Remainder of "Simplify qobject refcount"

[Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Marc-André Lureau 7 years, 2 months ago

Add a new function qdict_steal(), that deletes a key from a dict, and
returns the associated value, if any. Simplify related code.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/qapi/qmp/qdict.h |  1 +
 monitor.c                |  3 +--
 qobject/block-qdict.c    |  7 ++-----
 qobject/qdict.c          | 22 ++++++++++++++++++++++
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
index 7f3ec10a10..84644bfba6 100644
--- a/include/qapi/qmp/qdict.h
+++ b/include/qapi/qmp/qdict.h
@@ -37,6 +37,7 @@ QObject *qdict_entry_value(const QDictEntry *entry);
 size_t qdict_size(const QDict *qdict);
 void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
 void qdict_del(QDict *qdict, const char *key);
+QObject *qdict_steal(QDict *qdict, const char *key);
 int qdict_haskey(const QDict *qdict, const char *key);
 QObject *qdict_get(const QDict *qdict, const char *key);
 bool qdict_is_equal(const QObject *x, const QObject *y);
diff --git a/monitor.c b/monitor.c
index a1999e396c..eab2dc7b7b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4262,8 +4262,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
 
     qdict = qobject_to(QDict, req);
     if (qdict) {
-        id = qobject_ref(qdict_get(qdict, "id"));
-        qdict_del(qdict, "id");
+        id = qdict_steal(qdict, "id");
     } /* else will fail qmp_dispatch() */
 
     if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
index 42054cc274..a07664ee6a 100644
--- a/qobject/block-qdict.c
+++ b/qobject/block-qdict.c
@@ -692,8 +692,6 @@ void qdict_join(QDict *dest, QDict *src, bool overwrite)
  */
 bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
 {
-    QObject *qobj;
-
     while (renames->from) {
         if (qdict_haskey(qdict, renames->from)) {
             if (qdict_haskey(qdict, renames->to)) {
@@ -702,9 +700,8 @@ bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
                 return false;
             }
 
-            qobj = qdict_get(qdict, renames->from);
-            qdict_put_obj(qdict, renames->to, qobject_ref(qobj));
-            qdict_del(qdict, renames->from);
+            qdict_put_obj(qdict, renames->to,
+                          qdict_steal(qdict, renames->from));
         }
 
         renames++;
diff --git a/qobject/qdict.c b/qobject/qdict.c
index 3d8c2f7bbc..322f23f094 100644
--- a/qobject/qdict.c
+++ b/qobject/qdict.c
@@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
     }
 }
 
+/**
+ * qdict_steal(): Steal a 'key:value' pair from the dictionary
+ *
+ * Return the associated entry value and remove it, or NULL.
+ */
+QObject *qdict_steal(QDict *qdict, const char *key)
+{
+    QDictEntry *entry;
+    QObject *val = NULL;
+
+    entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
+    if (entry) {
+        QLIST_REMOVE(entry, next);
+        val = qobject_ref(entry->value);
+        qentry_destroy(entry);
+        qdict->size--;
+    }
+
+    return val;
+}
+
+
 /**
  * qdict_is_equal(): Test whether the two QDicts are equal
  *
-- 
2.18.0.547.g1d89318c48

Re: [Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Markus Armbruster 7 years, 2 months ago

Marc-André Lureau <marcandre.lureau@redhat.com> writes:

> Add a new function qdict_steal(), that deletes a key from a dict, and
> returns the associated value, if any. Simplify related code.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  include/qapi/qmp/qdict.h |  1 +
>  monitor.c                |  3 +--
>  qobject/block-qdict.c    |  7 ++-----
>  qobject/qdict.c          | 22 ++++++++++++++++++++++
>  4 files changed, 26 insertions(+), 7 deletions(-)

Missing: tests/check-qdict.c update.

> diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
> index 7f3ec10a10..84644bfba6 100644
> --- a/include/qapi/qmp/qdict.h
> +++ b/include/qapi/qmp/qdict.h
> @@ -37,6 +37,7 @@ QObject *qdict_entry_value(const QDictEntry *entry);
>  size_t qdict_size(const QDict *qdict);
>  void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
>  void qdict_del(QDict *qdict, const char *key);
> +QObject *qdict_steal(QDict *qdict, const char *key);
>  int qdict_haskey(const QDict *qdict, const char *key);
>  QObject *qdict_get(const QDict *qdict, const char *key);
>  bool qdict_is_equal(const QObject *x, const QObject *y);
> diff --git a/monitor.c b/monitor.c
> index a1999e396c..eab2dc7b7b 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -4262,8 +4262,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
>  
>      qdict = qobject_to(QDict, req);
>      if (qdict) {
> -        id = qobject_ref(qdict_get(qdict, "id"));
> -        qdict_del(qdict, "id");
> +        id = qdict_steal(qdict, "id");
>      } /* else will fail qmp_dispatch() */
>  
>      if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
> diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
> index 42054cc274..a07664ee6a 100644
> --- a/qobject/block-qdict.c
> +++ b/qobject/block-qdict.c
> @@ -692,8 +692,6 @@ void qdict_join(QDict *dest, QDict *src, bool overwrite)
>   */
>  bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
>  {
> -    QObject *qobj;
> -
>      while (renames->from) {
>          if (qdict_haskey(qdict, renames->from)) {
>              if (qdict_haskey(qdict, renames->to)) {
> @@ -702,9 +700,8 @@ bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
>                  return false;
>              }
>  
> -            qobj = qdict_get(qdict, renames->from);
> -            qdict_put_obj(qdict, renames->to, qobject_ref(qobj));
> -            qdict_del(qdict, renames->from);
> +            qdict_put_obj(qdict, renames->to,
> +                          qdict_steal(qdict, renames->from));
>          }
>  
>          renames++;

How did you find possible uses for qdict_steal()?

> diff --git a/qobject/qdict.c b/qobject/qdict.c
> index 3d8c2f7bbc..322f23f094 100644
> --- a/qobject/qdict.c
> +++ b/qobject/qdict.c
> @@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
>      }
>  }
>  
> +/**
> + * qdict_steal(): Steal a 'key:value' pair from the dictionary

"Steal" is cute, but perhaps qdict_get_and_del() would be clearer.

> + *
> + * Return the associated entry value and remove it, or NULL.

Suggest

    * If @qdict has @key, return its value, and delete it from @qdict.
    * Else, return NULL.

> + */
> +QObject *qdict_steal(QDict *qdict, const char *key)
> +{
> +    QDictEntry *entry;
> +    QObject *val = NULL;
> +
> +    entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
> +    if (entry) {
> +        QLIST_REMOVE(entry, next);
> +        val = qobject_ref(entry->value);
> +        qentry_destroy(entry);
> +        qdict->size--;
> +    }
> +
> +    return val;
> +}

This is a slightly extended qdict_del().

   void qdict_del(QDict *qdict, const char *key)
   {
       QDictEntry *entry;

       entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
       if (entry) {
           QLIST_REMOVE(entry, next);
           qentry_destroy(entry);
           qdict->size--;
       }
   }

Heavy-handed de-duplication:

   QObject *qdict_get_and_del(QDict *qdict, const char *key)
   {
       QDictEntry *entry;
       QObject *val;

       entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
       if (!entry) {
           return NULL;
       }

       QLIST_REMOVE(entry, next);
       val = qobject_ref(entry->value);
       qentry_destroy(entry);
       qdict->size--;
       return val;
   }

   void qdict_del(QDict *qdict, const char *key)
   {
       qobject_unref(qdict_get_and_del(qdict, key));
   }

Makes qdict_del() execute an additional qobject_ref() / qobject_unref(),
but that shouldn't matter.

> +
> +

Just one blank line, please.

