source: vendor/current/lib/tevent/tevent_queue.c

/*
   Unix SMB/CIFS implementation.
   Infrastructure for async requests
   Copyright (C) Volker Lendecke 2008
   Copyright (C) Stefan Metzmacher 2009

     ** NOTE! The following LGPL license applies to the tevent
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "tevent.h"
#include "tevent_internal.h"
#include "tevent_util.h"

struct tevent_queue_entry {
        struct tevent_queue_entry *prev, *next;
        struct tevent_queue *queue;

        bool triggered;

        struct tevent_req *req;
        struct tevent_context *ev;

        tevent_queue_trigger_fn_t trigger;
        void *private_data;
};

struct tevent_queue {
        const char *name;
        const char *location;

        bool running;
        struct tevent_immediate *immediate;

        size_t length;
        struct tevent_queue_entry *list;
};

static void tevent_queue_immediate_trigger(struct tevent_context *ev,
                                           struct tevent_immediate *im,
                                           void *private_data);

static int tevent_queue_entry_destructor(struct tevent_queue_entry *e)
{
        struct tevent_queue *q = e->queue;

        if (!q) {
                return 0;
        }

        DLIST_REMOVE(q->list, e);
        q->length--;

        if (!q->running) {
                return 0;
        }

        if (!q->list) {
                return 0;
        }

        if (q->list->triggered) {
                return 0;
        }

        tevent_schedule_immediate(q->immediate,
                                  q->list->ev,
                                  tevent_queue_immediate_trigger,
                                  q);

        return 0;
}

static int tevent_queue_destructor(struct tevent_queue *q)
{
        q->running = false;

        while (q->list) {
                struct tevent_queue_entry *e = q->list;
                talloc_free(e);
        }

        return 0;
}

struct tevent_queue *_tevent_queue_create(TALLOC_CTX *mem_ctx,
                                          const char *name,
                                          const char *location)
{
        struct tevent_queue *queue;

        queue = talloc_zero(mem_ctx, struct tevent_queue);
        if (!queue) {
                return NULL;
        }

        queue->name = talloc_strdup(queue, name);
        if (!queue->name) {
                talloc_free(queue);
                return NULL;
        }
        queue->immediate = tevent_create_immediate(queue);
        if (!queue->immediate) {
                talloc_free(queue);
                return NULL;
        }

        queue->location = location;

        /* queue is running by default */
        queue->running = true;

        talloc_set_destructor(queue, tevent_queue_destructor);
        return queue;
}

static void tevent_queue_immediate_trigger(struct tevent_context *ev,
                                           struct tevent_immediate *im,
                                           void *private_data)
{
        struct tevent_queue *q =
                talloc_get_type_abort(private_data,
                struct tevent_queue);

        if (!q->running) {
                return;
        }

        if (!q->list) {
                return;
        }

        q->list->triggered = true;
        q->list->trigger(q->list->req, q->list->private_data);
}

static struct tevent_queue_entry *tevent_queue_add_internal(
                                        struct tevent_queue *queue,
                                        struct tevent_context *ev,
                                        struct tevent_req *req,
                                        tevent_queue_trigger_fn_t trigger,
                                        void *private_data,
                                        bool allow_direct)
{
        struct tevent_queue_entry *e;

        e = talloc_zero(req, struct tevent_queue_entry);
        if (e == NULL) {
                return NULL;
        }

        e->queue = queue;
        e->req = req;
        e->ev = ev;
        e->trigger = trigger;
        e->private_data = private_data;

        /*
         * if there is no trigger, it is just a blocker
         */
        if (trigger == NULL) {
                e->triggered = true;
        }

        if (queue->length > 0) {
                /*
                 * if there are already entries in the
                 * queue do not optimize.
                 */
                allow_direct = false;
        }

        if (req->async.fn != NULL) {
                /*
                 * If the callers wants to optimize for the
                 * empty queue case, call the trigger only
                 * if there is no callback defined for the
                 * request yet.
                 */
                allow_direct = false;
        }

