Crystal C bindings: return type char*

Question

I have a function with this signature:

const char* get_version();

My declaration is:

fun get_version(): LibC::Char*

And to use it:

version = MyLib.get_version()
puts version # how to convert to String?

How can I manage the return string? Do I have to import also strlen to measure the length of the C string and covert it to Crystal string manually?

Sacksen

Answer 1

You wrap the Char* pointer with String.new(MyLib.version). If you know the string length, you may call String.new(ptr, size) too.

Note that this will copy the data from the pointer, so the C binding may release its pointer without affecting the Crystal String.

Carthy

Also, one probably wants to delete the pointer manually, only in case the source expects caller to do. – Ihab