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// Copyright 2021 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_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H
#define GRPC_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H
#include <grpc/support/port_platform.h>
#include <inttypes.h>
#include <stddef.h>
#include <atomic>
#include <grpc/support/log.h>
#include "src/core/lib/debug/trace.h"
#include "src/core/lib/gprpp/debug_location.h"
extern grpc_core::DebugOnlyTraceFlag grpc_slice_refcount_trace;
// grpc_slice_refcount : A reference count for grpc_slice.
struct grpc_slice_refcount {
public:
typedef void (*DestroyerFn)(grpc_slice_refcount*);
static grpc_slice_refcount* NoopRefcount() {
return reinterpret_cast<grpc_slice_refcount*>(1);
}
grpc_slice_refcount() = default;
// Regular constructor for grpc_slice_refcount.
//
// Parameters:
// 1. DestroyerFn destroyer_fn
// Called when the refcount goes to 0, with 'this' as parameter.
explicit grpc_slice_refcount(DestroyerFn destroyer_fn)
: destroyer_fn_(destroyer_fn) {}
void Ref(grpc_core::DebugLocation location) {
auto prev_refs = ref_.fetch_add(1, std::memory_order_relaxed);
if (grpc_slice_refcount_trace.enabled()) {
gpr_log(location.file(), location.line(), GPR_LOG_SEVERITY_INFO,
"REF %p %" PRIdPTR "->%" PRIdPTR, this, prev_refs, prev_refs + 1);
}
}
void Unref(grpc_core::DebugLocation location) {
auto prev_refs = ref_.fetch_sub(1, std::memory_order_acq_rel);
if (grpc_slice_refcount_trace.enabled()) {
gpr_log(location.file(), location.line(), GPR_LOG_SEVERITY_INFO,
"UNREF %p %" PRIdPTR "->%" PRIdPTR, this, prev_refs,
prev_refs - 1);
}
if (prev_refs == 1) {
destroyer_fn_(this);
}
}
// Is this the only instance?
// For this to be useful the caller needs to ensure that if this is the only
// instance, no other instance could be created during this call.
bool IsUnique() const { return ref_.load(std::memory_order_relaxed) == 1; }
private:
std::atomic<size_t> ref_{1};
DestroyerFn destroyer_fn_ = nullptr;
};
#endif // GRPC_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H
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