Don't copy contiguous bytes on reception

[fuzzypixelz]

This uses the slices iterator API of zenoh-c to avoid unecessarily copying bytes into an owned slice, if and only if the bytes is made up of exactly one slice.

[fuzzypixelz]

The aim of this pull request is to fix high latency for relatively large topics (e.g. 1 MB tagus) in the single-process iRobot benchmark with --ipc off. Results were obtained using the Mont Blanc topology on an Ubuntu 24.04.1 LTS machine with an Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz.

dd82e84

node	topic	size_b	mean_us	min_us	max_us
ponce	tagus	1000000	3016	2512	5705
geneva	tagus	1000000	3513	2997	6457
mandalay	tagus	1000000	2678	2214	5233

eed223a

node	topic	size_b	mean_us	min_us	max_us
ponce	tagus	1000000	1651	1363	2252
geneva	tagus	1000000	1875	1557	2563
mandalay	tagus	1000000	1390	1151	1867

eed223a + 401016c

node	topic	size_b	mean_us	min_us	max_us
ponce	tagus	1000000	393	257	1301
geneva	tagus	1000000	657	438	1701
mandalay	tagus	1000000	108	68	650

[clalancette]

Thanks for opening the PR.

We are just in the process of converting to zenoh-cpp as our API in #327. I'm assuming a similar idea will work there, but until we merge that, I'm going to mark this as a draft PR, and we can revisit it once we've merged that in.

[fuzzypixelz]

Thanks for opening the PR.

We are just in the process of converting to zenoh-cpp as our API in #327. I'm assuming a similar idea will work there, but until we merge that, I'm going to mark this as a draft PR, and we can revisit it once we've merged that in.

The bytes slice iterator API exists in zenoh-cpp, however there is no z_bytes_to_slice equivalent so we would need to manually allocate a buffer in that case or just use as_vector. We could coordinate potential changes to the zenoh-cpp API if necessary.

[clalancette]

All right, we've now merged in #327. Please rebase this and make any necessary changes to adapt to zenoh-cpp, and then we can do a full review of it.