synchronization/internal/create_thread_identity.h

0001 /*
0002  * Copyright 2017 The Abseil Authors.
0003  *
0004  * Licensed under the Apache License, Version 2.0 (the "License");
0005  * you may not use this file except in compliance with the License.
0006  * You may obtain a copy of the License at
0007  *
0008  *      https://www.apache.org/licenses/LICENSE-2.0
0009  *
0010  * Unless required by applicable law or agreed to in writing, software
0011  * distributed under the License is distributed on an "AS IS" BASIS,
0012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0013  * See the License for the specific language governing permissions and
0014  * limitations under the License.
0015  */
0016
0017 // Interface for getting the current ThreadIdentity, creating one if necessary.
0018 // See thread_identity.h.
0019 //
0020 // This file is separate from thread_identity.h because creating a new
0021 // ThreadIdentity requires slightly higher level libraries (per_thread_sem
0022 // and low_level_alloc) than accessing an existing one.  This separation allows
0023 // us to have a smaller //absl/base:base.
0024
0025 #ifndef ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_
0026 #define ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_
0027
0028 #include "absl/base/internal/thread_identity.h"
0029 #include "absl/base/port.h"
0030
0031 namespace absl {
0032 ABSL_NAMESPACE_BEGIN
0033 namespace synchronization_internal {
0034
0035 // Allocates and attaches a ThreadIdentity object for the calling thread.
0036 // For private use only.
0037 base_internal::ThreadIdentity* CreateThreadIdentity();
0038
0039 // Returns the ThreadIdentity object representing the calling thread; guaranteed
0040 // to be unique for its lifetime.  The returned object will remain valid for the
0041 // program's lifetime; although it may be re-assigned to a subsequent thread.
0042 // If one does not exist for the calling thread, allocate it now.
0043 inline base_internal::ThreadIdentity* GetOrCreateCurrentThreadIdentity() {
0044   base_internal::ThreadIdentity* identity =
0045       base_internal::CurrentThreadIdentityIfPresent();
0046   if (ABSL_PREDICT_FALSE(identity == nullptr)) {
0047     return CreateThreadIdentity();
0048   }
0049   return identity;
0050 }
0051
0052 }  // namespace synchronization_internal
0053 ABSL_NAMESPACE_END
0054 }  // namespace absl
0055
0056 #endif  // ABSL_SYNCHRONIZATION_INTERNAL_CREATE_THREAD_IDENTITY_H_