        DLIST_ADD_END(queue->list, e);
        queue->length++;
        talloc_set_destructor(e, tevent_queue_entry_destructor);

        if (!queue->running) {
                return e;
        }

        if (queue->list->triggered) {
                return e;
        }

        /*
         * If allowed we directly call the trigger
         * avoiding possible delays caused by
         * an immediate event.
         */
        if (allow_direct) {
                queue->list->triggered = true;
                queue->list->trigger(queue->list->req,
                                     queue->list->private_data);
                return e;
        }

        tevent_schedule_immediate(queue->immediate,
                                  queue->list->ev,
                                  tevent_queue_immediate_trigger,
                                  queue);

        return e;
}

bool tevent_queue_add(struct tevent_queue *queue,
                      struct tevent_context *ev,
                      struct tevent_req *req,
                      tevent_queue_trigger_fn_t trigger,
                      void *private_data)
{
        struct tevent_queue_entry *e;

        e = tevent_queue_add_internal(queue, ev, req,
                                      trigger, private_data, false);
        if (e == NULL) {
                return false;
        }

        return true;
}

struct tevent_queue_entry *tevent_queue_add_entry(
                                        struct tevent_queue *queue,
                                        struct tevent_context *ev,
                                        struct tevent_req *req,
                                        tevent_queue_trigger_fn_t trigger,
                                        void *private_data)
{
        return tevent_queue_add_internal(queue, ev, req,
                                         trigger, private_data, false);
}

struct tevent_queue_entry *tevent_queue_add_optimize_empty(
                                        struct tevent_queue *queue,
                                        struct tevent_context *ev,
                                        struct tevent_req *req,
                                        tevent_queue_trigger_fn_t trigger,
                                        void *private_data)
{
        return tevent_queue_add_internal(queue, ev, req,
                                         trigger, private_data, true);
}

void tevent_queue_start(struct tevent_queue *queue)
{
        if (queue->running) {
                /* already started */
                return;
        }

        queue->running = true;

        if (!queue->list) {
                return;
        }

        if (queue->list->triggered) {
                return;
        }

        tevent_schedule_immediate(queue->immediate,
                                  queue->list->ev,
                                  tevent_queue_immediate_trigger,
                                  queue);
}

void tevent_queue_stop(struct tevent_queue *queue)
{
        queue->running = false;
}

size_t tevent_queue_length(struct tevent_queue *queue)
{
        return queue->length;
}

bool tevent_queue_running(struct tevent_queue *queue)
{
        return queue->running;
}

struct tevent_queue_wait_state {
        uint8_t dummy;
};

static void tevent_queue_wait_trigger(struct tevent_req *req,
                                      void *private_data);

struct tevent_req *tevent_queue_wait_send(TALLOC_CTX *mem_ctx,
                                          struct tevent_context *ev,
                                          struct tevent_queue *queue)
{
        struct tevent_req *req;
        struct tevent_queue_wait_state *state;
        bool ok;

        req = tevent_req_create(mem_ctx, &state,
                                struct tevent_queue_wait_state);
        if (req == NULL) {
                return NULL;
        }

        ok = tevent_queue_add(queue, ev, req,
                              tevent_queue_wait_trigger,
                              NULL);
        if (!ok) {
                tevent_req_oom(req);
                return tevent_req_post(req, ev);
        }

        return req;
}

static void tevent_queue_wait_trigger(struct tevent_req *req,
                                         void *private_data)
{
        tevent_req_done(req);
}

bool tevent_queue_wait_recv(struct tevent_req *req)
{
        enum tevent_req_state state;
        uint64_t err;

        if (tevent_req_is_error(req, &state, &err)) {
                tevent_req_received(req);
                return false;
        }

        tevent_req_received(req);
        return true;
}