Opening and Saving Files made easier.
I got tired of rewriting the open/save logic on every application, so I turned it into a module.
It's your old tired open/save stuff,w ith a few twists. For starters, since the app I was doing it for (Notty) creates large files, I added compression (Sadly, I couldn't make it gzip-compatible).
And since some files for that app could benefit from secrecy, I added encription, using rotor.
It also does atomic saves (that means the users can't open the file before it's completely saved).
How easy it was to do those things shows just how neat the Python Standard Library is.
I don't think the code is very nice, and there may even be serious bugs in it. If you figure out some problem, just let me know!
While this module depends on PyQt, a PyKDE (or PyGTK or whatever) version should be trivial. So should be a version for CLI apps, I suppose.
Simple scripts to change passwords on encrypted files, or decrypt them, or compress or uncompress them should be obvious.
Maybe someone want to contribute a script that does all the above (hint hint wink wink :-)
Here's the source
##~ Copyright (c) 2004 Roberto Alsina <ralsina@kde.org>
##~
##~ Permission is hereby granted, free of charge, to any person obtaining a
##~ copy of this software and associated documentation files (the
##~ "Software"), to deal in the Software without restriction, including
##~ without limitation the rights to use, copy, modify, merge, publish,
##~ distribute, sublicense, and/or sell copies of the Software, and to permit
##~ persons to whom the Software is furnished to do so, subject to the
##~ following conditions:
##~
##~ The above copyright notice and this permission notice shall be included
##~ in all copies or substantial portions of the Software.
##~
##~ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
##~ OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
##~ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
##~ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
##~ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
##~ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
##~ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
This module contains functions implementing a generic open/save
interface for applications. It supports regular, compressed and/or
encrypted files, without having to make your application more complex.
As long as you can pickle your data into a string, this should be easy
to use and just work.
The compressed files are compressed using python's zlib, the encryption
is made using python's rotor.
If you don't do autosaves, and you don't mind the user having to type
the password on all save operations, you can happily ignore the "key"
parameters and return values, and everything should work anyway.
The save is atomic: First we save to a temporal file, then rename it
into the desired name. This is so noone can open the file while it's not
completely saved.
KNOWN ISSUES:
* It will use lots of memory for a large file, because it keeps it fully
in memory (won't fix)
* A file encrypted with a null password is not encrypted (won't fix)
* Compressed files are not gunzip/gzip compatible. (may fix)
* No way to choose the filtering in the save dialog (may fix)
* Could be cleaner by removing all dialog code and/or making it optional
and/or adding more functions for it. (won't fix)
"""
__author__ = 'Roberto Alsina <ralsina@kde.org>'
__license__ = 'MIT/X11'
import qt
import zlib
import traceback
import tempfile
import os
import shutil
def encrypt(data,key=None):
"""
Helper function, encrypts data using key, with a 12-wheel rotor.
Returns the encrypted data. If key==None, it's not encrypted
"""
if not key: #No key, no encryption
return data
import rotor
rt=rotor.newrotor(key,12)
return rt.encrypt(data)
def decrypt(data,key=None):
"""
Helper function, decrypts data using key, with a 12-wheel rotor
Returns the decrypted data. Remember that decryption ALWAYS returns
something. I suggest you use some magic cookie at the beginning
to see if the data returned makes sense.
If key==None, it's not decrypted
"""
if not key: #No key, no encryption
return data
import rotor
rt=rotor.newrotor(key,12)
return rt.decrypt(data)
def saveFile(fname,data,key=None):
"""
data: a string containing the data to ve saved.
fname: name of the file where you want to save.
If the name ends in .comp, it will be saved compressed using zlib.
If the name ends in .rotor, it will be saved encrypted using the key.
If the name ends in .comp.rotor, it will be compressed, then
encrypted.
Using .rotor.comp makes no sense, because encrypted files don't
compress at all, so it's not supported.
key is a string used for rotor encryption
If a key is required but not provided, a dialog will popup asking
for it.
If there is an error when compressing, or writing, or anything else,
it will popup a error message.
The return value on success will be True,key with key being the
encription key or None.
On error, it will return False,key with key being the encription
key or None.
"""
tempfile.tempdir=os.path.dirname(fname)
tname=tempfile.mktemp()
if os.access(fname,os.W_OK) or not os.access(fname,os.F_OK):
extensions=fname.split('.')
try:
if extensions[-2]=='comp' or extensions[-1]=='comp': #A compressed file
data=zlib.compress(data,9)
if extensions[-1]=='rotor': #A rotor-crypted file
if not key:
(key,ok)=qt.QInputDialog.getText("Notty - Password",
"Please enter the password",
qt.QLineEdit.Password)
if ok:
key=str(key)
data=encrypt(data,key)
f=open(tname,'wb')
f.write(data)
f.flush()
f.close()
if os.access(fname,os.F_OK): #File exists
shutil.copymode(fname,tname)
os.rename(tname,fname)
return (True,key)
except:
traceback.print_exc()
try:
os.unlink(tname)
except:
# There really isn't much we can do :-)
pass
QMessageBox.critical(None,'Error - Notty',
'Error writing to file "%s"'%fname,'Ok')
return (False,key)
def openFile(fname,key=None):
"""
fname: name of the file you want to open. If no name is given,
the standard file dialog will pop, asking for one.
