I'm developing an application that needs to be able to create & manipulate SQLite databases in user-defined paths. I'm running into a problem I don't really understand. I'm testing my stuff against some really gross sample data with huge unwieldy unicode paths, for most of them there isn't a problem, but for one there is.
An example of a working connection string is:
Data Source="c:\test6\意外な高価で売れるかも？ 出品は手順を覚えれば後はかんたん！\11オークションストアの出品は対象外とさせていただきます。\test.db";Version=3;
While one that fails is
Data Source="c:\test6\意外な高価で売れるかも？ 出品は手順を覚えれば後はかんたん！\22今やPCライフに欠かせないのがセキュリティソフト。そのため、現在何種類も発売されているが、それぞれ似\test.db";Version=3;
I'm using System.Data.SQLite v1.0.66.0 due to reasons outside of my control, but I quickly tested with the latest, v1.0.77.0 and had the same problems.
Both when attempting to newly create the test.db file or if I manually put one there and it's attempting to open, SQLiteConnection.Open throws an exception saying only "Unable to open the database file", with the stack trace showing that it's actually System.Data.SQLite.SQLite3.Open that is throwing.
Is there any way I can get System.Data.SQLite to play nicely with these paths? A workaround could be to create and manipulate my databases in a temporary location and then just move them to the actual locations for storage, since I can create and manipulate files normally otherwise. That's kind of a last resort though.
Thank you.
I am guessing you are on a Japanese-locale machine where the default system encoding (ANSI code page) is cp932 Japanese (≈Shift-JIS).
The second path contains:
ソ
which encodes to the byte sequence:
0x83 0x5C
Shift-JIS is a multibyte encoding that has the unfortunate property of sometimes re-using ASCII code units in the trail byte. In this case it has used byte 0x5C which corresponds to the backslash \. (Though this typically displays as a yen sign in Japanese fonts, for historical reasons.)
So if this pathname is passed into a byte-based API, it will get encoded in the ANSI code page, and you won't be able to tell the difference between a backslash meant as a directory separator and one that is a side-effect of multi-byte encoding. Consequently any path with one of the following characters in will fail when accessed with a byte-based IO method:
―ソЫⅨ噂浬欺圭構蚕十申曾箪貼能表暴予禄兔喀媾彌拿杤歃畚秉綵臀藹觸軆鐔饅鷭偆砡纊犾
(Also any pathname that contains a Unicode character not present in cp932 will naturally fail.)
It would appear that behind the scenes SQLite is using a byte-based IO method to open the filename it is given. This is unfortunate, but extremely common in cross-platform code, because the POSIX C standard library is defined to use byte-based filenames for operations like file open().
Consequently using the C stdlib functions it is impossible to reliably access files with non-ASCII names. This sad situation inherits into all sorts of cross-platform libraries and languages written using the stdlib; only tools written with specific support for Win32 Unicode filenames (eg Python) can reliably access all files under Windows.
Your options, then, are:
avoid using non-ASCII characters in the path name for your db, as per the move/rename suggestion;
continue to rely on the system locale being Japanese (ANSI code page=932), and just rename files to avoid any of the characters listed above;
get the short (8.3) filename of the file in question and use that instead of the real one—something like c:\test6\85D0~1\22PC~1\test.db. You can use dir /x to see the short-filenames. They are always pure ASCII, avoiding the encoding problem;
add some code to get the short filename from the real one, using GetShortPathName. This is a Win32 API so you need a little help to call it from .NET. Note also short filenames will still fail if run on a machine with the short filename generation feature disabled;
persuade SQLite to add support for Windows Unicode filenames;
persuade Microsoft to fix this problem once and for all by making the default encoding for byte interfaces UTF-8, like it is on all other modern operating systems.
Related
I am learning to build GUIs using PyQt5 (on Windows).
I came accross a piece of code with explicit translation into UTF8 in PyQt4 (not PyQt5):
a=QApplication(args)
button=QPushButton(a.trUtf8("éàùè"),None)
After a little bit of googling I found that trUtf8 is deprecated and that now Qt5 assumes that your code is already UTF8 formatted (link):
QObject::trUtf8() and QCoreApplication::Encoding are deprecated. Qt assumes that the source code is encoded in UTF-8.
