OSMemoryNotification.c [plain text]
#include <errno.h>
#include <libkern/OSMemoryNotification.h>
#include <mach/mach.h>
#include <notify.h>
#include <stdlib.h>
#include <sys/time.h>
#include <dispatch/dispatch.h>
#include <dispatch/private.h>
const char *kOSMemoryNotificationName = "com.apple.system.memorystatus";
struct _OSMemoryNotification {
int token;
mach_port_t port;
};
int
OSMemoryNotificationCreate(OSMemoryNotificationRef *note)
{
OSMemoryNotificationRef ref = malloc(sizeof(struct _OSMemoryNotification));
if (NULL == ref) {
return ENOMEM;
}
if (NOTIFY_STATUS_OK != notify_register_mach_port(kOSMemoryNotificationName, &ref->port, 0, &ref->token))
return ENOMEM;
*note = ref;
return 0;
}
int
OSMemoryNotificationDestroy(OSMemoryNotificationRef note)
{
if (NOTIFY_STATUS_OK != notify_cancel(note->token))
return EINVAL;
if (KERN_SUCCESS != mach_port_deallocate(mach_task_self(), note->port))
return EINVAL;
free(note);
return 0;
}
int
OSMemoryNotificationWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level)
{
return OSMemoryNotificationTimedWait(note, level, NULL);
}
static mach_msg_timeout_t
abs_to_timeout(const struct timeval *abstime)
{
struct timeval rel, now;
gettimeofday(&now, NULL);
rel.tv_usec = abstime->tv_usec - now.tv_usec;
rel.tv_sec = abstime->tv_sec - now.tv_sec;
if (rel.tv_usec < 0) {
rel.tv_usec += 1000000;
rel.tv_sec--;
}
if (((int)rel.tv_sec < 0) || ((rel.tv_sec == 0) && (rel.tv_usec == 0))) {
return 0;
}
return rel.tv_sec * 1000 + rel.tv_usec / 1000;
}
int
OSMemoryNotificationTimedWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level, const struct timeval *abstime)
{
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
dispatch_retain(sema);
dispatch_source_t memoryNotificationSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_VM, 0, DISPATCH_VM_PRESSURE, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0));
dispatch_source_set_event_handler(memoryNotificationSource, ^{
dispatch_semaphore_signal(sema);
dispatch_release(sema);
});
dispatch_resume(memoryNotificationSource);
dispatch_time_t waitTime = DISPATCH_TIME_FOREVER;
if (abstime) {
mach_msg_timeout_t timeout = abs_to_timeout(abstime);
waitTime = dispatch_time(DISPATCH_TIME_NOW, timeout * 1e6);
}
long ret = dispatch_semaphore_wait(sema, waitTime);
dispatch_release(sema);
dispatch_release(memoryNotificationSource);
if (ret != 0) {
return ETIMEDOUT;
}
if (level) {
*level = OSMemoryNotificationLevelUrgent;
}
return 0;
}
OSMemoryNotificationLevel OSMemoryNotificationCurrentLevel(void)
{
return OSMemoryNotificationLevelNormal;
}