>  /**
>   * qdict_is_equal(): Test whether the two QDicts are equal
>   *

Re: [Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Marc-André Lureau 7 years, 2 months ago

Hi

On Fri, Aug 24, 2018 at 10:05 AM Markus Armbruster <armbru@redhat.com> wrote:
>
> Marc-André Lureau <marcandre.lureau@redhat.com> writes:
>
> > Add a new function qdict_steal(), that deletes a key from a dict, and
> > returns the associated value, if any. Simplify related code.
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  include/qapi/qmp/qdict.h |  1 +
> >  monitor.c                |  3 +--
> >  qobject/block-qdict.c    |  7 ++-----
> >  qobject/qdict.c          | 22 ++++++++++++++++++++++
> >  4 files changed, 26 insertions(+), 7 deletions(-)
>
> Missing: tests/check-qdict.c update.

ok

>
> > diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
> > index 7f3ec10a10..84644bfba6 100644
> > --- a/include/qapi/qmp/qdict.h
> > +++ b/include/qapi/qmp/qdict.h
> > @@ -37,6 +37,7 @@ QObject *qdict_entry_value(const QDictEntry *entry);
> >  size_t qdict_size(const QDict *qdict);
> >  void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
> >  void qdict_del(QDict *qdict, const char *key);
> > +QObject *qdict_steal(QDict *qdict, const char *key);
> >  int qdict_haskey(const QDict *qdict, const char *key);
> >  QObject *qdict_get(const QDict *qdict, const char *key);
> >  bool qdict_is_equal(const QObject *x, const QObject *y);
> > diff --git a/monitor.c b/monitor.c
> > index a1999e396c..eab2dc7b7b 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -4262,8 +4262,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
> >
> >      qdict = qobject_to(QDict, req);
> >      if (qdict) {
> > -        id = qobject_ref(qdict_get(qdict, "id"));
> > -        qdict_del(qdict, "id");
> > +        id = qdict_steal(qdict, "id");
> >      } /* else will fail qmp_dispatch() */
> >
> >      if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
> > diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
> > index 42054cc274..a07664ee6a 100644
> > --- a/qobject/block-qdict.c
> > +++ b/qobject/block-qdict.c
> > @@ -692,8 +692,6 @@ void qdict_join(QDict *dest, QDict *src, bool overwrite)
> >   */
> >  bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
> >  {
> > -    QObject *qobj;
> > -
> >      while (renames->from) {
> >          if (qdict_haskey(qdict, renames->from)) {
> >              if (qdict_haskey(qdict, renames->to)) {
> > @@ -702,9 +700,8 @@ bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
> >                  return false;
> >              }
> >
> > -            qobj = qdict_get(qdict, renames->from);
> > -            qdict_put_obj(qdict, renames->to, qobject_ref(qobj));
> > -            qdict_del(qdict, renames->from);
> > +            qdict_put_obj(qdict, renames->to,
> > +                          qdict_steal(qdict, renames->from));
> >          }
> >
> >          renames++;
>
> How did you find possible uses for qdict_steal()?

manual review

>
> > diff --git a/qobject/qdict.c b/qobject/qdict.c
> > index 3d8c2f7bbc..322f23f094 100644
> > --- a/qobject/qdict.c
> > +++ b/qobject/qdict.c
> > @@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
> >      }
> >  }
> >
> > +/**
> > + * qdict_steal(): Steal a 'key:value' pair from the dictionary
>
> "Steal" is cute, but perhaps qdict_get_and_del() would be clearer.

"steal" is common in glib. I don't mind renaming.