So, I'd like to know what I should do to comply with this statement.
Even if I am not looking for a vim oriented solution, I'd like to add that I am using Vim to develop my code. So, I added the following options to my setup:
set encoding=utf-8
set fileencoding=utf-8
Is it correct, is it enough?
More generally, what do you need to be UTF8 compliant with Qt5?
Thank you!
The tr function has nothing to do with encoding/decoding per se - it is used for marking out which literal strings may require translation in applications which support multiple languages (if you're familiar with gnu gettext, it performs a similar role to the _() function).
Strings which are marked for translation will only get translated if a translator is installed. Otherwise, the strings will be passed through unchanged. The encoding/decoding aspect only comes into play because the C++ functions take in the source strings as const char* (i.e. bytes) and return a QString (i.e. unicode). So if there is no translation available, and the source string contains non-ASCII characters, a default decoding step would need to be performed. In Qt4, this had to be done explicitly with trUtf8 under some circumstances (see the docs for details) - but in Qt5 it can all handled by the tr function alone.
If you're using Python 3 with PyQt5, you can pretty much forget about all these issues, because literal strings are unicode by default, and UTF-8 is assumed as the source-code encoding. Also, PyQt5 will always return a python unicode object for any Qt function that would normally return a QString.
And of course, if you never intend to support multiple languages in your application, you can safely omit all usage of tr, as it would otherwise perform no useful function.
I can't find anything on Google for some tool that encrypts/obfuscates my lua files, so I decided to ask here. Maybe some professional knows how to do it? (For free).
I have made a simple game in lua now and I don't want people to see the code, otherwise they can easily cheat. How can I make the whole text inside the .lua file to just random letters and stuff?
I used to program in C# and I had this .NET obfuscator called SmartAssembly which works pretty good. When someone would try check the code of my applications it would just be a bunch of letters and numbers together with chinese characters and stuff.
Anyone knows any program that can do this for lua aswell? Just load what file to encrypt, click Encrypt or soemthing, and bam! It works!?
For example this:
print('Hello world!')
would turn into something like
sdf9sd###&/sdfsdd9fd0f0fsf/&
Just precompile your files (chunks) and load binary chunks. luacallows you to strip debugging info. If that is not enough, define your own transformations on the compiled lua, stripping names where possible. There's not really so much demand for lua obfuscators though...
Also, you loose one of the main advantages of using an embedded scripting language: Extensibility.
The simplest obfuscation option is to compile your Lua code as others suggested, however it has two major issues: (1) the strings are still likely to be easily visible in your compiled code, and (2) the compiled code for Lua interpreter is not portable, so if you target different architectures, you need to have different compiled chunks for them.
The first issue can be addressed by using a pre-processor that (for example) converts your strings to a sequence of numbers and then concatenates them back at run-time.
The second issue is not easily addressed without changes to the interpreter, but if you have a choice of interpreters, then LuaJIT generates portable bytecode that will run across all its platforms (running the same version of LuaJIT); note that LuaJIT bytecode is different from Lua bytecode, so it can't be run by a Lua interpreter.
A more complex option would be to encrypt the code (possibly before compiling it), but you need to weight any additional mechanisms (and work on your part) against any possible inconvenience for your users and any loss you have from someone cracking the protection. I'd personally use something sufficiently simple to deter the majority of curious users as you likely stand no chance against a dedicated hacker anyway.
You could use loadstring to get a chunk then string.dump and then apply some transformations like cycling the bytes, swapping segments, etc. Transformations must be reversible. Then save to a file.
Note that anyone having access to your "encryptor" Lua module will know how to decrypt your file. If you make your encrypted module in C/C++, anyone with access to source will too, or to binary of Lua encryption module they could require the module too and unofuscate the code. With interpreted language it is quite difficult to do: you can raise the bar a bit via the above the techniques but raising it to require a significant amount of work (the onlybreal deterent) is very difficult AFAIK.
