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

[Max Reitz <mreitz@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 3195 bytes --]

On 2017-06-19 15:55, Kevin Wolf wrote:
> 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.

Yes, I'll add a comment.

>> + */
>> +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.

That's why I'm checking that x and y have the same size before.

>> +/**
>>   * 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.

Yes, I'll add a comment here, too.

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

Of course it does because lists are not sets but arrays (in contrast to
dicts).

Max

>> + */
>> +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
> 



[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 498 bytes --]