If the name ends in .comp, it will be uncompressed using zlib.
If the name ends in .rotor, it will be decrypted using the key.
If the name ends in .comp.rotor, it will be decrypted, then
uncompressed.
Using .rotor.comp makes no sense, because encrypted files don't
compress at all, so it's not supported.
key is a string used for rotor encryption
If a key is required but not provided, a dialog will popup asking
for it.
Decrypting will **never** fail, so remember that when you process
the code, maybe all you get is garbage, so implement some error
checking ;-)
If there is an error when decompressing, or reading, or anything
else, it will popup a error message.
The return value on success will be filename,key with key being
the encription key or None.
On error, it will return '',key with key being the encription
key or None.
"""
if fname=='': #Empty filename, ask for one
fname=str(qt.QFileDialog.getOpenFileName(os.getcwd()))
if not fname:
return None
else:
return openFile(fname)
extensions=fname.split('.')
if os.access(fname,os.F_OK) and os.access(fname,os.R_OK):
f=open(fname,'rb')
data=f.read()
pos=-1
if extensions[pos]=='rotor':
if not key:
(key,ok)=qt.QInputDialog.getText("Notty - Password",
"Please enter the password",
qt.QLineEdit.Password)
key=str(key)
if not key or not ok: #No key, no need to decrypt
pass
else:
data=decrypt(data,key)
pos=-2
if extensions[pos]=='comp': #Compressed file
data=zlib.decompress(data)
return data,key
elif not (os.access(fname,os.F_OK)): #File doesn't exist
try:
f=open(fname,'wb') #But we can create it
return '',key
except: #And we can't create it
pass
qt.QMessageBox.critical(None,'Error - Notty',
'Error reading file "%s"'%fname,'Ok')
return False
def saveAsFile(data,key):
"""
data is a string containing the data to be saved.
key is a string used for rotor encryption
It will popup a file dialog asking for a filename to save, then will
call saveFile with that filename.
If a key is required but not provided, a dialog will popup asking
for it.
The return value on success will be True,filename,key with key being
the encription key or None.
On error, it will return False,filename,key with key being the
encription key or None.
"""
fname=str(qt.QFileDialog.getSaveFileName(os.getcwd()))
if not fname:
return False,'',None
else:
status,key=saveFile(fname,data,key)
return status,key,fname
##~
##~ Permission is hereby granted, free of charge, to any person obtaining a
##~ copy of this software and associated documentation files (the
##~ "Software"), to deal in the Software without restriction, including
##~ without limitation the rights to use, copy, modify, merge, publish,
##~ distribute, sublicense, and/or sell copies of the Software, and to permit
##~ persons to whom the Software is furnished to do so, subject to the
##~ following conditions:
##~
##~ The above copyright notice and this permission notice shall be included
##~ in all copies or substantial portions of the Software.
##~
##~ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
##~ OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
##~ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
##~ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
##~ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
##~ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
##~ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
This module contains functions implementing a generic open/save
interface for applications. It supports regular, compressed and/or
encrypted files, without having to make your application more complex.
As long as you can pickle your data into a string, this should be easy
to use and just work.
The compressed files are compressed using python's zlib, the encryption
is made using python's rotor.
If you don't do autosaves, and you don't mind the user having to type
the password on all save operations, you can happily ignore the "key"
parameters and return values, and everything should work anyway.
The save is atomic: First we save to a temporal file, then rename it
into the desired name. This is so noone can open the file while it's not
completely saved.
KNOWN ISSUES:
* It will use lots of memory for a large file, because it keeps it fully
in memory (won't fix)
* A file encrypted with a null password is not encrypted (won't fix)
* Compressed files are not gunzip/gzip compatible. (may fix)
* No way to choose the filtering in the save dialog (may fix)
* Could be cleaner by removing all dialog code and/or making it optional
and/or adding more functions for it. (won't fix)
"""
__author__ = 'Roberto Alsina <ralsina@kde.org>'
__license__ = 'MIT/X11'
import qt
import zlib
import traceback
import tempfile
import os
import shutil
def encrypt(data,key=None):
"""
Helper function, encrypts data using key, with a 12-wheel rotor.
