Hello!

On Thu, Jan 16, 2014 at 02:04:45AM -0500, microwish wrote:

> Hello there,
>
> code snippet in the definition of ngx_chain_add_copy in ngx_buf.c:
>
>
> ll = chain;
>
>
>
> for (cl = *chain; cl; cl = cl->next) {
> ll = &cl->next;
> }
>
>
> Why is ll assigned repeatedly? I'm sorry for failed thinking out any
> necessity.
>
> And I modified the above as the following. Is it OK?
>
>
> if (*chain) {
> for (cl = *chain; cl->next; cl = cl->next) { /* void */ }
> ll = &cl->next;
> } else {
> ll = chain;
> }
>
>
> Thank you very much.

The code snippets look equivalent from logical point of view.
From performance point of view - they are mostly equivalent too,
as cl->next address anyway needs to be loaded on each cycle
iteration and will be available in a register, so assignment is
essentially a nop. The code currently used is shorter though, and
easier to read.

--
Maxim Dounin
http://nginx.org/

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