[sheepdog] [PATCH v2 01/11] rbtree: make rb_for_each_entry and rb_for_each more generic

[MORITA Kazutaka]

At Sat, 14 Sep 2013 18:34:21 +0800,
Liu Yuan wrote:
> 
> This allows us to call rb_xxx helpers inside the rb_for_xx helpers.
> 
> Signed-off-by: Liu Yuan <namei.unix at gmail.com>
> ---
>  include/rbtree.h |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/rbtree.h b/include/rbtree.h
> index 92c5389..07b6fe6 100644
> --- a/include/rbtree.h
> +++ b/include/rbtree.h
> @@ -164,16 +164,16 @@ static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
>  /* Iterate over a rbtree safe against removal of rbnode */
>  #define rb_for_each(pos, root)					\
>  	pos = rb_first(root);					\
> -	for (struct rb_node *__n = rb_next(pos);		\
> -	     pos && ({ __n = rb_next(pos); 1; });		\
> -	     pos = __n)
> +	for (struct rb_node *__n1 = rb_next(pos);		\
> +	     pos && ({ __n1 = rb_next(pos); 1; });		\
> +	     pos = __n1)
>  
>  /* Iterate over a rbtree of given type safe against removal of rbnode */
>  #define rb_for_each_entry(pos, root, member)				\
> -	for (struct rb_node *__pos = rb_first(root), *__n;		\
> -	     __pos && ({ __n = rb_next(__pos); 1; }) &&			\
> +	for (struct rb_node *__pos = rb_first(root), *__n2;		\
> +	     __pos && ({ __n2 = rb_next(__pos); 1; }) &&		\
>  		     ({ pos =  rb_entry(__pos, typeof(*pos), member); 1; }); \
> -	     __pos = __n)
> +	     __pos = __n2)

Then, we have to introduce __n3, __n4, ... to call macros inside
rb_for_each_entry()?  I think we should use better name convention.
E.g. adding a prefix like "__rb_for_each_entry_n" is unlikely to cause
collision though it's a bit too long.

I'd suggest adding a line number to the variable.  The below macro
generates a dynamic variable name with a line number.

#define __LOCAL(var, line) __ ## var ## line
#define _LOCAL(var, line) __LOCAL(var, line)
#define LOCAL(var) _LOCAL(var, __LINE__)

Then rb_for_each_entry() would be as follows.

  for (struct rb_node *LOCAL(pos) = rb_first(root), *LOCAL(n);    \
       LOCAL(pos) && ({ LOCAL(n) = rb_next(LOCAL(pos)); 1; }) &&  \
               ({ pos =  rb_entry(LOCAL(pos), typeof(*pos), member); 1; }); \
       LOCAL(pos) = LOCAL(n))

This also allows us to use rb_for_each_entry() inside rb_for_each_entry().

Thanks,

Kazutaka