[vlc-devel] [PATCH 1/9] vlc_list: add a typedef vlc_list_node to clarify which is the list and which is the node
Rémi Denis-Courmont
remi at remlab.net
Mon Aug 20 12:03:53 CEST 2018
No, it is not possible to distinguish the type of a node and a head in a circular list, in a statically typed (only) language. You need dynamic typing for that to work.
Adding two different type names for the same thing is confusing. This patch series makes things much more confusing, or rather confused even, to me. And I happen to be the author...
Le 20 août 2018 10:21:38 GMT+03:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>On 17/08/2018 19:06, Rémi Denis-Courmont wrote:
>> You cannot have a different typedef here. This is by design. And we
>> already use different member names for heads and nodes.
>
>It's possible, it's even desirable. "vlc_list node" is the part that
>doesn't make sense here. A node is not a list, the fact it shares the
>same internals is because of the current design. It may change in the
>future, but what is 100% is that a node must not be used as a vlc_list
>despite its type. And so it should not imply it can be from its type
>(maybe the mnemonic is wrong, who knows).
>
>>
>> Le 17 août 2018 16:04:33 GMT+03:00, Steve Lhomme <robux4 at ycbcr.xyz> a
>
>> écrit :
>>
>> ---
>> include/vlc_list.h | 23 +++++++++++++----------
>> 1 file changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/vlc_list.h b/include/vlc_list.h
>> index 45263cc789..002119db6b 100644
>> --- a/include/vlc_list.h
>> +++ b/include/vlc_list.h
>> @@ -45,6 +45,9 @@ struct vlc_list
>> struct vlc_list *next;
>> };
>>
>> +/* type to use in list items to differentiate with the list
>itself */
>> +typedef struct vlc_list vlc_list_node;
>> +
>> /**
>> * Static initializer for a list head.
>> */
>> @@ -66,7 +69,7 @@ static inline void vlc_list_init(struct
>vlc_list *restrict head)
>> * \param prev Node pointer of the previous element.
>> * \param next Node pointer of the next element.
>> */
>> -static inline void vlc_list_add_between(struct vlc_list
>*restrict node,
>> +static inline void vlc_list_add_between(vlc_list_node *restrict
>node,
>> struct vlc_list *prev,
>> struct vlc_list *next)
>> {
>> @@ -82,7 +85,7 @@ static inline void vlc_list_add_between(struct
>vlc_list *restrict node,
>> * \param node Node pointer of the element to insert [OUT].
>> * \param prev Node pointer of the previous element.
>> */
>> -static inline void vlc_list_add_after(struct vlc_list *restrict
>node,
>> +static inline void vlc_list_add_after(vlc_list_node *restrict
>node,
>> struct vlc_list *prev)
>> {
>> vlc_list_add_between(node, prev, prev->next);
>> @@ -94,7 +97,7 @@ static inline void vlc_list_add_after(struct
>vlc_list *restrict node,
>> * \param node Node pointer of the element to insert [OUT].
>> * \param prev Node pointer of the next element.
>> */
>> -static inline void vlc_list_add_before(struct vlc_list *restrict
>node,
>> +static inline void vlc_list_add_before(vlc_list_node *restrict
>node,
>> struct vlc_list *next)
>> {
>> vlc_list_add_between(node, next->prev, next);
>> @@ -106,7 +109,7 @@ static inline void vlc_list_add_before(struct
>vlc_list *restrict node,
>> * \param node Node pointer of the element to append to the
>list [OUT].
>> * \param head Head pointer of the list to append the element
>to.
>> */
>> -static inline void vlc_list_append(struct vlc_list *restrict
>node,
>> +static inline void vlc_list_append(vlc_list_node *restrict node,
>> struct vlc_list *head)
>> {
>> vlc_list_add_before(node, head);
>> @@ -118,7 +121,7 @@ static inline void vlc_list_append(struct
>vlc_list *restrict node,
>> * \param node Node pointer of the element to prepend to the
>list [OUT].
>> * \param head Head pointer of the list to prepend the element
>to.
>> */
>> -static inline void vlc_list_prepend(struct vlc_list *restrict
>node,
>> +static inline void vlc_list_prepend(vlc_list_node *restrict
>node,
>> struct vlc_list *head)
>> {
>> vlc_list_add_after(node, head);
>> @@ -131,7 +134,7 @@ static inline void vlc_list_prepend(struct
>vlc_list *restrict node,
>> * \warning The element must be inside a list.
>> * Otherwise the behaviour is undefined.
>> */
>> -static inline void vlc_list_remove(struct vlc_list *restrict
>node)
>> +static inline void vlc_list_remove(vlc_list_node *restrict node)
>> {
>> struct vlc_list *prev = node->prev;
>> struct vlc_list *next = node->next;
>> @@ -177,7 +180,7 @@ static inline bool vlc_list_is_empty(const
>struct vlc_list *head)
>> * \retval false The element is not first (or is in another
>list).
>> * \retval true The element is first.
>> */
>> -static inline bool vlc_list_is_first(const struct vlc_list
>*node,
>> +static inline bool vlc_list_is_first(const vlc_list_node *node,
>> const struct vlc_list
>*head)
>> {
>> return node->prev == head;
>> @@ -192,7 +195,7 @@ static inline bool vlc_list_is_first(const
>struct vlc_list *node,
>> * \retval false The element is not last (or is in another
>list).
>> * \retval true The element is last.
>> */
>> -static inline bool vlc_list_is_last(const struct vlc_list *node,
>> +static inline bool vlc_list_is_last(const vlc_list_node *node,
>> const struct vlc_list
>*head)
>> {
>> return node->next == head;
>> @@ -289,7 +292,7 @@ static inline void
>*vlc_list_last_or_null(const struct vlc_list *head,
>> }
>>
>> static inline void *vlc_list_prev_or_null(const struct vlc_list
>*head,
>> - struct vlc_list *node,
>> + vlc_list_node *node,
>> size_t offset)
>> {
>> if (vlc_list_is_first(node, head))
>> @@ -298,7 +301,7 @@ static inline void
>*vlc_list_prev_or_null(const struct vlc_list *head,
>> }
>>
>> static inline void *vlc_list_next_or_null(const struct vlc_list
>*head,
>> - struct vlc_list *node,
>> + vlc_list_node *node,
>> size_t offset)
>> {
>> if (vlc_list_is_last(node, head))
>>
>>
>> --
>> Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez
>> excuser ma brièveté.
>>
>>
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Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.
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