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# Copyright 2002 Ben Escoto
#
# This file is part of rdiff-backup.
#
# rdiff-backup is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA
# 02139, USA; either version 2 of the License, or (at your option) any
# later version; incorporated herein by reference.
"""Convert an iterator to a file object and vice-versa"""
import cPickle, array
import Globals, C
class IterFileException(Exception): pass
class UnwrapFile:
"""Contains some basic methods for parsing a file containing an iter"""
def __init__(self, file):
self.file = file
def _s2l_old(self, s):
"""Convert string to long int"""
assert len(s) == 7
l = 0L
for i in range(7): l = l*256 + ord(s[i])
return l
def _get(self):
"""Return pair (type, data) next in line on the file
type is a single character which is either "o" for object, "f"
for file, "c" for a continution of a file, or None if no more
data can be read. Data is either the file's data, if type is
"c" or "f", or the actual object if the type is "o".
"""
header = self.file.read(8)
if not header: return None, None
if len(header) != 8:
assert None, "Header %s is only %d bytes" % (header, len(header))
type, length = header[0], C.str2long(header[1:])
buf = self.file.read(length)
if type == "o": return type, cPickle.loads(buf)
else: return type, buf
class IterWrappingFile(UnwrapFile):
"""An iterator generated from a file.
Initialize with a file type object, and then it will return the
elements of the file in order.
"""
def __init__(self, file):
UnwrapFile.__init__(self, file)
self.currently_in_file = None
def __iter__(self): return self
def next(self):
if self.currently_in_file:
self.currently_in_file.close() # no error checking by this point
type, data = self._get()
if not type: raise StopIteration
if type == "o": return data
elif type == "f":
file = IterVirtualFile(self, data)
if data: self.currently_in_file = file
else: self.currently_in_file = None
return file
else: raise IterFileException("Bad file type %s" % type)
class IterVirtualFile(UnwrapFile):
"""Another version of a pretend file
This is returned by IterWrappingFile when a file is embedded in
the main file that the IterWrappingFile is based around.
"""
def __init__(self, iwf, initial_data):
"""Initializer
initial_data is the data from the first block of the file.
iwf is the iter wrapping file that spawned this
IterVirtualFile.
"""
UnwrapFile.__init__(self, iwf.file)
self.iwf = iwf
self.buffer = initial_data
self.closed = None
def read(self, length):
"""Read length bytes from the file, updating buffers as necessary"""
assert not self.closed
if self.iwf.currently_in_file:
while length >= len(self.buffer):
if not self.addtobuffer(): break
real_len = min(length, len(self.buffer))
return_val = self.buffer[:real_len]
self.buffer = self.buffer[real_len:]
return return_val
def addtobuffer(self):
"""Read a chunk from the file and add it to the buffer"""
assert self.iwf.currently_in_file
type, data = self._get()
assert type == "c", "Type is %s instead of c" % type
if data:
self.buffer += data
return 1
else:
self.iwf.currently_in_file = None
return None
def close(self):
"""Currently just reads whats left and discards it"""
while self.iwf.currently_in_file:
self.addtobuffer()
self.buffer = ""
self.closed = 1
class FileWrappingIter:
"""A file interface wrapping around an iterator
This is initialized with an iterator, and then converts it into a
stream of characters. The object will evaluate as little of the
iterator as is necessary to provide the requested bytes.
The actual file is a sequence of marshaled objects, each preceded
by 8 bytes which identifies the following the type of object, and
specifies its length. File objects are not marshalled, but the
data is written in chunks of Globals.blocksize, and the following
blocks can identify themselves as continuations.
"""
def __init__(self, iter):
"""Initialize with iter"""
self.iter = iter
self.array_buf = array.array('c')
self.currently_in_file = None
self.closed = None
def read(self, length):
"""Return next length bytes in file"""
assert not self.closed
while len(self.array_buf) < length:
if not self.addtobuffer(): break
result = self.array_buf[:length].tostring()
del self.array_buf[:length]
return result
def addtobuffer(self):
"""Updates self.buffer, adding a chunk from the iterator.
Returns None if we have reached the end of the iterator,
otherwise return true.
"""
array_buf = self.array_buf
if self.currently_in_file:
array_buf.fromstring("c")
array_buf.fromstring(self.addfromfile())
else:
try: currentobj = self.iter.next()
except StopIteration: return None
if hasattr(currentobj, "read") and hasattr(currentobj, "close"):
self.currently_in_file = currentobj
array_buf.fromstring("f")
array_buf.fromstring(self.addfromfile())
else:
pickle = cPickle.dumps(currentobj, 1)
array_buf.fromstring("o")
array_buf.fromstring(C.long2str(long(len(pickle))))
array_buf.fromstring(pickle)
return 1
def addfromfile(self):
"""Read a chunk from the current file and return it"""
buf = self.currently_in_file.read(Globals.blocksize)
if not buf:
assert not self.currently_in_file.close()
self.currently_in_file = None
return C.long2str(long(len(buf))) + buf
def _l2s_old(self, l):
"""Convert long int to string of 7 characters"""
s = ""
for i in range(7):
l, remainder = divmod(l, 256)
s = chr(remainder) + s
assert remainder == 0
return s
def close(self): self.closed = 1
class BufferedRead:
"""Buffer the .read() calls to the given file
This is used to lessen overhead and latency when a file is sent
over a connection. Profiling said that arrays were faster than
strings here.
"""
def __init__(self, file):
self.file = file
self.array_buf = array.array('c')
self.bufsize = Globals.conn_bufsize
def read(self, l = -1):
array_buf = self.array_buf
if l < 0: # Read as much as possible
result = array_buf.tostring() + self.file.read()
del array_buf[:]
return result
if len(array_buf) < l: # Try to make buffer at least as long as l
array_buf.fromstring(self.file.read(max(self.bufsize, l)))
result = array_buf[:l].tostring()
del array_buf[:l]
return result
def close(self): return self.file.close()
from log import *
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