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/*
* Copyright (c) 2017 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <LongBow/runtime.h>
#include <parc/concurrent/parc_Notifier.h>
#include <parc/algol/parc_Object.h>
#ifdef __GNUC__
#define ATOMIC_ADD_AND_FETCH(ptr, increment) __sync_add_and_fetch(ptr, increment)
#define ATOMIC_BOOL_CAS(ptr, oldvalue, newvalue) __sync_bool_compare_and_swap(ptr, oldvalue, newvalue)
#define ATOMIC_FETCH(ptr) ATOMIC_ADD_AND_FETCH(ptr, 0)
#define ATOMIC_SET(ptr, oldvalue, newvalue) ATOMIC_BOOL_CAS(ptr, oldvalue, newvalue)
#else
#error "Only GNUC supported, we need atomic operations"
#endif
struct parc_notifier {
volatile int paused;
// If the notifications are paused and there is an event,
// we indicate that we skipped a notify
volatile int skippedNotify;
#define PARCNotifierWriteFd 1
#define PARCNotifierReadFd 0
int fds[2];
};
static void
_parcNotifier_Finalize(PARCNotifier **notifierPtr)
{
PARCNotifier *notifier = *notifierPtr;
close(notifier->fds[0]);
close(notifier->fds[1]);
}
parcObject_ExtendPARCObject(PARCNotifier, _parcNotifier_Finalize, NULL, NULL, NULL, NULL, NULL, NULL);
static bool
_parcNotifier_MakeNonblocking(PARCNotifier *notifier)
{
// set the read side to be non-blocking
int flags = fcntl(notifier->fds[PARCNotifierReadFd], F_GETFL, 0);
if (flags == 0) {
if (fcntl(notifier->fds[PARCNotifierReadFd], F_SETFL, flags | O_NONBLOCK) == 0) {
return true;
}
}
perror("fcntl error");
return false;
}
PARCNotifier *
parcNotifier_Create(void)
{
PARCNotifier *notifier = parcObject_CreateInstance(PARCNotifier);
if (notifier) {
notifier->paused = false;
notifier->skippedNotify = false;
int failure = pipe(notifier->fds);
assertFalse(failure, "Error on pipe: %s", strerror(errno));
if (!_parcNotifier_MakeNonblocking(notifier)) {
parcObject_Release((void **) ¬ifier);
}
}
return notifier;
}
parcObject_ImplementAcquire(parcNotifier, PARCNotifier);
parcObject_ImplementRelease(parcNotifier, PARCNotifier);
int
parcNotifier_Socket(PARCNotifier *notifier)
{
return notifier->fds[PARCNotifierReadFd];
}
bool
parcNotifier_Notify(PARCNotifier *notifier)
{
if (ATOMIC_BOOL_CAS(¬ifier->paused, 0, 1)) {
// old value was "0" so we need to send a notification
uint8_t one = 1;
ssize_t written;
do {
written = write(notifier->fds[PARCNotifierWriteFd], &one, 1);
assertTrue(written >= 0, "Error writing to socket %d: %s", notifier->fds[PARCNotifierWriteFd], strerror(errno));
} while (written == 0);
return true;
} else {
// we're paused, so count up the pauses
ATOMIC_ADD_AND_FETCH(¬ifier->skippedNotify, 1);
return false;
}
}
void
parcNotifier_PauseEvents(PARCNotifier *notifier)
{
// reset the skipped counter so we count from now until the StartEvents call
notifier->skippedNotify = 0;
ATOMIC_BOOL_CAS(¬ifier->paused, 0, 1);
// now clear out the socket
uint8_t buffer[16];
while (read(notifier->fds[PARCNotifierReadFd], &buffer, 16) > 0) {
;
}
}
void
parcNotifier_StartEvents(PARCNotifier *notifier)
{
ATOMIC_BOOL_CAS(¬ifier->paused, 1, 0);
if (notifier->skippedNotify) {
// we missed some notifications, so re-signal ourself
parcNotifier_Notify(notifier);
}
}
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