Returns the encrypted data. If key==None, it's not encrypted
"""
if not key: #No key, no encryption
return data
import rotor
rt=rotor.newrotor(key,12)
return rt.encrypt(data)
def decrypt(data,key=None):
"""
Helper function, decrypts data using key, with a 12-wheel rotor
Returns the decrypted data. Remember that decryption ALWAYS returns
something. I suggest you use some magic cookie at the beginning
to see if the data returned makes sense.
If key==None, it's not decrypted
"""
if not key: #No key, no encryption
return data
import rotor
rt=rotor.newrotor(key,12)
return rt.decrypt(data)
def saveFile(fname,data,key=None):
"""
data: a string containing the data to ve saved.
fname: name of the file where you want to save.
If the name ends in .comp, it will be saved compressed using zlib.
If the name ends in .rotor, it will be saved encrypted using the key.
If the name ends in .comp.rotor, it will be compressed, then
encrypted.
Using .rotor.comp makes no sense, because encrypted files don't
compress at all, so it's not supported.
key is a string used for rotor encryption
If a key is required but not provided, a dialog will popup asking
for it.
If there is an error when compressing, or writing, or anything else,
it will popup a error message.
The return value on success will be True,key with key being the
encription key or None.
On error, it will return False,key with key being the encription
key or None.
"""
tempfile.tempdir=os.path.dirname(fname)
tname=tempfile.mktemp()
if os.access(fname,os.W_OK) or not os.access(fname,os.F_OK):
extensions=fname.split('.')
try:
if extensions[-2]=='comp' or extensions[-1]=='comp': #A compressed file
data=zlib.compress(data,9)
if extensions[-1]=='rotor': #A rotor-crypted file
if not key:
(key,ok)=qt.QInputDialog.getText("Notty - Password",
"Please enter the password",
qt.QLineEdit.Password)
if ok:
key=str(key)
data=encrypt(data,key)
f=open(tname,'wb')
f.write(data)
f.flush()
f.close()
if os.access(fname,os.F_OK): #File exists
shutil.copymode(fname,tname)
os.rename(tname,fname)
return (True,key)
except:
traceback.print_exc()
try:
os.unlink(tname)
except:
# There really isn't much we can do :-)
pass
QMessageBox.critical(None,'Error - Notty',
'Error writing to file "%s"'%fname,'Ok')
return (False,key)
def openFile(fname,key=None):
"""
fname: name of the file you want to open. If no name is given,
the standard file dialog will pop, asking for one.
If the name ends in .comp, it will be uncompressed using zlib.
If the name ends in .rotor, it will be decrypted using the key.
If the name ends in .comp.rotor, it will be decrypted, then
uncompressed.
Using .rotor.comp makes no sense, because encrypted files don't
compress at all, so it's not supported.
key is a string used for rotor encryption
If a key is required but not provided, a dialog will popup asking
for it.
Decrypting will **never** fail, so remember that when you process
the code, maybe all you get is garbage, so implement some error
checking ;-)
If there is an error when decompressing, or reading, or anything
else, it will popup a error message.
The return value on success will be filename,key with key being
the encription key or None.
On error, it will return '',key with key being the encription
key or None.
"""
if fname=='': #Empty filename, ask for one
fname=str(qt.QFileDialog.getOpenFileName(os.getcwd()))
if not fname:
return None
else:
return openFile(fname)
extensions=fname.split('.')
if os.access(fname,os.F_OK) and os.access(fname,os.R_OK):
f=open(fname,'rb')
data=f.read()
pos=-1
if extensions[pos]=='rotor':
if not key:
(key,ok)=qt.QInputDialog.getText("Notty - Password",
"Please enter the password",
qt.QLineEdit.Password)
key=str(key)
if not key or not ok: #No key, no need to decrypt
pass
else:
data=decrypt(data,key)
pos=-2
if extensions[pos]=='comp': #Compressed file
data=zlib.decompress(data)
return data,key
elif not (os.access(fname,os.F_OK)): #File doesn't exist
try:
f=open(fname,'wb') #But we can create it
return '',key
except: #And we can't create it
pass
qt.QMessageBox.critical(None,'Error - Notty',
'Error reading file "%s"'%fname,'Ok')
return False
def saveAsFile(data,key):
"""
data is a string containing the data to be saved.
key is a string used for rotor encryption
It will popup a file dialog asking for a filename to save, then will
call saveFile with that filename.
If a key is required but not provided, a dialog will popup asking
for it.
The return value on success will be True,filename,key with key being
the encription key or None.
On error, it will return False,filename,key with key being the
encription key or None.
"""
fname=str(qt.QFileDialog.getSaveFileName(os.getcwd()))
if not fname:
return False,'',None
else:
status,key=saveFile(fname,data,key)
return status,key,fname
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