If you embed the Lua interpreter than you can do this from C, this makes it significantly harder (assuming a Release build with all symbols stripped), person would have to be comfortable with stepping through assembly but it only takes one capable person to crack the algorithm then they can make the code available to others.
Yo still interested in doing this? :)
I thought I'd add some example code, since the answers here were helpful, but didn't get us all the way there. We wanted to save some lua table information, and just not make it super easy for someone to inject their own code. serialize your table, and then use load(str) to make it into a loadable lua chunk, and save with string.dump. With the 'true' parameter, debug information is stripped, and there's really not much there. Yes you can see string keys, but it's much better than just saving the naked serialized lua table.
function tftp.SaveToMSI( tbl, msiPath )
assert(type(tbl) == "table")
assert(type(msiPath) == "string")
local localName = _GetFileNameFromPath( msiPath )
local file,err = io.open(localName, "wb")
assert(file, err)
-- convert the table into a string
local str = serializer.Serialize( tbl )
-- create a lua chunk from the string. this allows some amount of
-- obfuscation, because it looks like gobblygook in a text editor
local chunk = string.dump(load(str), true)
file:write(chunk)
file:close()
-- send from /usr to the MSI folder
local sendResult = tftp.SendFile( localName, msiPath )
-- remove from the /usr folder
os.remove(localName)
return sendResult
end
The output from one small table looks like this in Notepad++ :
LuaS У
Vx#w( # АKА└АJБ┴ JА #
& А & name
Coulombmetervalue? С╘ ажў
The mac version of my application has just started breaking its full screen and normal layouts which I save and restore using QSettings. Even old versions of my application are now playing up for my customers.
I was just googling for something similar when I found a bug report which contained an interesting line:
QSettings s;
restoreState(s.value(QString::fromLocal8Bit("state")).toByteArray());
When saving to the computers plist's or windows registry do I have to format the data in this fromLocal8bit()?
http://bugreports.qt-project.org/browse/QTBUG-8631
http://bugreports.qt-project.org/secure/attachment/13400/main.cpp
It's the data that is encoded, it's just the literal "state". The values are properly encoded and decoded if you use QByteArray or QString
.
The QString::fromLocal8Bit() part is for converting the string literal in the source file to a unicode string. It's good practice to stick to ASCII in source files, as other encodings such as UTF-8 usually don't work with all compilers, especially MSVC.
To convert literals to QString I would suggest using QLatin1String:
QLatin1String("state")
fromLocal8Bit() is strictly speaking false, as the local 8bit encoding has nothing to do with the source file encoding, where the literal comes from.
But as "state" doesn't contain any non-ascii characters, it shouldn't matter anyway.
I created a simple test page on my website www.xaisoft.com and it had no errors, but it came back with the following warning and I am not sure what it means.
The Unicode Byte-Order Mark (BOM) in UTF-8 encoded files is known to cause problems for some text editors and older browsers. You may want to consider avoiding its use until it is better supported.
To find out what the BOM is, you can take a look at the Unicode FAQ (quoting) :
Q: What is a BOM?
A: A byte order mark (BOM) consists of
the character code U+FEFF at the
beginning of a data stream, where it
can be used as a signature defining
the byte order and encoding form,
primarily of unmarked plaintext files.
Under some higher level protocols, use
of a BOM may be mandatory (or
prohibited) in the Unicode data stream
defined in that protocol.
Depending on your editor, you might find an option in the preferences to indicate it should save unicode documents without a BOM... or change editor ^^
Some text editors - notably Notepad - put an extra character at the front of the text file to indicate that it's Unicode and what byte-order it is in. You don't expect Notepad to do this sort of thing, and you don't see it when you edit with Notepad. You need to open the file and explicitly resave it as ANSI. If you're using fancy characters like smart quotes, trademark symbols, circle-r, or that sort of thing, don't. Use the HTML entities instead.
Has anyone had experience generating files that have filenames containing non-ascii international language characters?
Is doing this an easy thing to achieve, or is it fraught with danger?
Is this functionality expected from Japanese/Chinese speaking web users?
Should file extensions also be international language characters?
Info: We currently support multilanguage on our site, but our filenames are always ASCII. We are using ASP.NET on the .NET framework. This would be used in a scenario where international users could choose a common format and name for there files.
