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Semaphore

Semaphore class hierarchy

A semaphore manages thread access to a pool of shared resources of a certain type.

Semaphore class reference

Public Member Functions
 Semaphore (int32_t count=0)
 Create and Initialize a Semaphore object used for managing resources. More...
 Semaphore (int32_t count, uint16_t max_count)
 Create and Initialize a Semaphore object used for managing resources. More...
int32_t wait (uint32_t millisec=osWaitForever)
 Wait until a Semaphore resource becomes available. More...
int32_t wait_until (uint64_t millisec)
 Wait until a Semaphore resource becomes available. More...
osStatus release (void)
 Release a Semaphore resource that was obtain with Semaphore::wait. More...
 ~Semaphore ()
 Semaphore destructor. More...

Semaphore example

Use Semaphore to protect printf().

#include "mbed.h"

Semaphore one_slot(1);
Thread t2;
Thread t3;

void test_thread(void const *name) {
    while (true) {
        one_slot.wait();
        printf("%s\n\r", (const char*)name);
        wait(1);
        one_slot.release();
    }
}

int main (void) {
    t2.start(callback(test_thread, (void *)"Th 2"));
    t3.start(callback(test_thread, (void *)"Th 3"));

    test_thread((void *)"Th 1");
}

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