struct ara::core::hash

In module core, the template structure ara::core::hash serves as a generic function object for the deterministic calculation of hash values, as described in the specification for [bitset]. It provides a uniform interface through which input objects are converted into integer hash values for indexing in associative data structures via function calls. Since the structure is likely designed as a stateless function object, hash value calculations are free of side effects and can be executed concurrently without synchronization overhead. Question (open)

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Context

In module core of the AUTOSAR Adaptive Platform (release R25-11), the template structure ara::core::hash provides the standardized interface for generating hash codes. The formal declaration is template <class T> struct hash;. According to the specification description, the behavior is oriented towards the corresponding usage in [bitset]. In the system context, ara::core::hash presumably assumes the role of a standard-compliant function object following the pattern of std::hash, which provides data structures and algorithms with a consistent hash value for instances of type T. Question Q-c0770dd7d494f007 (open)

As a central utility, the structure typically interacts with associative data structures, hash tables, and generic algorithms. Predefined specializations for adaptive basic types, such as for bit sets, enable higher-level components to organize heterogeneous objects efficiently in hash-based lookup tables. The core responsibility of the structure lies in encapsulating the type-specific hash algorithm, allowing calling algorithms to operate independently of the concrete internal structure of the payload data type.

Lifecycle

The structure ara::core::hash has a functional character and does not exhibit a complex lifecycle. According to standard interpretation, instances of the template class manage no dynamic system resources and maintain no persistent internal states. Creation of a function object typically occurs ad hoc at the point of call via the default constructor or implicitly in the context of generic container classes.

Since instances of ara::core::hash are likely designed as stateless function objects, neither discrete operating phases nor explicit state transitions exist. Question Q-f8cb3f1f0979d453 (open) Destruction of an instance is trivial and requires no deallocation logic. The assumed statelessness also implies that parallel executions across multiple threads are inherently concurrent and thread-safe: Multiple execution threads can call the same functor or simultaneously created instances at the same time without synchronization mechanisms being required.

Usage Path

The typical sequence when using ara::core::hash is divided into the following steps:

• Type binding and instantiation: The caller instantiates the function object for the desired target type T or declares the structure as a hash functor in a higher-level template class.
• Passing the instance: The function object is invoked via its call operator with a const reference to the target object (for example, an instance of bitset).
• Processing the return value: The call deterministically returns an integer hash value, which is subsequently used to determine table indices or check values.

For user-defined data types, the template structure can be specialized to provide a specific calculation algorithm. Regardless of the type, for every conforming manifestation, identical hash values must be generated reproducibly for identical input values across the entire runtime.

Error Scenarios

Due to the deterministic nature of hash value calculations, no error codes or runtime error states occur with ara::core::hash. According to general design principles, the evaluation is likely designed as a no-throw operation. Question (open) Potential issues are limited to static design decisions and inherent properties of hashing methods:

• Missing type specialization: If ara::core::hash is used for a type for which no suitable specialization exists, this leads to an error during compile time.
• Hash collisions: The occurrence of identical hash values for different input values represents a mathematically unavoidable property. This is not an error of the function object, but a normal occurrence that the consuming data structure must handle through collision resolution.
• Preconditions and postconditions: A precondition for execution is the validity of the passed object reference value; a postcondition is the provision of a stable hash value.