Fixes LIBZMQ-584

The get_credential () member function returns
credential for the last peer we received message for.
The idea is that this function is used to implement user-level API.

These were exposed to users, but have subsequently been removed as
sockopts. They are currently only being used by ZAP, so I've moved it to
a simpl function call (actually it's only used in one case even in that,
so there may be a further simplification possible there).

ZMQ_CONFLATE option is passed to pipepair() which creates a usual
ypipe_t or ypipe_conflate_t and plugs it into pipe_t under a common
abstract base.

Copyrights had become ads for Sustrik's corporate sponsors, going against the original
agreement to share copyrights with the community (that agreement was: one line stating
iMatix copyright + one reference to AUTHORS file). The proliferation of corporate ads
is also unfair to the many individual authors. I've removed ALL corporate title from
the source files so the copyright statements can now be centralized in AUTHORS and
source files can be properly updated on an annual basis.

Code as stands breaks shutdown process. It was a bugfix by Arthur to a
bad line which was testing for an impossible state - but afaics we do
actually want to flush in those states. It is possible I am wrong on
that though - if there are any shutdown issues introduced aroudn this
commit I would suggest further investigation around this flushing
behavior.

Static analysis says:
src\pipe.cpp(193): error V547: Expression is always false. Probably the '||' operator should be used here.

If flush() is called on a pipe whose state was
"terminated" or "double_terminated", the programmer's
intent was to return immediately. But in fact the
two conditions can never be true simultaneously, so
the early return never happens, and we may try to flush
a terminated pipe anyway.

Revert "Rebinding on reconnection to allow for the pipe blocking will set the event sink again, which will cause an assert to be triggered. I have modified that to allow for setting the same sink to be OK. I believe this should be ok - on termination, if a pipe hasn't reconnected, it would just attempt to be erased from the pipes list again, which is reasonable"

This reverts commit 1566091b.

Revert "Remove unnecessary extra test in pipe assertion - now we are terminating pipes we don't need to allow the case in which a pipe is rebound to the same sink"

This reverts commit 29f8d9ca.

Remove unnecessary extra test in pipe assertion - now we are terminating pipes we don't need to allow the case in which a pipe is rebound to the same sink

Rebinding on reconnection to allow for the pipe blocking will set the event sink again, which will cause an assert to be triggered. I have modified that to allow for setting the same sink to be OK. I believe this should be ok - on termination, if a pipe hasn't reconnected, it would just attempt to be erased from the pipes list again, which is reasonable

The check_write method does not use the passed message.
The parameter was needed to implement the swap.
As the swap is not supported anymore, it is safe to remove this parameter.

- anonymous contributor

This reverts commit 7b7d4042.

However, the "durable socket" behaviour wasn't re-added.
Identities are used solely for routing in REQ/REP pattern.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Up to now the complexity of fair-queueing in XREP was O(n).
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

So far there was no distinction between message parts used by 0MQ
and message parts used by user. Now, the message parts used by 0MQ
are marked as 'LABEL'.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

pipe_t now correctly drops pointer to the underlying pipe when
sending pipe_term_ack command.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>