Re: C string to D without memory allocation?

[Rikki Cattermole via Digitalmars-d-learn]

On 21/12/15 6:34 PM, Shriramana Sharma wrote:
Hello. I have the following code:
import std.stdio, std.conv;
extern(C) const(char) * textAttrN(const (char) * specString, size_t n);
string textAttr(const(char)[] specString)
{
     const(char) * ptr = textAttrN(specString.ptr, specString.length);
     writeln(ptr);
     return to!string(ptr);
}
void main()
{
     auto s = textAttr("w /g");
     writeln(s.ptr);
}

Now I'm getting different pointer values printed, like:

7F532A85A440
7F532A954000

Is it possible to get D to create a D string from a C string but not
allocate memory?

I thought perhaps the allocation is because C does not guarantee
immutability but a D string has to. So I tried changing the return type of
textAttr to const(char)[] but I find it is still allocating for the return
value. Is this because a slice can potentially be appended to but it may
overflow a C buffer?

Finally, I just want to return a safe D type encapsulating a C string but
avoid allocation – is it possible or not?

Thanks!

size_t strLen = ...;
char* ptr = ...;

string myCString = cast(string)ptr[0 .. strLen];

I can't remember if it will include the null terminator or not, but if 
it does just decrease strLen by 1.