C string to D without memory allocation?
Jakob Ovrum via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Sun Dec 20 21:40:21 PST 2015
On Monday, 21 December 2015 at 05:34:07 UTC, Shriramana Sharma
> 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,
> return to!string(ptr);
> void main()
> auto s = textAttr("w /g");
> Now I'm getting different pointer values printed, like:
> 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?
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
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