semaphore.h File Reference

Counting semaphore confined to a single process. More...

#include <memory>
#include "./macros.h"

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Classes
class	vlink::Semaphore
	In-process counting semaphore with an optional acquire timeout. More...

Namespaces
	vlink

Detailed Description

Counting semaphore confined to a single process.

vlink::Semaphore offers classic Dijkstra P/V semantics for in-process synchronisation, built on top of std::mutex and the project ConditionVariable (which uses CLOCK_MONOTONIC on Linux so NTP-induced jumps do not skew wait timeouts). It is the right primitive for permit-style throttling, bounded-queue back-pressure, and producer/consumer handoff.

Wait/post interaction between two threads:

*   Producer                        Consumer
*      |                               |
*      | release(n) -- counter+=n ---> |
*      |                               | acquire(m): blocks while counter<m
*      |                               | counter -= m; resumes
* 

Note

• release() acquires the internal mutex, so it must not be called from a signal handler. Use SysSemaphore or sem_post directly for signal-context posts.
• reset(true) wakes every blocked waiter and returns false to them; use only during controlled shutdown.

Example

vlink::Semaphore sem(0);
 
std::thread producer([&] {
  do_work();
  sem.release();
});
 
if (sem.acquire(1, 100)) {
  consume_result();
} else {
  handle_timeout();
}
 
producer.join();