and (xpos < len(line)) and (line[xpos] == '\n'):
xpos += 1
self._rbuffer = line[xpos:]
lf = line[pos:xpos]
line = line[:pos] + '\n'
if (len(self._rbuffer) == 0) and (lf == '\r'):
# 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
def readlines(self, sizehint=None):
"""
Read all remaining lines using L{readline} and return them as a list.
If the optional C{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 sizehint: desired maximum number of bytes to read.
@type sizehint: int
@return: list of lines read from the file.
@rtype: list
"""
lines = []
bytes = 0
while True:
line = self.readline()
if len(line) == 0:
break
lines.append(line)
bytes += len(line)
if (sizehint is not None) and (bytes >= sizehint):
break
return lines
def seek(self, offset, whence=0):
"""
Set the file's current position, like stdio's C{fseek}. Not all file
objects support seeking.
@note: If a file is opened in append mode (C{'a'} or C{'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 offset: position to move to within the file, relative to
C{whence}.
@type offset: int
@param whence: type of movement: 0 = absolute; 1 = relative to the
current position; 2 = relative to the end of the file.
@type whence: int
@raise 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.
@return: file position (in bytes).
@rtype: int
"""
return self._pos
def write(self, data):
"""
Write data to the file. If write buffering is on (C{bufsize} was
specified and non-zero), some or all of the data may not actually be
written yet. (Use L{flush} or L{close} to force buffered data to be
written out.)
@param data: data to write.
@type data: str
"""
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('\n')
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 = StringIO()
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 L{readlines}; C{writelines} does not add line
separators.)
@param sequence: an iterable sequence of strings.
@type sequence: sequence
"""
for line in sequence:
self.write(line)
return
def xreadlines(self):
"""
Identical to C{iter(f)}. This is a deprecated file interface that
predates python iterator support.
@return: an iterator.
@rtype: iterator
"""
return self
### overrides...
def _read(self, size):
"""
I{(subclass override)}
Read data from the stream. Return C{None} or raise C{EOFError} to
indicate EOF.
"""
raise EOFError()
def _write(self, data):
"""
I{(subclass override)}
Write data into the stream.
"""
raise IOError('write not implemented')
def _get_size(self):
"""
I{(subclass override)}
Return the size of the file. This is called from within L{_set_mode}
if the file is opened in append mode, so the file position can be
tracked and L{seek} and L{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, data):
# the underlying stream may be something that does partial writes (like
# a socket).
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 (type(self.newlines) is str) and (self.newlines != newline):
self.newlines = (self.newlines, newline)
elif newline not in self.newlines:
self.newlines += (newline,)