Module time 

Monotonic time for portable node code (issue #504).

phase-359 W10 — rmw-cffi, not any(std, rmw-cffi): the clock is the platform port’s, and a build with no port has none to offer. Monotonic time for portable node code (issue #504).

Node packages are platform-agnostic: the same crate compiles into a POSIX, FreeRTOS, or Zephyr image, so it can reach neither the per-platform timing types nor the nros_platform_clock_ns C export directly. This module is the portable spelling. Uses that motivated it: dt in control laws (assuming the nominal period silently misintegrates whenever a callback runs late), timestamping published state, and coarse in-node watchdogs.

Semantics: monotonic since an unspecified epoch (process start or boot). This is explicitly NOT ROS time — no sim-time, no epoch meaning, no cross-machine comparability. Compare instants, never interpret one absolutely.

Clock source mirrors the executor’s timer accounting (nros-node/src/executor/spin.rs), and phase-359 W10 follow-up had to RESTORE that — the sentence had gone false:

• rmw-cffi builds (a platform port is linked): the platform’s nros_platform_clock_ns export, on either flavour. Same linkage contract the executor and the wake primitives already rely on, so this adds no new requirement. Resolution is whatever the platform delivers (issue #502: sub-tick on FreeRTOS Cortex-M, tick-quantized on ThreadX).
• std without a port: std::time::Instant, anchored at first use. The claim that stood here — “real and shipped, the metadata probe compiles node code with std and no port” — was WRONG. The probe links nros-platform-cffi with posix-c-port and resolves rmw-cffi, so it takes the arm above. This arm has no in-tree consumer: nothing calls now() anywhere in the tree.
• Neither: no clock source; this module is absent.

The order used to be the other way round, std first, which meant every NATIVE build (std AND a port) read Instant here while the executor read the port — two monotonic sources with different epochs in one image, under a doc claiming they were one. W10 moved the executor onto the port whenever a port exists; this module was not moved with it. Two clocks are only harmless while nobody compares them, and the whole purpose of this module is dt across callbacks the executor scheduled.

Functions

now

Monotonic time since an unspecified epoch.

now_us

Convenience: now as whole microseconds.