Is this functionality expected from Japanese/Chinese speaking web users?
Yes.
Is doing this an easy thing to achieve, or is it fraught with danger?
There are issues. If you are serving files directly, or otherwise have the filename in the URL (eg.: http://www.example.com/files/こんにちは.txt -> http://www.example.com/files/%E3%81%93%E3%82%93%E3%81%AB%E3%81%A1%E3%81%AF.txt), you're generally OK.
But if you're serving files with the filename generated by the script, you can have problems. The issue is with the header:
Content-Disposition: attachment;filename="こんにちは.txt"
How do we encode those characters into the filename parameter? Well it would be nice if we could just dump it in in UTF-8. And that will work in some browsers. But not IE, which uses the system codepage to decode characters from HTTP headers. On Windows, the system codepage might be cp1252 (Latin-1) for Western users, or cp932 (Shift-JIS) for Japanese, or something else completely, but it will never be UTF-8 and you can't really guess what it's going to be in advance of sending the header.
Tedious aside: what does the standard say should happen? Well, it doesn't really. The HTTP standard, RFC2616, says that bytes in HTTP headers are ISO-8859-1, which wouldn't allow us to use Japanese. It goes on to say that non-Latin-1 characters can be embedded in a header by the rules of RFC2047, but RFC2047 explicitly denies that its encoded-words can fit in a quoted-string. Normally in RFC822-family headers you would use RFC2231 rules to embed Unicode characters in a parameter of a Content-Disposition (RFC2183) header, and RFC2616 does defer to RFC2183 for definition of that header. But HTTP is not actually an RFC822-family protocol and its header syntax is not completely compatible with the 822 family anyway. In summary, the standard is a bloody mess and no-one knows what to do, certainly not the browser manufacturers who pay no attention to it whatsoever. Hell, they can't even get the ‘quoted-string’ format of ‘filename="..."’ right, never mind character encodings.
So if you want to serve a file dynamically with non-ASCII characters in the name, the trick is to avoid sending the ‘filename’ parameter and instead dump the filename you want in a trailing part of the URL.
Should file extensions also be international language characters?
In principle yes, file extensions are just part of the filename and can contain any character.
In practice on Windows I know of no application that has ever used a non-ASCII file extension.
One final thing to look out for on systems for East Asian users: you will find them typing weird, non-ASCII versions of Latin characters sometimes. These are known as the full-width and half-width forms, and are designed to allow Asians to type Latin characters that line up with the square grid used by their ideographic (Han etc.) characters.
That's all very well in free text, but for fields you expect to parse as Latin text or numbers, receiving an unexpected ‘４２’ integer or ‘．ｔｘｔ’ file extension can trip you up. To convert these ‘compatibility characters’ down to plain Latin, normalise your strings to ‘Unicode Normal Form NFKC’ before doing anything with them.
Refer to this overview of file name limitations on Wikipedia.
You will have to consider where your files will travel, and stay within the most restrictive set of rules.
From my experience in Japan, filenames are typically saved in Japanese with the standard English extension. Apply the same to any other language.
The only problem you will run into is that in an unsupported environment for that character set, people will usually just see a whole bunch of squares with an extension. Obviously this won't be a problem for your target users.
I have been playing around with Unicode and Indian languages for a while now. Here are my views on your questions:
Its easy. You will need two things: Enable Unicode (UTF-8/16/32) support in your OS so that you can type those characters and get Unicode compatible editors/tools so that your tools understand those characters.
Also, since you are looking at a localised web application, you have to ensure or atleast inform your visitor that he/she needs to have a browser which uses relevant encoding.
Your file extensions need not be i18-ned.
My two cents:
Key thing to international file names is to make URLs like bobince suggested:
www.example.com/files/%E3%81%93%E3%82%93%E3.txt
I had to make special routine for IE7 since it crop filename if its longer then 30 characters. So instead of "Your very long file name.txt" file will appear as "%d4y long file name.txt". However interesting thing is that IE7 actually understands header attachment;filename=%E3%81%93%E3%82%93%E3.txt correctly.