1 // Copyright 2021 gRPC authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef GRPC_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H 16 #define GRPC_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H 17 18 #include <grpc/support/port_platform.h> 19 #include <inttypes.h> 20 #include <stddef.h> 21 22 #include <atomic> 23 24 #include "src/core/lib/debug/trace.h" 25 #include "src/core/util/debug_location.h" 26 27 // grpc_slice_refcount : A reference count for grpc_slice. 28 struct grpc_slice_refcount { 29 public: 30 typedef void (*DestroyerFn)(grpc_slice_refcount*); 31 NoopRefcountgrpc_slice_refcount32 static grpc_slice_refcount* NoopRefcount() { 33 return reinterpret_cast<grpc_slice_refcount*>(1); 34 } 35 36 grpc_slice_refcount() = default; 37 38 // Regular constructor for grpc_slice_refcount. 39 // 40 // Parameters: 41 // 1. DestroyerFn destroyer_fn 42 // Called when the refcount goes to 0, with 'this' as parameter. grpc_slice_refcountgrpc_slice_refcount43 explicit grpc_slice_refcount(DestroyerFn destroyer_fn) 44 : destroyer_fn_(destroyer_fn) {} 45 Refgrpc_slice_refcount46 void Ref(grpc_core::DebugLocation location) { 47 auto prev_refs = ref_.fetch_add(1, std::memory_order_relaxed); 48 GRPC_TRACE_LOG(slice_refcount, INFO) 49 .AtLocation(location.file(), location.line()) 50 << "REF " << this << " " << prev_refs << "->" << prev_refs + 1; 51 } Unrefgrpc_slice_refcount52 void Unref(grpc_core::DebugLocation location) { 53 auto prev_refs = ref_.fetch_sub(1, std::memory_order_acq_rel); 54 GRPC_TRACE_LOG(slice_refcount, INFO) 55 .AtLocation(location.file(), location.line()) 56 << "UNREF " << this << " " << prev_refs << "->" << prev_refs - 1; 57 if (prev_refs == 1) { 58 destroyer_fn_(this); 59 } 60 } 61 62 // Is this the only instance? 63 // For this to be useful the caller needs to ensure that if this is the only 64 // instance, no other instance could be created during this call. IsUniquegrpc_slice_refcount65 bool IsUnique() const { return ref_.load(std::memory_order_relaxed) == 1; } 66 67 private: 68 std::atomic<size_t> ref_{1}; 69 DestroyerFn destroyer_fn_ = nullptr; 70 }; 71 72 #endif // GRPC_SRC_CORE_LIB_SLICE_SLICE_REFCOUNT_H 73