Re: [Qemu-devel] [PATCH 2/4] qapi: Add qobject_is_equal()

[Kevin Wolf <kwolf@redhat.com>]

Am 14.06.2017 um 17:31 hat Max Reitz geschrieben:
> This generic function (along with its implementations for different
> types) determines whether two QObjects are equal.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>

> diff --git a/qobject/qdict.c b/qobject/qdict.c
> index 88e2ecd..2ed57ca 100644
> --- a/qobject/qdict.c
> +++ b/qobject/qdict.c
> @@ -410,6 +410,30 @@ void qdict_del(QDict *qdict, const char *key)
>  }
>  
>  /**
> + * qdict_is_equal(): Tests whether the two QDicts are equal

This should specify what equality means for QDicts: Do their entries
have to point to the same objects, or is it enough if the objects
compare equal? It seems you're trying to implement the lattter.

> + */
> +bool qdict_is_equal(const QObject *x, const QObject *y)
> +{
> +    const QDict *dict_x = qobject_to_qdict(x), *dict_y = qobject_to_qdict(y);
> +    const QDictEntry *e;
> +
> +    if (qdict_size(dict_x) != qdict_size(dict_y)) {
> +        return false;
> +    }
> +
> +    for (e = qdict_first(dict_x); e; e = qdict_next(dict_x, e)) {
> +        const QObject *obj_x = qdict_entry_value(e);
> +        const QObject *obj_y = qdict_get(dict_y, qdict_entry_key(e));
> +
> +        if (!qobject_is_equal(obj_x, obj_y)) {
> +            return false;
> +        }
> +    }
> +
> +    return true;
> +}

If I'm not mistaken, this doesn't actually check equality, but that the
entries of x are a subset of the entries of y.

> +/**
>   * qdict_destroy_obj(): Free all the memory allocated by a QDict
>   */
>  void qdict_destroy_obj(QObject *obj)
> diff --git a/qobject/qlist.c b/qobject/qlist.c
> index 86b60cb..b3033c6 100644
> --- a/qobject/qlist.c
> +++ b/qobject/qlist.c
> @@ -140,6 +140,31 @@ QList *qobject_to_qlist(const QObject *obj)
>  }
>  
>  /**
> + * qlist_is_equal(): Tests whether the two QLists are equal

Like for QDict, this isn't a complete description.

Your implementation seems to check that both lists contain objects that
compare equal at each index (i.e. order matters).

> + */
> +bool qlist_is_equal(const QObject *x, const QObject *y)
> +{
> +    const QList *list_x = qobject_to_qlist(x), *list_y = qobject_to_qlist(y);
> +    const QListEntry *entry_x, *entry_y;
> +
> +    entry_x = qlist_first(list_x);
> +    entry_y = qlist_first(list_y);
> +
> +    while (entry_x && entry_y) {
> +        if (!qobject_is_equal(qlist_entry_obj(entry_x),
> +                              qlist_entry_obj(entry_y)))
> +        {
> +            return false;
> +        }
> +
> +        entry_x = qlist_next(entry_x);
> +        entry_y = qlist_next(entry_y);
> +    }
> +
> +    return !entry_x && !entry_y;
> +}
> +
> +/**
>   * qlist_destroy_obj(): Free all the memory allocated by a QList
>   */

Kevin