GitLab

A lighweight, lockless multi-reader/multi-writer FIFO with a
base-offset variant which can work over a memory segment shared
between processes. Scalar data or simple (small!) aggregates are
conveyed though a tube inside canisters which exactly fit their type.
By design, a tube is meant to be a basic, spartan mechanism: it
imposes no usage policy whatsoever on users.

As a result, a tube is strictly non-blocking, it solely detects and
notifies the caller on return about empty input (no message in) and
output contention (no buffer space for output). If required, the
caller can implement blocking states, typically with a pair of EVL
semaphores, e.g. setting up a tube conveying integers which supports
blocking mode:

    DECLARE_EVL_TUBE_CANISTER(canister_type, int); /* defines struct canister_type */
    DECLARE_EVL_TUBE(tube_type, cannister_type) tube;
    struct cannister_type items[1024];

    evl_init_tube(&tube, items, 1024);
    evl_new_sem(&in, ...);
    evl_new_sem_any(&out, CLOCK_MONOTONIC, tube.max_items, ...);

    evl_get_sem(&in, ...);           @      evl_get_sem(&out);
    evl_tube_receive(&tube, ...);    @      evl_tube_send(&tube, ...);
    evl_put_sem(&out);               @      evl_put_sem(&in, ...);