>
> > + *
> > + * Return the associated entry value and remove it, or NULL.
>
> Suggest
>
>     * If @qdict has @key, return its value, and delete it from @qdict.
>     * Else, return NULL.
>
> > + */
> > +QObject *qdict_steal(QDict *qdict, const char *key)
> > +{
> > +    QDictEntry *entry;
> > +    QObject *val = NULL;
> > +
> > +    entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
> > +    if (entry) {
> > +        QLIST_REMOVE(entry, next);
> > +        val = qobject_ref(entry->value);
> > +        qentry_destroy(entry);
> > +        qdict->size--;
> > +    }
> > +
> > +    return val;
> > +}
>
> This is a slightly extended qdict_del().
>
>    void qdict_del(QDict *qdict, const char *key)
>    {
>        QDictEntry *entry;
>
>        entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
>        if (entry) {
>            QLIST_REMOVE(entry, next);
>            qentry_destroy(entry);
>            qdict->size--;
>        }
>    }
>
> Heavy-handed de-duplication:
>
>    QObject *qdict_get_and_del(QDict *qdict, const char *key)
>    {
>        QDictEntry *entry;
>        QObject *val;
>
>        entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
>        if (!entry) {
>            return NULL;
>        }
>
>        QLIST_REMOVE(entry, next);
>        val = qobject_ref(entry->value);
>        qentry_destroy(entry);
>        qdict->size--;
>        return val;
>    }
>
>    void qdict_del(QDict *qdict, const char *key)
>    {
>        qobject_unref(qdict_get_and_del(qdict, key));
>    }
>
> Makes qdict_del() execute an additional qobject_ref() / qobject_unref(),
> but that shouldn't matter.

ok

>
> > +
> > +
>
> Just one blank line, please.

ok

>
> >  /**
> >   * qdict_is_equal(): Test whether the two QDicts are equal
> >   *
>

thanks

-- 
Marc-André Lureau

Re: [Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Markus Armbruster 7 years, 2 months ago

Marc-André Lureau <marcandre.lureau@gmail.com> writes:

> Hi
>
> On Fri, Aug 24, 2018 at 10:05 AM Markus Armbruster <armbru@redhat.com> wrote:
>>
>> Marc-André Lureau <marcandre.lureau@redhat.com> writes:
>>
>> > Add a new function qdict_steal(), that deletes a key from a dict, and
>> > returns the associated value, if any. Simplify related code.
>> >
>> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>> > ---
>> >  include/qapi/qmp/qdict.h |  1 +
>> >  monitor.c                |  3 +--
>> >  qobject/block-qdict.c    |  7 ++-----
>> >  qobject/qdict.c          | 22 ++++++++++++++++++++++
>> >  4 files changed, 26 insertions(+), 7 deletions(-)
>>
>> Missing: tests/check-qdict.c update.
>
> ok
>
>>
>> > diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
>> > index 7f3ec10a10..84644bfba6 100644
>> > --- a/include/qapi/qmp/qdict.h
>> > +++ b/include/qapi/qmp/qdict.h
>> > @@ -37,6 +37,7 @@ QObject *qdict_entry_value(const QDictEntry *entry);
>> >  size_t qdict_size(const QDict *qdict);
>> >  void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
>> >  void qdict_del(QDict *qdict, const char *key);
>> > +QObject *qdict_steal(QDict *qdict, const char *key);
>> >  int qdict_haskey(const QDict *qdict, const char *key);
>> >  QObject *qdict_get(const QDict *qdict, const char *key);
>> >  bool qdict_is_equal(const QObject *x, const QObject *y);
>> > diff --git a/monitor.c b/monitor.c
>> > index a1999e396c..eab2dc7b7b 100644
>> > --- a/monitor.c
>> > +++ b/monitor.c
>> > @@ -4262,8 +4262,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
>> >
>> >      qdict = qobject_to(QDict, req);
>> >      if (qdict) {
>> > -        id = qobject_ref(qdict_get(qdict, "id"));
>> > -        qdict_del(qdict, "id");
>> > +        id = qdict_steal(qdict, "id");
>> >      } /* else will fail qmp_dispatch() */
>> >
>> >      if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
>> > diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
>> > index 42054cc274..a07664ee6a 100644
>> > --- a/qobject/block-qdict.c
>> > +++ b/qobject/block-qdict.c
>> > @@ -692,8 +692,6 @@ void qdict_join(QDict *dest, QDict *src, bool overwrite)
>> >   */
>> >  bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
>> >  {
>> > -    QObject *qobj;
>> > -
>> >      while (renames->from) {
>> >          if (qdict_haskey(qdict, renames->from)) {
>> >              if (qdict_haskey(qdict, renames->to)) {
>> > @@ -702,9 +700,8 @@ bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
>> >                  return false;
>> >              }
>> >
>> > -            qobj = qdict_get(qdict, renames->from);
>> > -            qdict_put_obj(qdict, renames->to, qobject_ref(qobj));
>> > -            qdict_del(qdict, renames->from);
>> > +            qdict_put_obj(qdict, renames->to,
>> > +                          qdict_steal(qdict, renames->from));
>> >          }
>> >
>> >          renames++;
>>
>> How did you find possible uses for qdict_steal()?
>
> manual review

Okay.  I expected a few more than two.

