CnxSharedMutex struct

#include <include/Cnx/sync/SharedMutex.h>

CnxSharedMutex is the generic (it's not timed or recursive) reader-writer mutex provided by Cnx. It's directly comparable to C++'s std::shared_mutex and is suitable for any situation where a reader-writer mutex is necessary.

Example:

// MyThing.h
#include <Cnx/sync/SharedMutex.h>
static MyType my_very_important_thing;
static CnxSharedMutex* my_thing_mutex;

void init_my_thing(void);
void update_my_thing(u64 value);
u64 get_value_from_my_thing(void);

// MyThing.c
#include <Cnx/Allocators.h>
#include "MyThing.h"
void init_my_thing(void) {
    if(my_thing_mutex == nullptr) {
        my_thing_mutex = cnx_allocator_allocate_t(CnxSharedMutex, DEFAULT_ALLOCATOR);
        *my_thing_mutex = cnx_shared_mutex_new();

        cnx_shared_mutex_lock(my_thing_mutex);
        my_very_important_thing = {
        // important intialization
        };
        cnx_shared_mutex_unlock(my_thing_mutex);
    }
}

// only one thread at a time can `update_my_thing`, because it uses exclusive locking
void update_my_thing(u64 value) {
    cnx_shared_mutex_lock(my_thing_mutex);
    my_very_important_thing.value = value;
    cnx_shared_mutex_unlock(my_thing_mutex);
}

// any number of threads can `get_value_from_my_thing` without blocking eachother,
// because it uses shared locking.
u64 get_value_from_my_thing(void) {
    cnx_shared_mutex_lock_shared(my_thing_mutex);
    let val = my_very_important_thing.value;
    cnx_shared_mutex_unlock_shared(my_thing_mutex);
    return val;
}


// do some compute intensive task...
// update the value
update_my_thing(new_value);

my_val = get_value_from_my_thing();
// do something with my_val

let_mut newval = get_value_from_my_thing();
while(newval == my_val) {
    cnx_this_thread_sleep_for(cnx_milliseconds(100));
    newval = get_value_from_my_thing();
}

my_val = newval;
// do something with new value