75 lines
2.6 KiB
C
75 lines
2.6 KiB
C
/*
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* This file is part of libooc.
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* https://xw3.org/hanez/libooc
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*
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* Copyright 2026 Johannes Findeisen <you@hanez.org>
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* Licensed under the terms of the Apache-2.0 license.
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* https://opensource.org/license/apache-2-0
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*/
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#ifndef DOG_H
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#define DOG_H
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#include "animal.h"
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typedef struct Dog Dog;
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/*
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* Derived class.
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*
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* The embedded Animal comes first, so a Dog pointer can be handed to any
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* function expecting an Animal, and Dog adds a breed of its own.
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*
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* Two things follow from that ordering. The ooc_object header inside Animal
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* stays at offset zero, where the library looks for it, and the upcast is a
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* no-op cast because both addresses are the same -- which is what lets speak()
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* in dog.c cast its Animal * back to a Dog * without arithmetic. The cost is
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* that a Dog may not add a member of its own before the base.
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*
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* The struct holds no destructor of its own; the one Dog registers lives in
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* Dog_class and releases both the breed and Animal's name.
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*/
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struct Dog {
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Animal animal;
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char *breed;
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};
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/*
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* Dog's runtime type record, the value ooc_new() takes.
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*
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* Its `super` is Animal_class, so a Dog inherits Animal's fields, and its
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* `size` is sizeof(Dog), so the allocation has room for the breed.
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*/
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extern const ooc_class Dog_class;
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/*
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* Create a Dog named `name` of the given `breed` and return it, or NULL.
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*
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* The result has a reference count of one, so ownership is the caller's and it
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* must reach ooc_release() eventually. Returns NULL if any step of the
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* construction fails, leaving nothing to release.
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*
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* The object is a Dog and answers to Dog's `speak`, whether it is later reached
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* through a Dog * or an Animal *.
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*/
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Dog *dog_new(const char *name, int age, const char *breed);
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/*
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* Initialise the members Dog owns, so a subclass constructor can build the Dog
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* part of a larger object instead of duplicating it.
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*
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* This is the second link in the chain of constructors below Animal: a subclass
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* of Dog calls this, gets Dog's vtable installed, and then overwrites the
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* vtable with its own the same way dog_new() does.
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*
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* The caller supplies storage that ooc_new() has already allocated and
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* zeroed. On failure the object is left exactly as it was found, so the caller
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* may release it without a destructor having anything to do.
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*
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* Returns 0, or -1 for a NULL dog, an already initialised one, or a failed copy
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* of the breed. Requires zero-initialised members and external synchronization
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* between constructors in different threads.
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*/
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int dog_init(Dog *dog, const char *name, int age, const char *breed);
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#endif /* DOG_H */
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