sync.h

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/*
 *
 * Copyright 2015 gRPC authors.
 *
 * 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.
 *
 */

#ifndef GRPC_SUPPORT_SYNC_H
#define GRPC_SUPPORT_SYNC_H

#include <grpc/impl/codegen/gpr_types.h> /* for gpr_timespec */
#include <grpc/impl/codegen/sync.h>

#ifdef __cplusplus
extern "C" {
#endif

GPRAPI void gpr_mu_init(gpr_mu* mu);

GPRAPI void gpr_mu_destroy(gpr_mu* mu);

GPRAPI void gpr_mu_lock(gpr_mu* mu);

GPRAPI void gpr_mu_unlock(gpr_mu* mu);

GPRAPI int gpr_mu_trylock(gpr_mu* mu);

GPRAPI void gpr_cv_init(gpr_cv* cv);

GPRAPI void gpr_cv_destroy(gpr_cv* cv);

GPRAPI int gpr_cv_wait(gpr_cv* cv, gpr_mu* mu, gpr_timespec abs_deadline);

GPRAPI void gpr_cv_signal(gpr_cv* cv);

GPRAPI void gpr_cv_broadcast(gpr_cv* cv);

GPRAPI void gpr_once_init(gpr_once* once, void (*init_routine)(void));

GPRAPI void gpr_event_init(gpr_event* ev);

GPRAPI void gpr_event_set(gpr_event* ev, void* value);

GPRAPI void* gpr_event_get(gpr_event* ev);

GPRAPI void* gpr_event_wait(gpr_event* ev, gpr_timespec abs_deadline);

GPRAPI void gpr_ref_init(gpr_refcount* r, int n);

GPRAPI void gpr_ref(gpr_refcount* r);

GPRAPI void gpr_ref_non_zero(gpr_refcount* r);

GPRAPI void gpr_refn(gpr_refcount* r, int n);

GPRAPI int gpr_unref(gpr_refcount* r);

GPRAPI int gpr_ref_is_unique(gpr_refcount* r);

GPRAPI void gpr_stats_init(gpr_stats_counter* c, intptr_t n);

GPRAPI void gpr_stats_inc(gpr_stats_counter* c, intptr_t inc);

GPRAPI intptr_t gpr_stats_read(const gpr_stats_counter* c);

#if 0

#define N 4

   typedef struct queue {
     gpr_cv non_empty;  /* Signalled when length becomes non-zero. */
     gpr_cv non_full;   /* Signalled when length becomes non-N. */
     gpr_mu mu;         /* Protects all fields below.
                            (That is, except during initialization or
                            destruction, the fields below should be accessed
                            only by a thread that holds mu.) */
     int head;           /* Index of head of queue 0..N-1. */
     int length;         /* Number of valid elements in queue 0..N. */
     int elem[N];        /* elem[head .. head+length-1] are queue elements. */
   } queue;

   /* Initialize *q. */
   void queue_init(queue *q) {
     gpr_mu_init(&q->mu);
     gpr_cv_init(&q->non_empty);
     gpr_cv_init(&q->non_full);
     q->head = 0;
     q->length = 0;
   }

   /* Free storage associated with *q. */
   void queue_destroy(queue *q) {
     gpr_mu_destroy(&q->mu);
     gpr_cv_destroy(&q->non_empty);
     gpr_cv_destroy(&q->non_full);
   }

   /* Wait until there is room in *q, then append x to *q. */
   void queue_append(queue *q, int x) {
     gpr_mu_lock(&q->mu);
     /* To wait for a predicate without a deadline, loop on the negation of the
        predicate, and use gpr_cv_wait(..., gpr_inf_future) inside the loop
        to release the lock, wait, and reacquire on each iteration.  Code that
        makes the condition true should use gpr_cv_broadcast() on the
        corresponding condition variable.  The predicate must be on state
        protected by the lock.  */
     while (q->length == N) {
       gpr_cv_wait(&q->non_full, &q->mu, gpr_inf_future);
     }
     if (q->length == 0) {  /* Wake threads blocked in queue_remove(). */
       /* It's normal to use gpr_cv_broadcast() or gpr_signal() while
          holding the lock. */
       gpr_cv_broadcast(&q->non_empty);
     }
     q->elem[(q->head + q->length) % N] = x;
     q->length++;
     gpr_mu_unlock(&q->mu);
   }

   /* If it can be done without blocking, append x to *q and return non-zero.
      Otherwise return 0. */
   int queue_try_append(queue *q, int x) {
     int result = 0;
     if (gpr_mu_trylock(&q->mu)) {
       if (q->length != N) {
         if (q->length == 0) {  /* Wake threads blocked in queue_remove(). */
           gpr_cv_broadcast(&q->non_empty);
         }
         q->elem[(q->head + q->length) % N] = x;
         q->length++;
         result = 1;
       }
       gpr_mu_unlock(&q->mu);
     }
     return result;
   }

   /* Wait until the *q is non-empty or deadline abs_deadline passes.  If the
      queue is non-empty, remove its head entry, place it in *head, and return
      non-zero.  Otherwise return 0.  */
   int queue_remove(queue *q, int *head, gpr_timespec abs_deadline) {
     int result = 0;
     gpr_mu_lock(&q->mu);
     /* To wait for a predicate with a deadline, loop on the negation of the
        predicate or until gpr_cv_wait() returns true.  Code that makes
        the condition true should use gpr_cv_broadcast() on the corresponding
        condition variable.  The predicate must be on state protected by the
        lock. */
     while (q->length == 0 &&
            !gpr_cv_wait(&q->non_empty, &q->mu, abs_deadline)) {
     }
     if (q->length != 0) {    /* Queue is non-empty. */
       result = 1;
       if (q->length == N) {  /* Wake threads blocked in queue_append(). */
         gpr_cv_broadcast(&q->non_full);
       }
       *head = q->elem[q->head];
       q->head = (q->head + 1) % N;
       q->length--;
     } /* else deadline exceeded */
     gpr_mu_unlock(&q->mu);
     return result;
   }
#endif /* 0 */

#ifdef __cplusplus
}  // extern "C"

namespace grpc_core {

class mu_guard {
 public:
  mu_guard(gpr_mu* mu) : mu_(mu) { gpr_mu_lock(mu); }
  ~mu_guard() { gpr_mu_unlock(mu_); }

  mu_guard(const mu_guard&) = delete;
  mu_guard& operator=(const mu_guard&) = delete;

 private:
  gpr_mu* const mu_;
};

}  // namespace grpc_core
#endif

#endif /* GRPC_SUPPORT_SYNC_H */