>> > diff --git a/qobject/qdict.c b/qobject/qdict.c
>> > index 3d8c2f7bbc..322f23f094 100644
>> > --- a/qobject/qdict.c
>> > +++ b/qobject/qdict.c
>> > @@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
>> >      }
>> >  }
>> >
>> > +/**
>> > + * qdict_steal(): Steal a 'key:value' pair from the dictionary
>>
>> "Steal" is cute, but perhaps qdict_get_and_del() would be clearer.
>
> "steal" is common in glib. I don't mind renaming.

Hmm.  I found g_hash_table_steal(), but it's a bit different: it
"Removes a key and its associated value from a GHashTable without
calling the key and value destroy functions" (that part seems close
enough), but returns a bool rather than the value.  Feels like sub-par
design to me.  Is this the precedence you have in mind?

[...]

Re: [Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Marc-André Lureau 7 years, 2 months ago

Hi
On Fri, Aug 24, 2018 at 1:30 PM Markus Armbruster <armbru@redhat.com> wrote:
>
> Marc-André Lureau <marcandre.lureau@gmail.com> writes:
>
> > Hi
> >
> > On Fri, Aug 24, 2018 at 10:05 AM Markus Armbruster <armbru@redhat.com> wrote:
> >>
> >> Marc-André Lureau <marcandre.lureau@redhat.com> writes:
> >>
> >> > Add a new function qdict_steal(), that deletes a key from a dict, and
> >> > returns the associated value, if any. Simplify related code.
> >> >
> >> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> >> > ---
> >> >  include/qapi/qmp/qdict.h |  1 +
> >> >  monitor.c                |  3 +--
> >> >  qobject/block-qdict.c    |  7 ++-----
> >> >  qobject/qdict.c          | 22 ++++++++++++++++++++++
> >> >  4 files changed, 26 insertions(+), 7 deletions(-)
> >>
> >> Missing: tests/check-qdict.c update.
> >
> > ok
> >
> >>
> >> > diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
> >> > index 7f3ec10a10..84644bfba6 100644
> >> > --- a/include/qapi/qmp/qdict.h
> >> > +++ b/include/qapi/qmp/qdict.h
> >> > @@ -37,6 +37,7 @@ QObject *qdict_entry_value(const QDictEntry *entry);
> >> >  size_t qdict_size(const QDict *qdict);
> >> >  void qdict_put_obj(QDict *qdict, const char *key, QObject *value);
> >> >  void qdict_del(QDict *qdict, const char *key);
> >> > +QObject *qdict_steal(QDict *qdict, const char *key);
> >> >  int qdict_haskey(const QDict *qdict, const char *key);
> >> >  QObject *qdict_get(const QDict *qdict, const char *key);
> >> >  bool qdict_is_equal(const QObject *x, const QObject *y);
> >> > diff --git a/monitor.c b/monitor.c
> >> > index a1999e396c..eab2dc7b7b 100644
> >> > --- a/monitor.c
> >> > +++ b/monitor.c
> >> > @@ -4262,8 +4262,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
> >> >
> >> >      qdict = qobject_to(QDict, req);
> >> >      if (qdict) {
> >> > -        id = qobject_ref(qdict_get(qdict, "id"));
> >> > -        qdict_del(qdict, "id");
> >> > +        id = qdict_steal(qdict, "id");
> >> >      } /* else will fail qmp_dispatch() */
> >> >
> >> >      if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
> >> > diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
> >> > index 42054cc274..a07664ee6a 100644
> >> > --- a/qobject/block-qdict.c
> >> > +++ b/qobject/block-qdict.c
> >> > @@ -692,8 +692,6 @@ void qdict_join(QDict *dest, QDict *src, bool overwrite)
> >> >   */
> >> >  bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
> >> >  {
> >> > -    QObject *qobj;
> >> > -
> >> >      while (renames->from) {
> >> >          if (qdict_haskey(qdict, renames->from)) {
> >> >              if (qdict_haskey(qdict, renames->to)) {
> >> > @@ -702,9 +700,8 @@ bool qdict_rename_keys(QDict *qdict, const QDictRenames *renames, Error **errp)
> >> >                  return false;
> >> >              }
> >> >
> >> > -            qobj = qdict_get(qdict, renames->from);
> >> > -            qdict_put_obj(qdict, renames->to, qobject_ref(qobj));
> >> > -            qdict_del(qdict, renames->from);
> >> > +            qdict_put_obj(qdict, renames->to,
> >> > +                          qdict_steal(qdict, renames->from));
> >> >          }
> >> >
> >> >          renames++;
> >>
> >> How did you find possible uses for qdict_steal()?
> >
> > manual review
>
> Okay.  I expected a few more than two.
>
> >> > diff --git a/qobject/qdict.c b/qobject/qdict.c
> >> > index 3d8c2f7bbc..322f23f094 100644
> >> > --- a/qobject/qdict.c
> >> > +++ b/qobject/qdict.c
> >> > @@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
> >> >      }
> >> >  }
> >> >
> >> > +/**
> >> > + * qdict_steal(): Steal a 'key:value' pair from the dictionary
> >>
> >> "Steal" is cute, but perhaps qdict_get_and_del() would be clearer.
> >
> > "steal" is common in glib. I don't mind renaming.
>
> Hmm.  I found g_hash_table_steal(), but it's a bit different: it
> "Removes a key and its associated value from a GHashTable without
> calling the key and value destroy functions" (that part seems close
> enough), but returns a bool rather than the value.  Feels like sub-par
> design to me.  Is this the precedence you have in mind?

