[vlc-devel] [PATCH 1/9] vlc_list: add a typedef vlc_list_node to clarify which is the list and which is the node
Steve Lhomme
robux4 at ycbcr.xyz
Mon Aug 20 12:44:11 CEST 2018
On 20/08/2018 12:03, Rémi Denis-Courmont wrote:
> 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.
I think you're talking about the type. I didn't look too much into the
implementation (because one shouldn't). But for the elements where the
list is stored and where the elements are it does make a difference at
least for the reader.
The vlc_list also doesn't say that it's circular. So it seems the intent
was not to tell about implementation details. So I don't see why the
user should have to know they're interchangeable (maybe one day they won't).
> 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...
Agree to disagree.
>
> 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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> excuser ma brièveté.
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