memcpy() avoidance using decode(bufferlist)

[David Disseldorp <ddiss@suse.de>]

Hi,

A question regarding bufferlist usage:

I'm working on the cmpext librados C API, and want to decode the OSD
response directly into a (char *buf/size_t len) buffer provided by the
caller.

I figured this would be straightforward via:
  bl.push_back(buffer::create_static(buf, len));
  ...
  ::decode_nohead(iter.get_remaining(), bl, iter);

However, the decoded data doesn't make it into buf, unless an extra copy
occurs via:
  bl.copy(0, bl.length(), buf);

Any suggestions on a clean way to avoid the extra copy here?

Cheers, David