Allow messages with long vectors

[mschubert]

rzmq currently does not allow sending long vectors as messages. Those are array-like objects whose size is bigger than the integer maximum.

.Machine$integer.max
# [1] 2147483647

Initializing a message object (or using rzmq::send.socket) works with vectors smaller than the integer size maximum,

z = rnorm(2.6e8)
object.size(z)
# 2080000048 bytes
x = rzmq::init.message(z) # works

but fails for vectors that are bigger:

z = rnorm(2.7e8)
object.size(z)
# 2160000048 bytes
x = rzmq::init.message(z)
# Error in rzmq::init.message(z) :
#   long vectors not supported yet: ../../src/include/Rinlinedfuns.h:519

The reason for this is that the serialized object's length is queried using the length function, which returns an integer and triggers an R internal assertion error.

If we instead use Rf_xlength (size_t type), the length query succeeds and we can serialize larger vectors to rzmq messages.

While this could be seen as a guard to not serialize large objects, I would argue that the limit on what makes sense is application specific and packages using rzmq should set their own limits.

[jeroen]

Are there any other places where we should replace int with x_len_t ?

[codecov-io]

Codecov Report

Merging #47 into master will not change coverage. The diff coverage is 50%.

@@           Coverage Diff           @@
##           master      #47   +/-   ##
=======================================
  Coverage   33.72%   33.72%           
=======================================
  Files           4        4           
  Lines         685      685           
=======================================
  Hits          231      231           
  Misses        454      454

Impacted Files	Coverage Δ
src/interface.cpp	28.71% <50%> (ø)	:arrow_up:

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[mschubert]

Message sizes are never explicitly stored in interface.cpp, this is all handled by ZeroMQ.

So no, no need to replace anything else as far as I can tell.