|
Hi,
Is there a data type wchar_t in C?If so, how it differ from char?
|
|
|
|
|
Quote: Is there a data type wchar_t in C?
Yes, apparently[^].
Quote: If so, how it differ from char?
It is compiler dependent.
|
|
|
|
|
|
Thanks. I tried finding size of it and got 4 bytes. If so, It should be able to take something like "abc". But its not happening. Why?
|
|
|
|
|
Because "abc" is a char* string and not a wchar_t which represents a single character.
wchar_t are used to store fixed length Unicode characters like UTF-16 or UTF-32 while char can store fixed length ASCII or ANSI characters (with an associated code page) or variable length characters like UTF-8 or Microsoft multi byte characters.
|
|
|
|
|
Jochen Arndt wrote: wchar_t are used to store fixed length Unicode characters like UTF-16 or UTF-32
Just noting that statement is somewhat of a generalization.
For starters, unicode, for those bit sizes never represents all characters via single character. One needs to go to 128 bits for a full representation. Maybe that isn't even big enough.
Additionally it is not limited to unicode. Although perhaps these days that would be the predominant usage in the western world.
|
|
|
|
|
Quote: "wchar_t are used to store fixed length Unicode characters like UTF-16 or UTF-32"
Just noting that statement is somewhat of a generalization.
Why? As far as I know wchar_t is not used for variable length encodings.
jschell wrote: for those bit sizes never represents all characters via single character
While that is true for UTF-16 it is not for UTF-32.
jschell wrote: One needs to go to 128 bits for a full representation
That is wrong.
Tuesday, June 20, 2017
Version 10.0 of the Unicode Standard is now available. For the first time, both the core specification and the data files are available on the same date. Version 10.0 adds 8,518 characters, for a total of 136,690 characters. These additions include four new scripts, for a total of 139 scripts, as well as 56 new emoji characters. Still 14 of 32 bits unused.
|
|
|
|
|
Jochen Arndt wrote: Why? As far as I know wchar_t is not used for variable length encodings.
It is intended for any character set, not just unicode. Most representations are not unicode.
And unicode IS a variable length encoding to some meaning of that definition. There are escape characters in the 8/16/32 bit unicode character sets that allow for the definition of additional characters using multiple 'character' values. So two wchar_t might be needed for a single character.
Jochen Arndt wrote: While that is true for UTF-16 it is not for UTF-32.
"UTF-32 does not make calculating the displayed width of a string easier, since even with a "fixed width" font there may be more than one code point per character position"
UTF-32 - Wikipedia[^]
I will state that it is unlikely for this to be used.
Jochen Arndt wrote: That is wrong.
Presumably you are claiming that UTF-32 contains every possible character.
So based on that logic what exactly is in UTF-64? Just UTF-32 for the first half and the empty space for the rest?
Jochen Arndt wrote: Still 14 of 32 bits unused.
That isn't relevant. It isn't how the character set is defined but rather the extent and how it is used.
There are unused spots in a number of places in unicode in general. No idea why. Perhaps they figure a specific range of the character set might have a few more characters added in the future.
Far as I can recall many character sets beyond 7 bits end up duplicating or adding to a real character set. For example the normal extended ascii set has several dashes and a few mathematical symbols. And that is only using 8 bits.
|
|
|
|
|
Quote: It is intended for any character set, not just unicode. Most representations are not unicode.
Examples (I don't know one except when wchar_t is defined as char)?
Quote: And unicode IS a variable length encoding to some meaning of that definition
There are multiple Unicode encodings where some are fixed length and some are variable length.
Quote: So two wchar_t might be needed for a single character.
It is intended to be used for single characters. Allowing more than one requires a much more complex implementation (like with the char based Microsoft multi byte character sets).
Quote: "UTF-32 does not make calculating the displayed width of a string easier, since even with a "fixed width" font there may be more than one code point per character position"
Fonts and there display length is not related to character encoding specifications.
Quote: That isn't relevant. It isn't how the character set is defined but rather the extent and how it is used.
It is all about the definition regarding the required storage size.
The unused code points are there because the codes are grouped (each script or symbol type has an assigned range). See Unicode block - Wikipedia[^]. So new characters / symbols can be added later to the belonging group (a rather old example is the Euro symbol).