They are many more _steal* functions in the GNOME libraries (search
with devhelp): the general idea is to remove an object from the owner
(without destrying), and return that object/reference.

-- 
Marc-André Lureau

Re: [Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()

Posted by Markus Armbruster 7 years, 2 months ago

Marc-André Lureau <marcandre.lureau@gmail.com> writes:

> Hi
> On Fri, Aug 24, 2018 at 1:30 PM Markus Armbruster <armbru@redhat.com> wrote:
>>
>> Marc-André Lureau <marcandre.lureau@gmail.com> writes:
>>
>> > Hi
>> >
>> > On Fri, Aug 24, 2018 at 10:05 AM Markus Armbruster <armbru@redhat.com> wrote:
>> >>
>> >> Marc-André Lureau <marcandre.lureau@redhat.com> writes:
[...]
>> >> > @@ -406,6 +406,28 @@ void qdict_del(QDict *qdict, const char *key)
>> >> >      }
>> >> >  }
>> >> >
>> >> > +/**
>> >> > + * qdict_steal(): Steal a 'key:value' pair from the dictionary
>> >>
>> >> "Steal" is cute, but perhaps qdict_get_and_del() would be clearer.
>> >
>> > "steal" is common in glib. I don't mind renaming.
>>
>> Hmm.  I found g_hash_table_steal(), but it's a bit different: it
>> "Removes a key and its associated value from a GHashTable without
>> calling the key and value destroy functions" (that part seems close
>> enough), but returns a bool rather than the value.  Feels like sub-par
>> design to me.  Is this the precedence you have in mind?
>
> They are many more _steal* functions in the GNOME libraries (search
> with devhelp): the general idea is to remove an object from the owner
> (without destrying), and return that object/reference.

Alright, I don't mind calling it "steal".

[Qemu-devel] [PATCH 1/2] qdict: add qdict_steal()
[Qemu-devel] [PATCH 2/2] qobject: modify qobject_ref() to assert on NULL