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digitalmars.D.learn - Is there an equivalent to toStringz for wide strings?

reply Andrej Mitrovic <none none.none> writes:
I think I'd need a toWStringz function, or maybe toStringz can be made more
clever and figure out that I'm passing a wstring and return a null-terminated
wchar*.

Currently I'm using wstrings and appending the null terminator by hand, e.g.:

wstring appName  = "DMapp" ~ "\0";

Some WinAPI functions in unicode form, such as CreateWindowExW, expect a
wchar*. So in the above case I just pass `appName.ptr`. But it would be
convenient not having to append the null terminator prematurely.
Apr 04 2011
next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On 2011-04-04 16:17, Andrej Mitrovic wrote:

 I think I'd need a toWStringz function, or maybe toStringz can be made more
 clever and figure out that I'm passing a wstring and return a
 null-terminated wchar*.
 
 Currently I'm using wstrings and appending the null terminator by hand,
 e.g.:
 
 wstring appName  = "DMapp" ~ "\0";
 
 Some WinAPI functions in unicode form, such as CreateWindowExW, expect a
 wchar*. So in the above case I just pass `appName.ptr`. But it would be
 convenient not having to append the null terminator prematurely.


Almost all of the string functions are string-specific and don't deal with 
wstring or dstring. Some of them work with multiple string types, but most 
don't - though that may change. In this case, I'd just append the null 
character and be done with it. Not to mention, in the case above, a null 
character should automatically be appended onto the end of the string, since 
it's as string literal (unless wstring or dstring literals are treated 
differently for some reason - you might want to check that). All string 
literals have a null character at one past their end so that they can be 
passed to C functions directly.

Regardless, you should watch out for cases where the function being called 
keeps the pointer that it's passed without copying it but you didn't keep the 
string around, which could cause it to be garbage collected. I've screwed up 
with that before.

In any case, there is no toWStringz in Phobos. You can open up an enhancement 
request for one though.

- Jonathan M Davis
Apr 04 2011
prev sibling next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 4/5/11, Jonathan M Davis <jmdavisProg gmx.com> wrote:

 Not to mention, in the case above, a null
 character should automatically be appended onto the end of the string, since
 it's as string literal.


I've always found this confusing. So If I have this char array:
char[] foostring = "foo".dup;

null is appended to it? So what happens to the null terminator if I
append another string to foostring? And if I do a copy, e.g.
foostring[0..$], does this still copy a null terminator?
Apr 04 2011
prev sibling next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On 2011-04-04 16:44, Andrej Mitrovic wrote:

 On 4/5/11, Jonathan M Davis <jmdavisProg gmx.com> wrote:

 Not to mention, in the case above, a null
 character should automatically be appended onto the end of the string,
 since it's as string literal.


 
 I've always found this confusing. So If I have this char array:
 char[] foostring = "foo".dup;
 
 null is appended to it? So what happens to the null terminator if I
 append another string to foostring? And if I do a copy, e.g.
 foostring[0..$], does this still copy a null terminator?


The null terminator is not actually part of the string. It's one beyond the 
end. In effect, it's "foo"[$] (though that would probably throw as long as 
array bounds checking is turned on). So, any array operations that you do on 
the string will lose the null terminator. It's just that if you pass it to a C 
function or some other function that's going completely off of the pointer 
(rather than the D array) and which hasn't been told the length of the string, 
it's going to see the null terminator at one past the end of the actual array.

So, you can do something like

printf("hello world\n");

or

auto s = "hello world";
printf(s.ptr);

But as soon as you do anything which would cause the array to reallocate or be 
copied, you lose the null terminator. It's not really part of the string. It's 
one past the end of the string and is there purely for convenience when 
dealing with C functions. So, it's lost as soon as you start treating the 
string a as D string and do any array or string operations on it which would 
copy or change it.

- Jonathan M Davis
Apr 04 2011
prev sibling next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
Ok that makes sense. Thank you.
Apr 04 2011
prev sibling parent reply Kagamin <spam here.lot> writes:
Andrej Mitrovic Wrote:


 I think I'd need a toWStringz function, or maybe toStringz can be made more
clever and figure out that I'm passing a wstring and return a null-terminated
wchar*.
 
 Currently I'm using wstrings and appending the null terminator by hand, e.g.:
 
 wstring appName  = "DMapp" ~ "\0";
 
 Some WinAPI functions in unicode form, such as CreateWindowExW, expect a
wchar*. So in the above case I just pass `appName.ptr`. But it would be
convenient not having to append the null terminator prematurely.


toUTF16z
it was in windows examples somewhere, I suppose.
Apr 05 2011
parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 4/5/11, Kagamin <spam here.lot> wrote:

 toUTF16z
 it was in windows examples somewhere, I suppose.


Great, it's in std.utf. Thanks!
Apr 05 2011