The grouping has been choosen because with 32 bits there is enough room. Unicode already contains nearly all known scripts including ancient ones like Runes and Mayan glyphs and a wide range of symbols.
|
|
|
|
|
Jochen Arndt wrote: The grouping has been choosen because with 32 bits there is enough room. Unicode already contains nearly all known scripts including ancient ones like Runes and Mayan glyphs and a wide range of symbols.
As I said there is a 64 bit definition. Left to you to explain what the purpose of that is.
|
|
|
|
|
I can't explain the purpose of something that does not exist. There is neither UTF-64 nor UTF-128.
|
|
|
|
|
Jochen Arndt wrote: There is neither UTF-64 nor UTF-128.
I stand corrected - far as I can tell there is no 64 bit encoding.
However there still remains code points in the 32 bit set that require a total of two code points.
|
|
|
|
|
fixed length Unicode characters like UTF-16 or UTF-32-A detailed explanation will be helpful.And any example for them?
|
|
|
|
|
wchar_t are used to store "wide characters" (characters using an encoding that requires more than a byte). The most common used character encodings for wchar_t are UCS-2 (a subset of UTF-16) and UTF-32.
Read Unicode - Wikipedia[^].
|
|
|
|
|
|
It's defined as a wide char for Unicode & UTF16 support primarily for filename name support (FAT32 LFN for example) and foreign console input.
There is also another important type in <wchar.h> which is wint_t which is the generic carrier form.
You need the concept of narrowing which take a wide character back to it's byte approximation (see function wctob).
wctob | Microsoft Docs[^]
The reverse concept is widening which takes a byte character and promotes it (see function btowc)
btowc | Microsoft Docs[^]
The letter conversions are controlled by the current LC_TYPE locale meaning the language type
Type something like this .. it prints the time in japanese 
#include <wchar.h>
#include <locale.h>
#include <time.h>
int main(void){
wchar_t str[100];
time_t t = time(0);
setlocale(LC_ALL, "ja-JP");
wcsftime(str, 100, L"%A %c", localtime(&t));
wprintf(L"%Ls\n", str);
}
It will look something like "金曜日 2017/12/15 2:09:13"
In vino veritas
|
|
|
|
|
Newer versions of Visual Studio are installed without a makefile for the MFC library.
As I want to change some inner parts of MFC I need to compile the library.
...but without a makefile (or solution file) this is not possible.
Anybody out there which has got a working makefile for newer Visual Studios?
Regards,
jung-kreidler
|
|
|
|
|
jung-kreidler wrote: As I want to change some inner parts of MFC I need to compile the library.
Is this something you've (had) done before?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
|
|
|
|
|
Yes, some years ago with an older version of MFC as there was a bug inside...
Thanks for the response.
|
|
|
|
|
Don't, it could lead to all sorts of problems. A much better idea is to add your changes by subclassing the classes that you need to behave differently.
|
|
|
|
|
The reason for trying to get the hands on the MFC source are necessary changes (public vs. protected...) in the feature pack. Subclassing it not possible as the corresponding classes are already subclassed by the MFC feature pack itself. So, there's no access to the inner parts.
Thanks for the response!
|
|
|
|
|
Hi,
Note that I have not used MFC since ~2013 but I can tell you that you can simply copy the MAK files from the VS2008 installation folder into your VS2010-VS2012 source folder and make a few changes. I have never attempted for VS2013 and above.
I believe the last version that supported recompile of the MFC framework was VC2008 with 'nmake /f atlmfc.mak MFC' from commandline. Beginning with version MSVC2010 the MAK files were removed and recompile of the library became completely unsupported.
Best Wishes,
-David Delaune
|
|
|
|
|
Thank you all for answering. I did the VS2008 makefile way. There were a lot of new afx...cpp files to add. It did compile (and yes, it worked fine at a first glance) and I tried to go further into the replacement of some feature pack subclassed windows. Finally I've stopped as there were too many changes necessary, which might cause side effects.
Just wanted to get the beautiful MDI tear off feature of newer VS. 
|
|
|
|
|
Hi,
I have created a system level service which needs APPDATA folder path which is different for each user. Is there anyway through which I can get the logged in user APPDATA folder path?
|
|
|
|
|
It is possible to get the name of logged in users from a service (you have already asked that and got an answer). Using that you can guess the the user directory path and verify it by checking if the pathe exists.
But a service should not modify user data and usually does not need to read user data.
You have not told us why you need access to user directories. Maybe there is a better solution for your problem.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
