CODEWITHSUNDEEP
c++boostshared-ptr
Component 10
Component 10

Reputation: 10477

C++ / Boost shared resource class for managing resource lifecycle like shared_ptr

Does Boost, or anything else, contain a container will act like a shared pointer but allow me to control what happens to the shared 'resource' at the end of it's life? I want to encapsulate an object that can be handed around but, when no longer needed can be closed in a context defined way.

For example, I might want to create and pass around a file handle knowing that when it goes out of scope, the file will be closed automatically, but I don't want to delete the handle.

I could implement it myself, but would rather not get into that if the framework already exists - someone has no doubt done it better. I can't use boost::shared_ptr, at least not in it's normal form, as the resource should not be deleted at end of life.

Upvotes: 3

Views: 744

Answers (3)

Jagannath
Jagannath

Reputation: 4025

Since you can't use Boost or the std::shared_ptr, you could write a smart pointer be it shared or unique that has custom Deleter.

Upvotes: 1

Rook
Rook

Reputation: 6145

Are you aware that std::shared_ptr can take a custom deleter class? This need not actually use "delete" or "free", but could easily use some other sort of mechanism (such as a reference counting mechanism's release and so on).

Here's a dead simple example for you:

std::shared_ptr<FILE> foo(fopen("la", "r"), fclose);

The deleter just needs to be a function that takes the pointer type that the shared_ptr wraps. In this case, whenfoo goes out of scope, shared_ptr will close the file for you. (Note: this isn't a totally sensible implementation, because no error values are checked. It is just an example).

Upvotes: 8

pstrjds
pstrjds

Reputation: 17428

If you are using a compiler that supports the C++11 std::shared_ptr, one of the constructors takes a custom "deleter" function. This would allow you to write your own function for "releasing" the resources.

EDIT - I forgot that std::shared_ptr was actually in the TR1 update to C++, so if your compiler supports TR1 you should be in good shape.

Upvotes: 3

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