Initial checkin of gRPC to third_party/

third_party/grpc/include/grpc/impl/codegen/sync.h

Index: third_party/grpc/include/grpc/impl/codegen/sync.h
diff --git a/third_party/grpc/include/grpc/impl/codegen/sync.h b/third_party/grpc/include/grpc/impl/codegen/sync.h
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+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_IMPL_CODEGEN_SYNC_H
+#define GRPC_IMPL_CODEGEN_SYNC_H
+/* Synchronization primitives for GPR.
+
+   The type  gpr_mu              provides a non-reentrant mutex (lock).
+
+   The type  gpr_cv              provides a condition variable.
+
+   The type  gpr_once            provides for one-time initialization.
+
+   The type gpr_event            provides one-time-setting, reading, and
+                                 waiting of a void*, with memory barriers.
+
+   The type gpr_refcount         provides an object reference counter,
+                                 with memory barriers suitable to control
+                                 object lifetimes.
+
+   The type gpr_stats_counter    provides an atomic statistics counter. It
+                                 provides no memory barriers.
+ */
+
+/* Platform-specific type declarations of gpr_mu and gpr_cv.   */
+#include <grpc/impl/codegen/port_platform.h>
+#include <grpc/impl/codegen/sync_generic.h>
+
+#if defined(GPR_POSIX_SYNC)
+#include <grpc/impl/codegen/sync_posix.h>
+#elif defined(GPR_WIN32)
+#include <grpc/impl/codegen/sync_win32.h>
+#elif !defined(GPR_CUSTOM_SYNC)
+#error Unable to determine platform for sync
+#endif
+
+#include <grpc/impl/codegen/time.h> /* for gpr_timespec */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* --- Mutex interface ---
+
+   At most one thread may hold an exclusive lock on a mutex at any given time.
+   Actions taken by a thread that holds a mutex exclusively happen after
+   actions taken by all previous holders of the mutex.  Variables of type
+   gpr_mu are uninitialized when first declared.  */
+
+/* Initialize *mu.  Requires:  *mu uninitialized.  */
+GPRAPI void gpr_mu_init(gpr_mu *mu);
+
+/* Cause *mu no longer to be initialized, freeing any memory in use.  Requires:
+   *mu initialized; no other concurrent operation on *mu.  */
+GPRAPI void gpr_mu_destroy(gpr_mu *mu);
+
+/* Wait until no thread has a lock on *mu, cause the calling thread to own an
+   exclusive lock on *mu, then return.  May block indefinitely or crash if the
+   calling thread has a lock on *mu.  Requires:  *mu initialized.  */
+GPRAPI void gpr_mu_lock(gpr_mu *mu);
+
+/* Release an exclusive lock on *mu held by the calling thread.  Requires:  *mu
+   initialized; the calling thread holds an exclusive lock on *mu.  */
+GPRAPI void gpr_mu_unlock(gpr_mu *mu);
+
+/* Without blocking, attempt to acquire an exclusive lock on *mu for the
+   calling thread, then return non-zero iff success.  Fail, if any thread holds
+   the lock; succeeds with high probability if no thread holds the lock.
+   Requires:  *mu initialized.  */
+GPRAPI int gpr_mu_trylock(gpr_mu *mu);
+
+/* --- Condition variable interface ---
+
+   A while-loop should be used with gpr_cv_wait() when waiting for conditions
+   to become true.  See the example below.  Variables of type gpr_cv are
+   uninitialized when first declared.  */
+
+/* Initialize *cv.  Requires:  *cv uninitialized.  */
+GPRAPI void gpr_cv_init(gpr_cv *cv);
+
+/* Cause *cv no longer to be initialized, freeing any memory in use.  Requires:
+   *cv initialized; no other concurrent operation on *cv.*/
+GPRAPI void gpr_cv_destroy(gpr_cv *cv);
+
+/* Atomically release *mu and wait on *cv.  When the calling thread is woken
+   from *cv or the deadline abs_deadline is exceeded, execute gpr_mu_lock(mu)
+   and return whether the deadline was exceeded.  Use
+   abs_deadline==gpr_inf_future for no deadline.  abs_deadline can be either
+   an absolute deadline, or a GPR_TIMESPAN.  May return even when not
+   woken explicitly.  Requires:  *mu and *cv initialized; the calling thread
+   holds an exclusive lock on *mu.  */
+GPRAPI int gpr_cv_wait(gpr_cv *cv, gpr_mu *mu, gpr_timespec abs_deadline);
+
+/* If any threads are waiting on *cv, wake at least one.
