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/*
*
* Copyright 2017 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_CORE_LIB_IOMGR_CALL_COMBINER_H
#define GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H
#include <stddef.h>
#include <grpc/support/atm.h>
#include "src/core/lib/iomgr/closure.h"
#include "src/core/lib/iomgr/exec_ctx.h"
#include "src/core/lib/support/mpscq.h"
// A simple, lock-free mechanism for serializing activity related to a
// single call. This is similar to a combiner but is more lightweight.
//
// It requires the callback (or, in the common case where the callback
// actually kicks off a chain of callbacks, the last callback in that
// chain) to explicitly indicate (by calling GRPC_CALL_COMBINER_STOP())
// when it is done with the action that was kicked off by the original
// callback.
extern grpc_core::TraceFlag grpc_call_combiner_trace;
typedef struct {
gpr_atm size; // size_t, num closures in queue or currently executing
gpr_mpscq queue;
// Either 0 (if not cancelled and no cancellation closure set),
// a grpc_closure* (if the lowest bit is 0),
// or a grpc_error* (if the lowest bit is 1).
gpr_atm cancel_state;
} grpc_call_combiner;
// Assumes memory was initialized to zero.
void grpc_call_combiner_init(grpc_call_combiner* call_combiner);
void grpc_call_combiner_destroy(grpc_call_combiner* call_combiner);
#ifndef NDEBUG
#define GRPC_CALL_COMBINER_START(call_combiner, closure, error, reason) \
grpc_call_combiner_start((call_combiner), (closure), (error), __FILE__, \
__LINE__, (reason))
#define GRPC_CALL_COMBINER_STOP(call_combiner, reason) \
grpc_call_combiner_stop((call_combiner), __FILE__, __LINE__, (reason))
/// Starts processing \a closure on \a call_combiner.
void grpc_call_combiner_start(grpc_call_combiner* call_combiner,
grpc_closure* closure, grpc_error* error,
const char* file, int line, const char* reason);
/// Yields the call combiner to the next closure in the queue, if any.
void grpc_call_combiner_stop(grpc_call_combiner* call_combiner,
const char* file, int line, const char* reason);
#else
#define GRPC_CALL_COMBINER_START(call_combiner, closure, error, reason) \
grpc_call_combiner_start((call_combiner), (closure), (error), (reason))
#define GRPC_CALL_COMBINER_STOP(call_combiner, reason) \
grpc_call_combiner_stop((call_combiner), (reason))
/// Starts processing \a closure on \a call_combiner.
void grpc_call_combiner_start(grpc_call_combiner* call_combiner,
grpc_closure* closure, grpc_error* error,
const char* reason);
/// Yields the call combiner to the next closure in the queue, if any.
void grpc_call_combiner_stop(grpc_call_combiner* call_combiner,
const char* reason);
#endif
/// Registers \a closure to be invoked by \a call_combiner when
/// grpc_call_combiner_cancel() is called.
///
/// Once a closure is registered, it will always be scheduled exactly
/// once; this allows the closure to hold references that will be freed
/// regardless of whether or not the call was cancelled. If a cancellation
/// does occur, the closure will be scheduled with the cancellation error;
/// otherwise, it will be scheduled with GRPC_ERROR_NONE.
///
/// The closure will be scheduled in the following cases:
/// - If grpc_call_combiner_cancel() was called prior to registering the
/// closure, it will be scheduled immediately with the cancelation error.
/// - If grpc_call_combiner_cancel() is called after registering the
/// closure, the closure will be scheduled with the cancellation error.
/// - If grpc_call_combiner_set_notify_on_cancel() is called again to
/// register a new cancellation closure, the previous cancellation
/// closure will be scheduled with GRPC_ERROR_NONE.
///
/// If \a closure is NULL, then no closure will be invoked on
/// cancellation; this effectively unregisters the previously set closure.
/// However, most filters will not need to explicitly unregister their
/// callbacks, as this is done automatically when the call is destroyed.
void grpc_call_combiner_set_notify_on_cancel(grpc_call_combiner* call_combiner,
grpc_closure* closure);
/// Indicates that the call has been cancelled.
void grpc_call_combiner_cancel(grpc_call_combiner* call_combiner,
grpc_error* error);
#endif /* GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H */
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