feature:added new API function ngx.resp.get_headers for getting all response headers

[cubicdaiya]

I felt like this feature on seeing #334.

[agentzh]

@cubicdaiya Thank you for the patch! It looks generally good in a quick peek. I'll try to review and merge this shortly.

[agentzh]

@cubicdaiya Sorry for the delay on my side! I've just reviewed your patch and made some changes:

1. It is better to allocate the lowcase_key buffer in the Lua GC to prevent in-request memory leaks in the NGINX request pools.
2. We should skip ngx_table_elt_t entries in r->headers_out.headers whose hash fields are 0. (I've also added a test case for this.)

Will you review and test my modified version of your patch below?

http://openresty.org/download/ngx-lua-resp_get_headers.patch

Thanks!

[cubicdaiya]

@agentzh Thank you for review and modification.

After your patch is applied, It seems to work fine in my environment.

[agentzh]

@cubicdaiya I'm also thinking about sharing the metatable between ngx.req.get_headers and ngx.resp.get_headers. What do you think?

[cubicdaiya]

@agentzh I think it's better. I have applied your patch and the changes for the above-described requirement. What do you think about my changes?

[agentzh]

@cubicdaiya Sorry I'm very busy with other things these days. I'll check out your latest changes in the next week :) Thanks!

[agentzh]

@cubicdaiya Already applied a slightly modified version of your patch to master.

Basically I removed the line-trailing spaces and redundant blank lines. I also fixed source lines exceeding 80 columns in your patch.

Thank you for your contribution!