Is it safe and correct to use an std::tr1::shared_ptr as in the sample code below, for the purpose of reference counting? (this is just a particular sample, the class can contain anything else (void*) instead of the FILE*)
class File
{
public:
File(const char* path, const char* mode) :
_refcount(new int(0))
{
this->_file = fopen(path, mode);
}
~File()
{
if (this->_refcount.unique())
{
if (this->_file != NULL)
{
fclose(this->_file);
}
}
}
int write(void* buff, size_t size)
{
fwrite(buff, size, 1, this->_file);
}
private:
FILE* _file;
std::tr1::shared_ptr<int> _refcount;
};
Consider instead using a shared_ptr<FILE>
with a custom deleter:
struct fclose_deleter
{
void operator()(FILE* f)
{
if (f)
{
std::fclose(f);
}
}
};
Then, your File
class is much simpler (and correcter):
class File
{
public:
File(const char* path, const char* mode)
: _file(std::fopen(path, mode), fclose_deleter())
{
}
int write(void const* buff, size_t size)
{
// You'll want to verify that _file.get() is valid, or you'll want to
// throw in the constructor if the call to 'std::fopen()' fails.
std::fwrite(buff, size, 1, _file.get());
}
private:
std::tr1::shared_ptr<FILE> _file;
};