Can We Enhance the Reusability of Key-Oriented Access Protection in C ?

Can we improve the reusability of the key-oriented access protection pattern?

The provided pattern utilizes friend classes to control access to methods, granting access to only those who possess specific keys. While effective, this approach can become cumbersome due to the repetition of friend declarations and the need to specify passkeys within the method's parameter list.

Solution in C 03:

In C 03, a macro-based approach can enhance usability by reducing the number of friend declarations and allowing the creation of passkeys outside the method's definition. Macros are used to define passkeys that can be easily generated for different friend classes, simplifying the code and making it easier to maintain. This solution, however, comes with limitations such as the requirement to know specific passkey names and the presence of a block of passkey definitions, which can be perceived as ungainly.

Solution in C 0x:

C 0x introduces significant enhancements that enable a cleaner and more expressive implementation of the pattern.

• Variadic templates: Passkeys are templated on their parameter types, allowing for key types to be specified as variadic template parameters. This eliminates the need for macros when defining functions that require passkeys.
• Template parameters as friends: Templates can now be befriended, which enables the direct specification of passkeys as template parameters within the methods they protect. This eliminates the need to declare passkeys separately and simplifies the process of creating and using them.

The implementation in C 0x involves defining a passkey template that represents unique passkeys for each class and a allow template that checks if a passkey is allowed for a particular function, based on the template parameters of that function. This approach offers significant benefits:

• Passkeys are specific to each class: Each class possesses its unique passkey, which can be used to grant or restrict access.
• Simplified function access: Functions are befriended using the allow template, which ensures that only those who possess the required passkeys can invoke the function.
• Generic and reusable: This solution is generic and can be applied to any combination of classes and functions without requiring special definitions, making it highly reusable and easy to incorporate into existing codebases.

The above is the detailed content of Can We Enhance the Reusability of Key-Oriented Access Protection in C ?. For more information, please follow other related articles on the PHP Chinese website!