On Tuesday, January 28, 2020 10:17:03 PM MST Marcone via Digitalmars-d-learn wrote: > How to convert "string" to const(wchar)* ? > The code bellow is making confuse strange characters. > > cast(wchar*) str
Of course it is. string is immutable(char)[], and the characters are in UTF-8. immutable(wchar)[] would would be UTF-16. Even casting between those two types would result in nonsense, because UTF-8 and UTF-16 are different encodings. Casting between array or pointer types basically causes one type to be interpreted as the other. It doesn't convert the underlying data in any fashion. Also, strings aren't null-terminated in D, so having a pointer to a random string could result in a buffer overflow when you try to iterate through the string via pointer as is typical in C code. D code just uses the length property of the string. I assume that with const(wchar)*, you want it to be a null-terminated string of const(wchar). For that, what you basically need is a const(wchar)[] with a null terminator, and then you need to get a pointer to its first character. So, if you were to do that yourself, you'd end up with something like wstring wstr = to!wstring(str) ~ '\0'; const(wchar)* cwstr = wstr.ptr; or more likely auto = to!wstring(str) ~ '\0'; auto cwstr = wstr.ptr; The function in the standard library for simplifying that is toUTF16z: https://dlang.org/phobos/std_utf.html#toUTF16z Then you can just do auto cwstr = str.toUTF16z(); However, if you're doing this to pass a null-terminated string of UTF-16 characters to a C program (e.g. to the Windows API), be aware that if that function stores that pointer anywhere, you will need to also store it in your D code, because toUTF16z allocates a dynamic array to hold the string that you're getting a pointer to, and if a C function holds on to that pointer, the D GC won't see that it's doing that. And if the D GC doesn't see any references to that array anywhere, it will likely collect that memory. As long as you're passing it to a C function that just operates on the memory and returns, it's not a problem, but it can definitely be a problem if the C function stores that pointer even after the function has returned. Keeping a pointer to that memory in your D code fixes that problem, because then the D GC can see that that memory is still referenced and thus should not be collected. - Jonathan M Davis