+   Clients may treat this as an optimization of gpr_cv_broadcast()
+   for use in the case where waking more than one waiter is not useful.
+   Requires:  *cv initialized.  */
+GPRAPI void gpr_cv_signal(gpr_cv *cv);
+
+/* Wake all threads waiting on *cv.  Requires:  *cv initialized.  */
+GPRAPI void gpr_cv_broadcast(gpr_cv *cv);
+
+/* --- One-time initialization ---
+
+   gpr_once must be declared with static storage class, and initialized with
+   GPR_ONCE_INIT.  e.g.,
+     static gpr_once once_var = GPR_ONCE_INIT;     */
+
+/* Ensure that (*init_routine)() has been called exactly once (for the
+   specified gpr_once instance) and then return.
+   If multiple threads call gpr_once() on the same gpr_once instance, one of
+   them will call (*init_routine)(), and the others will block until that call
+   finishes.*/
+GPRAPI void gpr_once_init(gpr_once *once, void (*init_routine)(void));
+
+/* --- One-time event notification ---
+
+  These operations act on a gpr_event, which should be initialized with
+  gpr_ev_init(), or with GPR_EVENT_INIT if static, e.g.,
+       static gpr_event event_var = GPR_EVENT_INIT;
+  It requires no destruction.  */
+
+/* Initialize *ev. */
+GPRAPI void gpr_event_init(gpr_event *ev);
+
+/* Set *ev so that gpr_event_get() and gpr_event_wait() will return value.
+   Requires:  *ev initialized; value != NULL; no prior or concurrent calls to
+   gpr_event_set(ev, ...) since initialization.  */
+GPRAPI void gpr_event_set(gpr_event *ev, void *value);
+
+/* Return the value set by gpr_event_set(ev, ...), or NULL if no such call has
+   completed.  If the result is non-NULL, all operations that occurred prior to
+   the gpr_event_set(ev, ...) set will be visible after this call returns.
+   Requires:  *ev initialized.  This operation is faster than acquiring a mutex
+   on most platforms.  */
+GPRAPI void *gpr_event_get(gpr_event *ev);
+
+/* Wait until *ev is set by gpr_event_set(ev, ...), or abs_deadline is
+   exceeded, then return gpr_event_get(ev).  Requires:  *ev initialized.  Use
+   abs_deadline==gpr_inf_future for no deadline.  When the event has been
+   signalled before the call, this operation is faster than acquiring a mutex
+   on most platforms.  */
+GPRAPI void *gpr_event_wait(gpr_event *ev, gpr_timespec abs_deadline);
+
+/* --- Reference counting ---
+
+   These calls act on the type gpr_refcount.  It requires no destruction.  */
+
+/* Initialize *r to value n.  */
+GPRAPI void gpr_ref_init(gpr_refcount *r, int n);
+
+/* Increment the reference count *r.  Requires *r initialized. */
+GPRAPI void gpr_ref(gpr_refcount *r);
+
+/* Increment the reference count *r.  Requires *r initialized.
+   Crashes if refcount is zero */
+GPRAPI void gpr_ref_non_zero(gpr_refcount *r);
+
+/* Increment the reference count *r by n.  Requires *r initialized, n > 0. */
+GPRAPI void gpr_refn(gpr_refcount *r, int n);
+
+/* Decrement the reference count *r and return non-zero iff it has reached
+   zero. .  Requires *r initialized. */
+GPRAPI int gpr_unref(gpr_refcount *r);
+
+/* --- Stats counters ---
+
+   These calls act on the integral type gpr_stats_counter.  It requires no
+   destruction.  Static instances may be initialized with
+       gpr_stats_counter c = GPR_STATS_INIT;
+   Beware:  These operations do not imply memory barriers.  Do not use them to
+   synchronize other events.  */
+
+/* Initialize *c to the value n. */
+GPRAPI void gpr_stats_init(gpr_stats_counter *c, intptr_t n);
+
+/* *c += inc.  Requires: *c initialized. */
+GPRAPI void gpr_stats_inc(gpr_stats_counter *c, intptr_t inc);
+
+/* Return *c.  Requires: *c initialized. */
+GPRAPI intptr_t gpr_stats_read(const gpr_stats_counter *c);
+
+/* ==================Example use of interface===================
+   A producer-consumer queue of up to N integers,
+   illustrating the use of the calls in this interface. */
+#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
+}
+#endif
+
+#endif /* GRPC_IMPL_CODEGEN_SYNC_H */