On 04/22/2016 09:53 AM, David Disseldorp wrote:
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
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Hi David,
The decode logic is appending data to the end of the given bufferlist,
which is why it's skipping over the buffer pointer that you provide.
Internally, buffer::list is allocating its own 'buffer::ptr
append_buffer' to batch these appends. This append_buffer is not
currently exposed by the interface, but if there was a way to provide
your own buffer::ptr from buffer::create_static(), you could
hypothetically use that to avoid the copy.
Casey
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