Re: std::string on "const char *"
On 21.01.2013 10:47, Jarek Blakarz wrote:
Hi
Consider the following program:
const char *str = "my name";
std::string s(str);
Can I do that ? If so, HOW ?
As the others suggested you need to write your own string class for this
purpose.
But if you want to go this way, I have some hints. (I have already done
this before.)
You will need *two* separate classes. One for ordinary strings and one
for compile time constant strings. The reason is quite easy: both accept
const char* as source for construction, but only one of them requires
that the lifetime of the storage behind the pointer exceeds the lifetime
of your string and maybe also copies of the string. C++11's constexpr
could be helpful.
Furthermore you need to decide whether you convert your constant string
to mutable strings at some place or if you modify you mutable string
class in a way that it does not free the storage of your constant
strings. The latter requires that length information and possibly a
reference count is not allocated in the same chunk of memory than the
string content. Fortunately this is common practice.
In fact you need a good reason to do all that, since it breaks
compatibility with std::string. Of course, you could provide a
conversion to std::string, but this would require a new allocation on
each conversion - a really bad idea.
In my case the reason was a C style plug-in interface that did not allow
dynamic allocations of storage that is shared between plug-in and main
program before an initialization function has been called.
Marcel