On Monday, 21 December 2015 at 05:34:07 UTC, 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!
Use std.string.fromStringz. to!string assumes that pointers to
characters are null-terminated strings which is not safe or
general (unlike std.format, which safely assumes they are
pointers to single characters); it is a poor design. fromStringz
is explicit about this assumption.
That said, to!string shouldn't allocate when given
immutable(char)*.
